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Effects of changes in martensite and carbide induced by laser shock peening (LSP) on tensile properties and stress corrosion behaviors of 2Cr13 martensitic stainless steel (MSS) were investigated. Results indicated that LSP not only caused plastic deformation of the martensite and carbide but also brittle deformation of carbide. Based on fine/coarse grain heterostructure, carbide plastic and brittle deformation, carbide local decomposition, compressive residual stress and grain coarsening caused by tensile stress, 14.7 % and 44.5 % increase in the strength and ductility in NaCl solution are respectively achieved for MSS with a surface where the formation of corrosion pits is significantly suppressed. [Display omitted] • LSP induced plastic deformation of the martensite and carbide as well as brittle deformation of carbide. • LSP induced significant improvement in strength, ductility, and stress corrosion resistance. • Second phase strengthening generated by carbide fragmentation promotes the strength improvement. • Heterostructure, plastic and carbides and grain coarsening contribute to the ductility enhancement. • Compared with the AR sample, the number and size of LSP-induced corrosion pits of MSS decreased. • Carbide decomposition, grain refinement and compressive residual stress suppress the corrosion process. [ABSTRACT FROM AUTHOR]

In present work, ultrasonic surface rolling (USR) is applied to DD6 Ni-based single crystal (NBSC) superalloys, and the thermal relaxation behavior of the pre-treated alloys are investigated at 650 °C. Combined with mechanical properties, the plastic deformation and recovery mechanisms of the hardened layers are revealed in detail. Results show that compressive residual stress amplitude of 1163 MPa, 75.1 % improvement of surface nano-hardness and 83.02 % reduction on surface roughness are achieved by USR. Both deformed layer thickness and slip density progressively increases with USR cycles, where initial octahedron {111}<110> slips transform to a mixture of octahedron {111}<110> and dodecahedron {111}<112> slips. Meanwhile, shear step length expansions form γ′ segment/γ terminal interface with superlattice extrinsic stacking fault (SESF) on 1 ¯ 11 , which may have inferior energy threshold for γ dislocation invasions than primary ones through shortening mean free path. Also, this drives γ′/γ solute mingling to induce tortuous interfaces. While dislocation proliferation dominates γ channel hardening, the γ′ hardening derives from planar fault strengthening and net system energy augmentation. During thermal exposure, surface integrities of USRed DD6 are strongly degraded, attributable to slip trace elimination and local γ′ coarsening. Thermal exposure further compels the γ dislocation to migrate towards γ′ segment across γ′ segment/γ terminal interface. Then, they are probably consumed to motivate solutes to phase boundary to reshape the γ′ morphologies through interface rearrangements under the assistance of γ dislocation network. The orientation transformation of SESF on 1 ¯ 11 to 010 and the mixture of SESF and superlattice intrinsic stacking fault on 1 ¯ 11 are thought to be possible manipulated mechanisms for γ′ coarsening, significant impairing the work hardening of alloy due to interfacial coherency deterioration. This paper could provide guidance for USR strengthening designs of NBSC. • USR induces CRS and nano-hardness gradients on the DD6 surface via slip activation. • Raised shear step length form secondary γ′/γ interface to promote solute diffusion. • Matrix dislocations invade into γ′ particle preferentially across newborn interface. • Thermal exposure degrades surface integrities by slip elimination and γ′ coarsening. • Local γ′ coarsening are manipulated by the orientation transformation of SESF/SISF. [ABSTRACT FROM AUTHOR]

The mechanical properties and thermal shock resistance of plasma-sprayed 56 wt% Y 2 O 3 -stabilized ZrO 2 thick thermal barrier coatings (TTBCs) deposited with different critical plasma spraying parameter (CPSP) values and its stress evolution were investigated. With the CPSP value increased from 0.83 kW·SLPM−1 to 1.17 kW·SLPM−1, the porosity was decreased from 14.62 ± 0.84 % to 7.00 ± 0.38 % while the bonding strength was increased from 7.82 ± 0.64 MPa to 9.95 ± 0.30 MPa. As a result, the hardness of the coating obtained from the cross-section was increased from 2.16 ± 0.61 GPa to 2.67 ± 0.82 GPa, and the elastic modulus was also increased from 60.47 ± 5.22 GPa to 71.93 ± 6.91 GPa. During thermal cycling test at 1000 °C, thermal cycling lifespan presented a decrease from (83 ± 3) cycles to (44 ± 3) cycles, and coating failure was mainly attributed to the occurrence of partial or whole spallation of the top coat. According to the stress simulation result, residual stress in the coating was accumulated while thermal stress was released with the increase of thermal cycles, and the increasing residual stress was the main failure driver for the coating. • 56YSZ coatings with a thickness of ∼1000 μm were successfully prepared onto the nickel-based superalloy. • The structure and properties of the coating were optimized by adjusting critical plasma spraying parameters. • The influence of critical plasma spraying parameters on mechanical properties and microstructure was considered in the finite element model. [ABSTRACT FROM AUTHOR]

Numerous peening techniques exist can effectively modify the sample surface, although at the expense of severe surface damage and high capital investment. Ultrasonic-assisted abrasive peening (UAP) is a superior option that can peen the surface with minimal deterioration using a basic probe sonicator. In this paper, the influence of UAP parameters (i.e., beaker size and fluid volume, power, abrasive concentration, and time) on the surface integrity of Ti-6Al-4V and OFHC Cu was studied experimentally. The process is capable of inducing significant compressive residual stress at around 84 % and 280 % of yield strength in Ti-6Al-4V and OFHC Cu, respectively. The study examined the change in surface roughness (ΔR a), ΔR a = roughness before - roughness after peening. As peening intensities increase, ΔR a reaches +7 nm, showing a surface finish in Ti-6Al-4V. The dislocations density calculated from the Williamson-Hall equation exhibited a 20 and 4.5-fold augmentation in peened Ti-6Al-4V and OFHC Cu in comparison to their un-peened state. EBSD analysis revealed a 28 % and 40 % reduction in grain size in Ti-6Al-4V and OFHC Cu after peening. This work validates the efficacy of the proposed UAP technique and supports the selection of optimized UAP process parameters. [Display omitted] • Addition of SiC abrasives to DI water enhanced the residual stress by 19 %. • 40 % of peening fluid in beaker by volume showed maximum residual stress. • Higher peening intensities yielded surface roughness, ΔR a of +7 nm. • A 20 μm and 90 μm grain refinement layer in Ti6Al4V and Copper were found. [ABSTRACT FROM AUTHOR]

This study examines the residual stress, microstructure, and stress-induced phase transformation of TC17 titanium alloy after different shot peening processes. A comprehensive analysis of the unique impact of shot peening on α-Ti and β-Ti was performed. The results indicate a substantial reduction in the grain size of the deformed layer and the creation of a high density of dislocations. Additionally, increased peening intensity results in decreased grain size, and multiple shot peening promotes further reduction in grain size. Compressive residual stresses were detected in the deformed layer, and multiple shot peening significantly augmented the residual stresses in the surface and near-surface regions. In particular, the highest compressive residual stresses after triple shot peening treatments were measured at −1079 MPa (at a depth of 10 μm for α-Ti) and −792 MPa (at a depth of 50 μm for β-Ti). In addition, multiple shot peening can significantly reduce surface roughness and enhance surface nanocrystallization when approximate surface residual stresses are obtained. Remarkably, the use of single shot peening revealed parallel stacking faults in certain α-Ti samples. However, under multiple shot peening, these stacking faults evolved into face-centered cubic Ti (FCC-Ti) with broader widths and a greater number. The stress-induced phase transition orientation relation was determined to be (0001) HCP //(1 1 ¯ 1) FCC and [2 1 ¯ 1 ¯ 0] HCP //[011] FCC , with α-Ti grains being interspersed with FCC-Ti, thus promoting additional grain refinement. • TC17 titanium alloy was subjected to multiple shot peening treatments, which resulted in the formation of thicker nanocrystalline layers and a significant increase in compressive stress compared to conventional shot peening treatment. • Residual stress and microstructure character were evaluated by XRD line profile analysis. • Relationship exists between the formation of face-centered cubic Ti and the microstrain at the surface. [ABSTRACT FROM AUTHOR]

The near-equatomic NiTi shape memory alloy demonstrates exceptional damping performance due to its distinctive low-temperature self-cooperative martensitic internal friction. This study successfully fabricated NiTi-NAB (Nickel-Aluminium bronze shape memory alloy) functionally graded composite coatings with excellent metallurgical bonding between layers on Q235 steel substrates by designing an appropriate interlayer structure and employing the high-speed laser-directed energy deposition (LDED). Through comprehensive evaluation of the composite coating's performance and the numerical simulations of heat transfer within the molten pool, we elucidated the impact of process parameter levels on the microstructure and phase transformation characteristics of the NiTi alloy coating (NTC). The phase composition and phase interface characteristics of the NTC surface and bonding interface were analyzed using an electron probe microanalyzer and transmission electron microscopy, while dynamic thermomechanical analysis was employed to evaluate the damping performance of the NTC. The results indicate that an optimal parameter combination area still exists within the NTC-LDED process parameter window, even with equal laser energy density. Insufficient parameter levels can lead to an increase of micro-defects within the NTC, consequently causing a deterioration in both the cohesion and deformation resistance of the coating. Excessively high parameter levels can lead to significant element loss and residual stress, which in turn contributes to an increase in microcracks within the coating. A considerable quantity of reaction product mixture phases was formed at the interface between NTC and NAB, tending to align coherently with the NAB phase interface. The NTC, prepared with optimal process parameters, exhibits exceptional damping performance with a damping ratio of 0.498 at internal friction equilibrium, rendering it highly promising for applications in surface erosion protection for fluid machinery. • The NiTi alloy coating stabilizes in the B19′ phase at ambient temperature. • The impact of molten pool traits on NiTi alloy coatings' properties was uncovered. • The atoms at the NiTi-NAB interface tend to arrange themselves coherently. • The damping ratio of the NiTi alloy coating hits 0.498 post-internal friction balance. [ABSTRACT FROM AUTHOR]

Graphene was proven to be an excellent surface-strengthening material. However, there needs to be more literature explaining its strengthening mechanism at the atomic level. This study systematically investigated the surface strengthening mechanism of graphene coating on the Al 0.3 CoCrFeNi high-entropy alloy (HEA) and the influence of loading-unloading cycles on the formation of internal defects in the material through molecular dynamics (MD) simulations at the atomic level. Research results show that the internal stress concentration in HEA without graphene coating leads to a more considerable residual depth after unloading. With the addition of a graphene coating, the material's stress area increases, effectively alleviating stress concentration and reducing residual depth. Furthermore, the lengths of Lomer-Cottrell dislocation locks and Hirth dislocation locks inside the material increase, enhancing the material's deformation resistance. The more layers of graphene, the larger the stress distribution area and the greater the hardness. Under the same indentation force, the number of HCP structures and amorphous structures inside the material is inversely proportional to the thickness of the graphene layers. In addition, after multiple loading and unloading cycles, the hardness of HEA/GP materials basically remains unchanged, while internal defects increase and residual depth increases. • The enhancement mechanism of graphene coating on Al 0.3 CoCrFeNi high-entropy alloy is being studied through MD simulations of nanoindentation. • The effect of loading-unloading cycle numbers on the propagation of internal stress and strain in materials is being examined. • Graphene coatings alleviate stress concentration in HEA by increasing the contact area and reducing residual stress. • After adding graphene, more dislocation cells and dislocation locks are forming in the HEA matrix. • After multiple loading-unloading cycles, the region of contact with the indenter in HEA fails first. [ABSTRACT FROM AUTHOR]

Wear-resistant thin films on cutting tools require effective ion etching to enhance adhesion and thus extended tool service life. Arc enhanced glow discharge (AEGD) ion etching, characterized by high ionization degrees and high etch rates, was applied to ultrafine-grained WC-Co cemented carbide, commonly used for micromilling cutters. The effect of AEGD ion etching on the surface integrity of WC-Co and the resulting adhesion behavior of a TiAlSiN thin film was investigated by varying the etching time in comparison with conventional glow discharge (GD) ion etching. In addition, the impact of intensive etching on the cutting edge geometry of micro end cutters and, in turn, on the cutting performance in micromilling of hardened and annealed high-speed steel was evaluated. AEGD achieves remarkable etch rates of 12 nm/min at extended etching times, which are 100 times greater than conventional glow discharge (GD) ion etching. Prolonged AEGD ion etching for ≥30 min removes entire near-surface WC grains and exposes carbides beneath, resulting in increased surface roughness. After the etching process, polished WC-Co substrates exhibit a slight reduction in residual compressive stresses, which steadily decrease with increasing AEGD ion etching time. Furthermore, a TiAlSiN thin film demonstrates high adhesion on AEGD-etched surfaces compared to GD ion etching. Even a brief 5 min AEGD ion etching ensures the highest adhesion class according to the Rockwell C indentation test. Moreover, the intensive material removal results in significant changes in cutting edge geometry of micro end cutters, yielding substantial cutting edge rounding and an asymmetrical shape with form-factors Κ ≥ 2. In cutting tests, the resulting cutting edge geometries effectively reduce the wear formation and the associated wear-related increase in process forces during micromilling hardened and tempered powder metallurgical high-speed steel. In summary, AEGD ion etching emerges as a highly effective method for both enhancing thin film adhesion and preparing adapted asymmetrical cutting edge geometries for micromilling tools. [Display omitted] • AEGD ion etching achieves 100-fold increase in etch rate compared to GD ion etching. • AEGD leads to increased surface roughness with longer etching times. • Improved adhesion of HiPIMS-TiAlSiN thin film on WC-Co with AEGD ion etching • AEGD ion etching creates asymmetrical cutting edge geometries of micro end mills. [ABSTRACT FROM AUTHOR]

Post-processing of tool coatings is an essential way to remove defects, enhance coating properties, and improve tool performance, where abrasive jet machining plays an important role. This paper introduces a novel application of self-developed elastic abrasives to the post-treatment of coated tools, with a comparison against hard abrasive (Al 2 O 3) jet machining (HAJM). The results demonstrate that EAJM significantly reduces the surface roughness of the coating and enhances the wear resistance of milling tools across a wide range of jetting parameters without damaging the coating. Conversely, HAJM yields more pronounced improvements in physical properties such as coating hardness, elastic modulus, and residual stress, and also significantly enhances tool performance, albeit with a need for precise process parameters. Overly aggressive HAJM parameters can lead to diminished coating performance and reduced tool life. Additionally, the study reveals that the improvement in tool life is closely linked to the physical properties of the coating, which contributes to the enhanced performance observed with HAJM-treated tools. To further investigate this, a mathematical model was established to analyze the coupling effect of jet pressure and time on tool life. The proposed model identifies the optimal ranges of the jetting coefficient for HAJM and EAJM as 326–4870 kPa·s and 1061–17,780 kPa·s, respectively, offering a novel approach to optimizing tool performance and life. • The newly-developed elastic abrasive is employed for abrasive jet machining. • A comparison between elastic and hard abrasives for post-treatment of tool coatings. • Surface integrity of coatings and cutting performance of tools under different post-processes are investigated. [ABSTRACT FROM AUTHOR]

Herein, nanocrystalline NbMoTaW and (NbMoTaW)N thin films were prepared via magnetron sputtering and investigated using nanoindentation creep tests at various indentation loads (P). The hardness (H) of films increases with P , exhibiting an abnormal indentation size effect (ISE). At the same time, with decreasing indentation depth (h), the creep rate and the creep rate sensitivity (m) both increase. Under a critical h (h c) for each film, m sharply increases. The diffusion between the indenter/film interface dominates the creep mechanism at h lower than h c , whereas the dislocation–grain boundary interaction dominates the creep deformation at h higher than h c. The coble creep and lattice diffusion were both excluded as the main deformation mechanism. The escape of screw dislocations to the surface leads to the softening of the film, whereas the pile-up of screw dislocations leads to hardening, explaining the abnormal ISE on H. The effect of residual stress, grain boundary structures, substrate, and impurities are also discussed. • Nanocrystalline NbMoTaW and (NbMoTaW)N films were prepared. • Hardness of each films increases with increasing indentation depth. • Hardness with indentation depth exhibits an abnormal indentation size effect. • The strenghening mechanism is screw dislocation pile-up at grain boundaries. • The creep rate sensitivity decreases with increasing indentation depth. [ABSTRACT FROM AUTHOR]

The aim of this study is to improve the fatigue limit of thermally sprayed EN 1.0032 steel substrates by combining turning, diamond smoothing, and temperature regulation during wire arc spraying of Ni-5wt%Al. In contrast to conventional shot peening, diamond smoothing induces defined and uniformly distributed compressive residual stresses, which will allow for an improved fatigue limit. In addition, the spraying process is observed using an infrared camera to study the influence of cooling between each layer application. The microstructure, phases, and residual stresses are examined by scanning electron microscopy (SEM) and X-ray diffraction. The uncoated and coated specimens are investigated regarding their quasi-static and high-cycle fatigue (HCF) behavior. After the HCF tests, the fracture surfaces are analyzed by stereomicroscopy and SEM. Diamond smoothing increases the fatigue limit in contrast to solely turned surfaces by 4.3 %. Furthermore, continuous thermal spraying of diamond smoothed surfaces reduces the fatigue limit. Cooling between the single-layer applications improves the fatigue limit but cannot compensate for all tensile residual stresses introduced by thermal spraying. The results of the present study show a first positive trend to increase the fatigue limit of thermally sprayed parts using diamond smoothing for pre-machining of a steel substrate and the temperature regulation during wire arc spraying. However, further studies are needed to improve the fatigue limit, as it seems that the compressive residual stresses induced by diamond smoothing with the parameters used are too small. • Diamond smoothing before thermal spraying was examined. • Diamond smoothing increases the fatigue limit. • Thermal spraying reduces the fatigue limit. • Cooling between each layer application slightly increases the fatigue limit. [ABSTRACT FROM AUTHOR]

The interrupted discrete waterjet (DWJ) offers advantages in surface treatment due to its exceptional load characteristics and high controllability. However, the surface characteristics of materials under controllable DWJ parameters have not been fully elucidated. This study delves into the surface morphology, roughness parameters, microhardness, residual stress, and distribution of crystal characteristics in both the depth and radial directions under 2400–36,000 impact cycles of DWJ through peening experiments and material characterization. The findings indicate that the surface morphology is influenced by high-frequency roughness components with limited impact cycles, while low-frequency waviness components gradually take precedence with more impact cycles. As impact cycles increase, certain roughness parameters such as Sq , S5p , S5v , and S10z initially rise until 21,600 cycles, after which they fluctuate within a specific range. Furthermore, DWJ peening leads to an increase in maximum hardness with impact cycles, with the depth of peak value transitioning from the surface layer to the subsurface. The residual compressive stress initially increases and then decreases with impact cycles. Under the experimental conditions, the maximum hardness reaches 268.1HV0.3, a 49.95 % increase from the original state, and the peak residual compressive stress reaches 297.7 MPa with a 310.2 % increase. As impact cycles continue to rise, a balance between material removal and surface hardening is achieved, resulting in the stabilization of maximum hardness and compressive stress as erosion strength grows. Following DWJ peening, there is an increase in the percentage of low-angle grain boundaries, along with enhanced grain refinement, increased geometrically necessary dislocation (GND) density, and the emergence of new phases. As the impact cycles increase, the effects of DWJ peening on crystal grains become more pronounced. Additionally, it has been observed that the lateral jetting influence extends further horizontally than in the depth direction of the incoming jet. It is considered that cyclic hardening and high strain rate effects (1.2 × 104) play significant roles in material hardening and failure. • The study reveals the changes of morphology, hardness, residual stress, and crystal structure as impact cycles increase. • Surface topography initially shows high-frequency roughness, shifting to waviness with increased impacts. • Maximum hardness increases with impact cycles, while residual compressive stress first rises, then falls. • Increasing impact cycles causes a balance between material removal and surface hardening. • The influence of lateral jet on crystal structure exceeds that of the incident jet in horizontal range. [ABSTRACT FROM AUTHOR]

A number of industrial applications today require thermally sprayed coatings that exhibit good adhesion, high temperature and chemical resistance, and can withstand particle impacts or dynamic interactions with components. A common example of a high-velocity oxygen fuel (HVOF) sprayed coating with such the aforementioned properties is Cr 3 C 2 –25%NiCr. The objective of this study is to examine the impact of varying thicknesses and surface roughness on the impact lifetime and impact wear of Cr 3 C 2 –25%NiCr coatings. A series of Cr 3 C 2 –25%NiCr coatings were subject to analysis using a dynamic impact tester with impact loads of 200 N, 400 N, and 600 N. The results indicated that there exists an optimal coating thickness with the highest impact lifetime. The results were discussed using microstructural analysis of the impact coatings and finite element simulation. The maximum impact lifetime was achieved with the optimal combination of sample material properties, substrate mechanical properties, coating thickness, and residual stress. Furthermore, it was demonstrated that surface does not influence the impact lifetime of the coating, but does affect the accuracy of its determination. • Impact lifetime of Cr 3 C 2 –25%NiCr coatings with various parameters was investigated. • The impact behaviour was discussed using structural analysis and FEM simulations. • Internal cohesion failure occurred before surface cracking was visible. • A local maximum of the impact lifetime was found at the optimal coating thickness. • The surface roughness affects the precision of impact lifetime evaluation. [ABSTRACT FROM AUTHOR]

Combined shot peening and laser shock peening (CSP) can introduce high surface compressive residual stress (CRS) and deep CRS layer, and reduce the high surface roughness caused by shot peening. The relationship between CSP sequences and surface integrity, including CRS and surface roughness, is far from satisfying the actual demand. In this paper, we construct a finite element model considering initial surface profile features. The experimental results agree with the simulated results. Based on the simulation results, axial and longitudinal stress wave transfer effects on surface CRS and depth CRS are investigated. Compared with shot peening (SP) and laser shock peening (LSP) alone, CSP treatment can increase CRS depth and CRS magnitude by 1060 μm and 50 ∼ 80Mpa, respectively. In addition, the roughness following CSP treatment is lower than that observed after SP treatment alone, and the roughness varies depending on the sequence of CSP treatment. Specifically, the roughness values for SP, SP + LSP, and LSP + SP are 0.938 ± 0.031 μm, 0.982 ± 0.11 μm, and 1.168 ± 0.093 μm, respectively. The surface morphology, hardness, and simulation results are combined to reveal the reasons for the reduction of surface roughness after CSP treatment. The changes of peaks and valleys after CSP treatment compared with single SP treatment were studied, and the variation trend of surface roughness was further explained. • A three-dimensional finite element model with real initial surface roughness is constructed. • The axial and longitudinal stress wave transfer on surface CRS and depth CRS are investigated. • The variation mechanism of surface roughness after CSP treatment is revealed. • The changes of peak and valley after CSP treatment compared with single SP treatment are investigated. [ABSTRACT FROM AUTHOR]

Surface nanocrystallization together with compressive residual stresses can significantly improve the mechanical properties of metallic materials. An innovative surface process called magnetic-assisted ultrasonic nanocrystal surface modification (MA-UNSM) is reported here. By coupling integrates magnetoplasticity and shocking-induced plasticity, the MA-UNSM can enhance the plastic deformation capability of materials without significantly increasing the USNM processing temperature, thus realizing more effective grain refinement, deeper plastic-affected depth and higher-magnitude residual stresses, as evidenced by microscopic characterization and mechanical measurements. Our results demonstrated that the magnetic field improves the plasticity of the material by reducing the resistance between dislocations and pinning obstacles and thus enhances the effectiveness of ultrasonic peening treatment. Magnetic field with two intensities (0.25 T and 0.6 T) were used to assist UNSM, and the results showed that 0.6 T was the better condition. • MA-UNSM demonstrates superior processing efficiency over UNSM. • Magnetic field improved Ti64 alloy plasticity, revealed by hardness tests. • Magnetic field improves plasticity by reducing dislocation depinning resistance. [ABSTRACT FROM AUTHOR]

As a commonly used surface strengthening technology, shot peening, which can significantly improve the fatigue strength of mechanical parts, is widely used in the fields of vehicles and aviation. To obtain a larger residual compressive stress and further refine the grain size under normal shot peening intensity and coverage, this study proposes an induction heating composite shot peening (IHCSP) surface strengthening method, aiming to utilize the coupling effect of temperature and stress fields to promote the shot peening strengthening effect. An IHCSP test plan was designed and an IHCSP test bench was created to achieve simultaneous induction heating and shot peening. This study compares the surface integrity parameters and microstructures under three processes: un-peened, conventional shot peening, and IHCSP. The results show that the maximum axial and radial compressive residual stresses increase by 72.41 and 75.4 MPa respectively; the depth of the hardened layer increases by 0.3 mm, the martensitic transformation more complete, the grain size decreases by 483 nm, the dislocation density increases significantly, and nanocrystals are obtained on the surface of the material. These results verify the superiority of IHCSP surface strengthening. • Proposed an induction heating composite shot peening (IHCSP) strengthening method and created an IHCSP test bench • IHCSP increases surface residual compressive stress and the layer depth of the residual compressive stress. • IHCSP increased the surface microhardness and hardened layer depth. • IHCSP promotes martensitic transformation. • IHCSP obtained nanocrystals, refined grain size, and increased dislocation density on the material surface. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a solid state deposition presented in the literature to produce coatings for various applications, e.g., corrosion-resistant 316L stainless steel, Ti light alloy parts repairing, and hydrophobic Cu coatings. CS sprays particles under high velocity, impacting onto a prepared surface or substrate, and the powders bond by a severe and fast plastic deformation, consolidating the coating layer by layer. The number of layers depends on the designed coating thickness since each powder and CS parameters results in a different layer thickness. This work evaluates three feedstock powders (Cu, Ti, and 316L) for CS processing, and the characteristics and properties of the CS-ed coatings, studying the effects of the thickness coatings on their microstructure, porosity, hardness, adhesion to the substrate, and residual stress generated. The images of microstructures were obtained by optical microscopy and SEM, and the near-to-surface residual stress was measured by X-ray diffraction (XRD). Increasing the coating thickness produced a substrate deformation due to the compressive residual stress dominating the coating, which is numerically obtained and proven by XRD. Besides that, increasing the coating thickness slight increased the deposition efficiency for Cu ant Ti, but went in the opposite way for 316L; reduced the coating adhesion to the substrate; and did not altered significantly the hardness. • For CS-ed Cu, Ti, and 316L coatings on carbon steel, the thickness did not alter the residual stress; • The substrate material and properties alter the CS Cu, Ti, and 316L coating deposition efficiency on carbon steel. [ABSTRACT FROM AUTHOR]

Gas-nitriding was performed to enhance the surface hardness and fatigue performance of 4140 steel pre-treated with micro-shot peening (MSP). The 4140 steel was solutionized and tempered at 200 °C/1 h, named as the base metal (BM) with the hardness of 500 HV 0.05. Some BM samples were subjected to MSP (i.e., SPBM), and subsequently gas-nitrided at 520 °C/6 h (i.e., NBM). A compound layer of about 10 μm thickness formed on the surface of the NBM sample consisted of nano-grained Fe 3 N and Fe 4 N. The NBM sample showed a decline in hardness from the nitrided surface (750 HV 0.05) to the matrix (300 HV 0.05). In the as-peened condition, the peak residual compressive stress (RCS) was close to −500 MPa, and a very shallow stress field was obtained. After gas-nitriding, the peak RCS decreased to less than −400 MPa, while the affected depth expended to 300 μm. Defects in the compound layer did not deteriorate the fatigue strength/life of the nitrided 4140 steel. The RCS field effectively suppressed fatigue crack initiation and propagation at the surface of the NBM and SPBM samples. By contrast, surface cracks resulted in the fatigue failure of the BM sample. • Gas-nitriding of 4140 steel pre-treated by micro-shot peening (MSP) was studied. • MSP introduced residual compressive stress (RCS) and refined structure. • Nano-grained Fe 3 N and Fe 4 N were formed in the compound layer. • The RCS field became deeper after gas-nitriding. • The sub-surface inclusions caused the fatigue failure of nitrided 4140 steel. [ABSTRACT FROM AUTHOR]

Typically, a cost-effective and versatile carburizing process is used to improve the surface integrity of high-value-added gear components. In this study, carburized treatment and wet shot peening (WSP) were applied to increase the corrosion resistance of 18CrNiMo7-6 gear steel. The surface integrity and corrosion resistance after carburizing and combined treatment (carburized treatment + WSP) were analyzed. The results indicated that the combined treatment converted the retained austenite surface layer within approximately 45 μm from the surface into the martensitic phase, with a 13.9 % reduction in equivalent grain size and a 23.6 % increase in dislocation density compared with carburizing. Furthermore, electrochemical experiments in a 3.5 wt% NaCl solution indicated that the combined treatment process increased the corrosion resistance compared with carburizing (55.4 % lower corrosion current density and a higher Fe2+/Fe3+ ratio). Despite the high surface roughness obtained with combined treatment, the improved corrosion resistance is primarily ascribed to the high compressive residual stress and dislocation density. This study provides insights into the surface strengthening design of 18CrNiMo7-6 gear steel for corrosive environments—particularly the synergistic strengthening effect of carburizing and WSP. • WSP was introduced to improve corrosion resistance and surface integrity. • Corrosion resistance of 18CrNiMo7-6 steel cannot be enhanced by carburized treatment. • Competing effects of surface integrity on corrosion resistance were investigated. [ABSTRACT FROM AUTHOR]

To improve the adhesion strength and enhance the wear resistance of diamond-like carbon (DLC) coatings, different negative bias voltages were utilized to deposit a-Si:C:H/H-DLC/DLC composite coatings on the 45 steel substrates using direct current plasma enhanced chemical vapor deposition technology. Influences of negative bias voltages on the surface morphology, microstructure, mechanical properties, and tribological performance were investigated. The results showed that as the bias voltages increased from −400 V to −600 V, the surface roughness and thickness of the coatings increased, reaching a maximum roughness of 0.426 μm and a maximum total thickness of 9.9 μm. Raman data illustrated the decrease of hydrogen contents and the increase in sp3 bonds content, matching well with the increasing hardness and elastic modulus. The residual stress tended to increase as the bias voltages, while the adhesion strength reached the maximum value of 62.45 ± 2.65 N at −550 V. Under the synergistic effects of surface roughness, interfacial adhesion strength, hardness and elastic modulus, the average friction coefficient and wear rate of the coatings initially decreased and then increased, reaching the best tribological performance at −550 V. • PECVD was employed to deposit multilayer DLC coatings with a-Si:C:H bonding layer and H-DLC transition layer. • Bias voltages were adjusted to investigate the influences on the structure and properties of the DLC coatings. • DLC coating prepared at a bias voltage of -550V demonstrated the best tribological performance with a lowest wear rate. [ABSTRACT FROM AUTHOR]

The accumulated residual stress in yttria-stabilized zirconia top coat (YSZ TC) and thermally grown oxide (TGO) is regarded as the key driving force for the delamination of air-plasma-sprayed thermal barrier coating system (APS-TBCs). In this study, the synchronous evolution of residual stress of both YSZ TC and TGO, as well as the TGO thickness, are characterized via the Raman spectroscopy (RS) and photoluminescence piezo-spectroscopy (PLPS) methods. For the APS-TBCs where one surface is coated with YSZ TC, while the other surface remains directly exposed to high temperature, the service life can be categorized into four distinct stages: the early stage with tensile stress state (0–40 h), the medium stage with reversal compressive stress state (40–100 h), the late stage with re-inverted tensile stress (100–140 h), and the final stage with compressive stress state (140–300 h). Such stress reversal phenomenon may be attributed to the competition between the growth of TGO and substrate oxide (SO). It is advisable to apply an oxidation-resistant coating on the inner wall of high-temperature blade cooling passages, to prevent the formation of SO and consequently avoid complex stress transitions during high-temperature service of the APS-TBC, ultimately preventing local stress concentration-induced cracking and delamination. [Display omitted] • The synchronous evolution of the residual stress of both TGO and YSZ TC, as well as the thickness of TGO and pure α-Al 2 O 3 , in APS-TBCs is characterized. • A stress reversal phenomenon has been observed in APS-TBCs sample where one surface is coated with YSZ TC, while the other surface remains directly exposed to high temperature during oxidation services. • It is advisable to apply an oxidation-resistant coating on the inner wall of high-temperature blade, to prevent the formation of substrate oxide and ultimately preventing local stress concentration-induced cracking and delamination. [ABSTRACT FROM AUTHOR]

The effects of heat treatment on the microstructure, residual stresses, nano-indentation behavior, the resistance to the corrosion and cavitation erosion (CE) of 17-4PH stainless steel (17-4PH SS) by laser surface melting (LSM) were thoroughly investigated. Experimental results showed that the samples were mainly composed of martensite phase, and the NbC precipitations formed after heat treatment. The distribution of NbC precipitations was more uniform in the sample (S3) after solution treatment 3 h at 1040 °C + aging treatment 3 h at 480 °C. The grain size was increased for the samples after heat treatment. This heat treatment processing significantly reduced the residual stresses generated from the LSM process, and the nano-indentation behavior of the LSM samples after heat treatment was improved compared to that of the LSM sample without heat treatment. The S3 sample displayed the highest corrosion resistance as indicated by the low corrosion current density (i corr), high pitting potential (E pit) and high polarization resistance (R p). The CE resistance of samples after heat treatment in 3.5 wt% NaCl solution was higher than that of the sample without heat treatment. Among them, the S3 sample exhibited the highest CE resistance, and its CE mass loss was only 59.5 % of the sample without heat treatment. The excellent CE resistance resulted from the appropriate combination of mechanical properties, corrosion resistance and self-recovery ability of the passivation film. • 17-4PH stainless steel by laser surface melting was subjected to heat treatment. • The microstructure and residual stress of samples after heat treatment were studied. • The nano-indentation behaviors of samples after heat treatment were improved. • The resistance to corrosion and cavitation erosion was improved. [ABSTRACT FROM AUTHOR]

Residual stress in multilayer coatings is a complex phenomenon influenced by layer number and thickness, layer and substrate materials, deposition technique, process parameters, and working pressure. It is crucial to realize these stresses because they have a significant impact on the performance and reliability of multilayer structures in their applications. The measurement of the residual stress on multilayer thin films locally and globally is crucial. This study employed ring-core milling residual stress measurement on the High-Power Impulse Magnetron Sputtering (HiPIMS) fabricated Tungsten/Copper (W/Cu) Chromium/Copper (Cr/Cu) multilayer thin films. The displacement transformation strain was analyzed using Focused Ion Beam (FIB) ring-core milling combined with Digital Image Correlation (DIC), and the strain stress transformation calibration coefficients were analyzed through Finite Element Method (FEM) to investigate the residual stress of the thin films layer by layer. The study results indicated that the hard thin films (W, Cr) were the main source of residual stress in the multilayer thin film structure, while the soft thin film (Cu) had a lower residual stress. Having Cu as the intermediate layer was found to be effective for controlling the residual stress of thin films. The hard thin films encapsulated by the soft thin films had smaller stress values than those with hard films on the surface. In addition, the study observes the stress gradient and distribution at different depths and locations on the sample to reveal process parameters to balance between the soft and hard thin films and could help to predict the location of the damage on the multilayer thin films caused by higher stress. [Display omitted] • Fabricated W/Cu and Cr/Cu multilayer thin films using a High Power Impulse Magnetron Sputtering (HiPIMS) system. • Utilized an incremental FIB milling, DIC method and FEM coefficient parameters simulations for the residual stress measurement in W/Cu and Cr/Cu multilayer films. • Relaxation strain and stress calculation after Focused Ion Beam milling of W/Cu and Cr/Cu multilayer thin films. • Understand the role of Cu within W and Cr multilayer layer thin films for their residual stress behavior. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP), as a post-treatment process, was employed to improve the corrosion resistance of Ti45Al8Nb alloy fabricated via laser melting deposition (LMD). Microstructure analysis indicated that nanograins and nanotwins structures were formed on the surface layer of LSP-treated Ti45Al8Nb alloy, accompanied by high-density dislocations and stacking faults. Electrochemical results showed that LSP improves the corrosion resistance of Ti45Al8Nb alloy. The formation of nanograins, nanotwins and compressive residual stress during LSP was conductive to dense oxidation films, thus improving the corrosion resistance of the as-deposited Ti45Al8Nb alloy. • LSP improves the corrosion resistance of additively manufactured TiAl alloy. • Nanograins and nanotwins structures are formed through LSP, accompanied by high-density dislocations and stacking faults. • The grain refinement and compressive residual stress during LSP enhance the corrosion resistance. [ABSTRACT FROM AUTHOR]

NiCrAlY coatings are widely applied bond coatings in thermal barrier coating systems to prevent high-temperature oxidation of turbine blades. However, the uncontrollable microstructure design and high surface roughness seriously affect the oxidation resistance. Herein, NiCrAlY coatings fabricated through arc ion plating were subjected to high-repetition-rate femtosecond laser remelting (HRR-FLR) treatment. This study assessed the surface rumpling behavior, residual stress evolution, and thermally grown oxide (TGO) layer growth under thermal cyclic oxidation at 1100 °C to determine their impact on coating lifetime. The results indicated that the HRR-FLR treatment was effective in reducing surface roughness, restructuring microstructures, and redistributing reactive elements. These improvements facilitated the formation of a flat, continuous, and dense alumina layer, enhancing the spallation and rumpling resistance of TGO. Consequently, the efficiency of HRR-FLR technique was proven in significantly improving the lifetime of NiCrAlY coatings, which provides a new application prospect of femtosecond lasers in remelting and polishing of metallic surfaces. • NiCrAlY coatings prepared via AIP method were treated via HRR-FLR technique. • Microstructural modification and reactive elemental redistribution were obtained. • The surface rumpling behavior and residual stress evolution of TGO was analyzed. • The dense remelted layer facilitated the resistance of TGO to spallation and rumpling. • HRR-FLR technique is an effective method to improve the service life of NiCrAlY coatings. [ABSTRACT FROM AUTHOR]

It has recently been proposed to modify conventional WC-Co coatings with nano-sized particles to improve their properties. Modification of the coatings with nano-sized carbides may provide higher wear resistance or phase composition stability. This work characterized the changes in the residual stresses induced by introducing WC nanoparticles into a WC-Co coating and the resulting change in their sliding wear behavior. A powder mixture consisting of agglomerated and sintered WC-17Co feedstock powder and 5 % nano-sized WC was deposited on a carbon steel substrate using the High Velocity Air Fuel (HVAF) process. Microstructural characterization using scanning electron microscopy and EBSD confirmed that nano-sized WC particles were embedded in the coatings after the spraying process, primarily along the boundaries of the WC-Co lamellae. This resulted in an enhancement of microhardness, indentation fracture toughness, and dry sliding wear resistance, evaluated via ball-on-disk tests against Al 2 O 3 counterparts. Residual stresses in the coatings were also measured by XRD using the sin2ψ method. The normal stress along the torch movement direction decreased significantly when nano-sized WC was added. The addition of nanoparticles also caused a slight decrease in the normal stress perpendicular to the torch movement. [Display omitted] Nano-WC was embedded along splat boundaries in the WC-Co coating. Nano-sized WC addition decreases the normal stress along the torch movement direction. The nanoparticles compensate the WC loss due to decarburization along splat boundaries. Thus, the nanoparticles-containing coating has higher hardness and wear resistance. [ABSTRACT FROM AUTHOR]

In contrast to the conventional progressive scratch testing where load is increased up to a critical damage level, the repetitive scratch testing is an assessment of coating behavior under repeatedly applied subcritical load. It often represents a better approximation to actual application conditions of well-designed coating systems where overcritical conditions typically do not occur. In this work, the cyclic micro scratch behavior of differently doped amorphous carbon coatings with similar coating thicknesses were studied using repetitive scratch tests at loads that correspond to 40 %, 60 % and 80 % of the critical loads from progressive scratch testing. Depending on the doping element, the structural and mechanical properties changed, in some cases considerably, which also had a clear effect on the test results. The damage progression was examined using optical microscopy, friction coefficient, and residual depth measurements. The progression of failure phenomena was categorized into different stages. Furthermore, the critical number of cycles for coating failure was recorded at the various load levels. For the identification of the critical cycles, the use of the deviation of the friction coefficient from its mean value has proven to be a valuable parameter. The approach of testing at different load levels allows the creation of low cycle fatigue curves to evaluate the coating behavior. It was found that the hardness and residual stresses of the coatings had different effects on the lifetime of the coatings at the various load levels, i.e. higher hardness and residual compressive stresses were only beneficial for moderate stress levels with low plastic substrate deformation. The results demonstrate that the cyclic scratch test is a powerful tool for comparative damage assessment at different load scenarios. • Low cycle fatigue of ta-C and ta-C:X coatings investigated by repetitive micro scratch tests. • Subcritical load levels of 40 %, 60 % and 80 % of Lcs were used. • Progression of abrasive wear is described depending on the coating properties. • Number of cycles to failure determined from friction coefficient. • Different behavior of hard and soft coatings depends on subcritical stress level and residual stresses. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films were prepared on acrylate rubber (ACM) by varying the substrate bias voltage with bias gradient deltas of 25 V, 50 V, and 100 V during magnetron sputtering. The microstructure, mechanical and tribological properties of DLC films on ACM substrate were systematically investigated by SEM, AFM, Raman and XPS et.al in detail. The results show that the DLC film with a bias gradient delta of 25 V exhibited the most sp3 content and with the decrease of bias voltage gradient delta, the sp3 content in DLC films shows an increasing trend. The ratio of H/E increases as the bias gradient delta decreases. The results of friction tests indicated that the wear resistance of DLC films is influenced by their bias gradient deltas, surface roughness, residual stress, adhesive strength, and the ratio of H/E&H3/E2. Furthermore, decreasing the bias gradient delta resulted in a reduction in wear volume. Among the tested films, the DLC film with a bias gradient delta of 25 V exhibited the lowest CoF of 0.14 and the least wear volume of 0.98 mg, respectively. These findings suggest that the said film prepared on ACM displays excellent wear resistance. [Display omitted] • The authors successfully prepared gradient DLC films with hardness from soft to hard at a thin film thickness. • The authors found that the multi-bias gradient DLC film relieves internal stress and enhances the adhesion strength. • The authors elucidated the mechanism by which multilayer DLC films mitigate wear through interfacial hindrance. [ABSTRACT FROM AUTHOR]

Two sets of nanoscale multilayer Ti-DLC/DLC coatings, with similar chemical composition but different periods between consecutive layers (0.4 and 5.5 nm), were deposited by non-reactive direct current magnetron sputtering using different rotational speeds of the substrate holder (12 and 1 rpm, respectively) in this work. The results show that the overall Ti content in the coatings varied from ≈ 2.9 to ≈ 8.2 at. % in both cases. Significant fluctuations in the Ti concentration between the middle points of the DLC and Ti-DLC layers were observed for the coatings deposited at 1 rpm. All the coatings deposited were mainly amorphous, presenting a columnar structure and a cauliflower-like granular surface morphology. The sp2/sp3 ratio increased as the concentration of Ti rose. The coatings deposited at 1 rpm demonstrated better mechanical properties (up to 33 % improvement in hardness and up to 25 % improvement in the elastic modulus) when compared to the equivalent coatings deposited at 12 rpm. The multilayer titanium doped coating (deposited at 1 rpm) with 5.9 at. % Ti presented the most significant improvement in mechanical properties when compared to pure DLC and monolayer coatings deposited at 12 rpm. The results confirmed that it is possible to tune the performance of this type of coatings by depositing alternating layers of pure DLC and Ti-doped DLC. [Display omitted] • Monolayer and multilayer Ti-doped DLC coatings were successfully deposited by DC magnetron sputtering. • Multilayer structure was achieved by controlling substrate holder rotational speed. • All the Ti-doped DLC coatings had higher values of adhesion than pure DLC. • Multilayer Ti-DLC coatings showed higher hardness and elastic modulus than monolayer coatings. • The period of the layers, chemical composition, and residual stresses affected the performance of the coatings. [ABSTRACT FROM AUTHOR]

This work systematically studied the effects of stress shot peening (SSP) on the microstructure, residual stress and hardness of the ultrafine-grained Al 18 B 4 O 33 whisker reinforced Al-Mg-Si matrix composite (Al 18 B 4 O 33 w/Al-Mg-Si) by the modified Warren-Averbach method, X-ray diffraction stress equipment, transmission electron microscopy and hardness tester. The results showed that conventional shot peening generated a gradient deformation layer of the Al 18 B 4 O 33 w/Al-Mg-Si with ultrafine grains (200–400 nm) near the surface layer. By contrast with conventional SP, SSP effectively induced superior microstructures at the deformed zone with finer crystalline size and more dislocations. In parallel, SSP effectively enhanced the compressive residual stress (CRS) distribution with a higher magnitude of surface CRS (−83 MPa) and maximum CRS (−152 MPa) value and deeper affected depth along the loading direction. The fragmentized whisker during SSP acted as the pinning role on the dislocation movements, which was beneficial for grain refinement and CRS improvement. It is concluded that SSP technique can be regarded as an effective process of improving the surface properties of ultrafine-grained Al 18 B 4 O 33 w/Al composite. • A gradient ultrafine grained layer was developed by shot peening. • Stress shot peening induced smaller crystalline size, more dislocations and weaker texture. • Stress shot peening produced higher-level compressive residual stress and stiffer surface layer. • The fractured Al 18 B 4 O 33 whiskers during shot peening contribute to the improvement of surface characteristics. [ABSTRACT FROM AUTHOR]

Ni–Ti based shape memory alloys (SMAs) are popularly known for its biomedical applications due its excellent superelastic property. In order to modify the mechanical properties of the base Ni–Ti alloy, ternary alloying elements (e.g. Co) are generally added. The Co addition to Ni–Ti base alloy has helped in increasing the plateau stress of the hysteresis curve. Shot peening is one of the most widely used techniques to improve the fatigue life of SMAs by inducing compressive residual stress. It was believed that the shot peening has both equally affected the residual stress and texture of the alloy. And there are instances where certain texture orientation has played key role in improving the fatigue life of shape memory alloys. The main objective of this study is to understand the micro-texture evolution and residual stress generation supported by stress-induced phase transformation during shot peening process. The alteration of the shot-peened surface is assessed using X-Ray diffraction (XRD) and Electron Back Scatter Diffraction (EBSD) techniques. More compressive residual stress was induced in shot peened Ni–Ti (NT) alloys compared to Ni-Ti-Co (NTC) alloy due to more stress-induced phase transformation. The band like features generated during shot peening of Ni–Ti as was found to be missing in case of shot peened Ni-Ti-Co alloy. The incomplete phase transformation in shot peened Ni-Ti-Co alloys gave rise to coarser grain as compared to peened Ni–Ti alloy. The shot peening has resulted in preferred orientation of grains along the 〈111〉 direction that has helped in inducing maximum compressive residual stress. [Display omitted] • Shot peening of Ni–Ti and Ni-Ti-Co alloys in rod/cylindrical shape • Micro-texture/EBSD study of shot peened NiTi and NiTiCo alloys • Mathematical corrections to the measured residual stress values • Variation of residual stress from surface to core of shot peened alloys [ABSTRACT FROM AUTHOR]

Nb-based C103 is an increasingly relevant material for aerospace applications due to recent advances in additive manufacturing (AM). AM enabled complex component geometries, along with the associated surface roughness, are a challenge to the survival of environmental barrier coatings (EBCs), like R512E. EBCs are necessary to provide protection for the oxidation susceptible C103 substrates in elevated temperature, oxidizing environments. This work leveraged cyclic thermal exposures to understand the role of AM surface finish on the residual stress, the oxidation protection mechanisms, and the survivability of the R512E coated C103, with insight into the corner geometry-dependent performance supported by finite element modeling (FEM). The experimental characterization indicated that the rough surface finish from AM resulted in increased voids within the build layers in the diffusion formed coating, which in conjunction with tensile residual stress along the substrate interface, negated the coating protection during thermal cycling. Conversely, the coating applied to prepared surfaces indicated survivability throughout the exposures. Furthermore, the coating's experimental corner-dependent performance was consistent with the FEM results, highlighted by increased damage around sharp corners with improved coating performance at a fillet corner. These experimental and model results inform the surface and corner preparation requirements to leverage the benefits of AM in R512E coated C103 for elevated temperature applications. • Rough, L-DED C103 surface features caused increased damage in as-cured coating. • Spallation and coating protection negated due to AM substrate surface features. • Coating applied to substrates with prepared surfaces survived high heat flux torch. • Residual stress results revealed crack initiating stress and gradients at interface. • Modeled stress increase was consistent with local coating damage at sharp corners. [ABSTRACT FROM AUTHOR]

Several investigations on physical vapor deposition (PVD) coated steel substrates under cyclic bending load have reported an increase in fatigue strength of the coated compound. The compressive residual stress state of the coating can delay the initiation and propagation of surface or subsurface fatigue cracks. There are also investigations reporting no significant effect or a negative effect of PVD coatings on fatigue behavior of steels. The argument here is that the coating cracks during deformation and may lead to an earlier crack initiation in the substrate. Therefore, the effect of PVD coatings on fatigue behavior needs to be studied independently for different substrate materials. Here, the investigations on fatigue behavior of PVD coated tool steels are rather limited. Moreover, the fatigue damage mechanisms have been analyzed ex situ after the sample failure mostly for low stress amplitudes. The presented work is aimed at investigating the effect of CrAlN coating on the fatigue behavior of HS6–5-2C tool steel along with the analysis of fatigue cracks initiation and propagation in coated compound. For this purpose, the fatigue behavior of uncoated and coated tool steel was studied at high as well low bending stress amplitudes. Scanning electron microscopy (SEM) was used to analyze the fractured samples. Moreover, the fatigue damage mechanism in coated compound was studied in situ by carrying out a cyclic bending test inside large chamber SEM. It was shown that the fatigue damage in PVD coated high speed tool steel compounds under cyclic bending load is largely initiated in the substrate at low stress amplitudes. Here, the large carbide particles, carbide clusters or nonmetallic inclusions at the substrate surface or subsurface act as fatigue crack initiation sites. Depending on bending stress amplitude and residual stress state of the PVD coating, the coating may resist the propagation of fatigue cracks in certain cases to positively influence the fatigue behavior of tool steel substrate. The investigation contributes to fundamental understanding of fatigue damage in PVD coated tool steel compounds. • In situ observation of fatigue crack in large chamber SEM under cyclic bending load. • Fatigue damage in coated tool steel is largely substrate initiated at low stress amplitudes. • PVD coating may affect fatigue behavior of tool steel at low stress amplitudes. • Carbide particles or nonmetallic inclusions in substrate act as crack initiation sites. [ABSTRACT FROM AUTHOR]

Polycrystalline nickel-based superalloys are widely used in the aerospace industry. However, their prolonged exposure to extreme high and low temperature service environments frequently results in thermal fatigue cracks, adversely affecting their lifespan. Herein, a gradient reinforced layer is successfully fabricated on the nickel-based high-temperature alloy K403 using ultrasonic shot peening (USP). This treatment notably enhanced the surface hardness from 374 HV to 544 HV and increased the residual compressive stress from −117 MPa to −543 MPa. Thermal fatigue tests show that this reinforced layer effectively hinder surface oxidation and microstructural degradation, extending the initiation of thermal fatigue cracks from 50 to 100 cycles. Experimental observations and detailed microstructural evolution analysis reveal that USP creates a gradient structure of closely intermingled γ and γ′ phases on the surface, along with residual stress, which inhibits γ′ phase degradation, carbide precipitation, and diffusion during thermal fatigue cycles. These findings underscore the potential of USP as a surface treatment technique to markedly improve the thermal fatigue performance of high-temperature alloys. • USP extends crack initiation, enhancing resistance to thermal fatigue. • Alloy hardness post-USP increases from 374 HV to 544 HV, maintaining high residual stress for improved thermal stability. • USP raises microstrain and dislocation, forming shear bands and gradient structures for enhanced high-temperature stability. • USP creates a compressed surface structure, limiting atom migration and oxidation, thus improving thermal fatigue performance. [ABSTRACT FROM AUTHOR]

The interlayer design is crucial in optimizing the adhesion of TiSiCN thin films on tool steel. Thus, Ti/TiN/TiSiN interlayer systems were deposited varying the TiSiN interlayer bias voltages (−100 V, −150 V, −200 V) in a magnetron sputtering process to investigate the influence on the mechanical properties and adhesion of the TiSiCN top layer with different thicknesses. A higher bias voltage densifies the TiSiN interlayer structure, thereby increasing its residual stresses (0.11 GPa to 1.46 GPa) and hardness (28.1 GPa to 34.9 GPa). This occurs without affecting the columnar-like microstructure of the TiSiCN top layer and its hardness (25.9 GPa to 29.1 GPa for t = 1.0 μm, 22.6 GPa to 24.8 GPa for t = 2.3 μm). Adhesion classification by Rockwell C indentation of TiSiN declined from HF2 to HF4 due to increased residual stresses, impacting TiSiCN top layer adhesion with a similar deterioration. Scratch tests revealed reduced critical loads L c2 and L c3 for the TiSiN interlayer system and also for TiSiCN top layers. The highest critical loads were observed for TiSiCN (1.0 μm) and TiSiCN (2.3 μm) with TiSiN interlayer deposited at a bias voltage of −100 V, measuring (64.4 ± 4.5) N and (73.4 ± 8.3) N for L c2 , and (57.4 ± 5.3) N and (71.6 ± 4.5) N for L c3 , respectively. Increasing bias voltage decreases L c2 and L c3 to (23.2 ± 4.5) N and (50.20 ± 2.2) N for TiSiCN (1.0 μm), and (21.4 ± 4.5) N and (58.0 ± 3.6) N for TiSiCN (2.3 μm). Achieving high adhesion strength of TiSiCN multilayered system requires minimizing the residual stress differences between the layers. Therefore, when designing a complex multilayer structure for TiSiCN thin films, careful consideration of the stress state among the layers is crucial, which is achieved by adjusting the bias voltage. • Densification of TiSiN enhances its hardness with increasing bias voltage • Increased stresses within TiSiN reduce adhesion strength of TiSiCN • Higher mechanical mismatches between TiSiN/TiSiCN reduce adhesion strength [ABSTRACT FROM AUTHOR]

In this work, the effects of plasma nitriding, shot peening and their combination on the high-temperature wear resistance and stress corrosion resistance of an austenitic hot-stamping die steel were investigated. The results showed that the nitrided layer consisted of a single expanded austenite after nitriding at 560 °C for 4 h. Shot-peening pretreatment improved the surface hardness and depth of nitrided layer by 29.4 % and 36.4 % compared with the nitrided-only samples. This could be attributed to an increase in dislocation density, sub-crystal refinement, precipitation of nanoscale carbides and high strain of carbides and slip bands. Nitriding increased the stress corrosion resistance and high-temperature wear resistance of materials. Samples nitrided after shot peening showed the greatest wear and corrosion resistance. Besides, the introduction of residual compressive stresses in the nitrided layer by shot peening also improved wear and corrosion resistance to some extent. • Shot peening is applied before and after plasma nitriding. • Shot-peening pretreatment promotes the formation of nitrided layers. • Shot peening modifies dislocation density, subgrain size, carbide precipitation and strain field. • Nitriding after shot peening enhances wear and stress corrosion resistance. • Introducing compressive stresses into the nitrided layer improves wear and stress corrosion resistance. [ABSTRACT FROM AUTHOR]

HfN films with rocksalt structure have been grown by high-power impulse magnetron sputtering (HIPIMS) with various duty cycles, in a comparison with direct-current magnetron sputtering (dcMS) process. Such two sputtering processes yield the quite close compositions. Increasing the duty cycle from 7.5 % to 9 % and 11 % in HIPIMS process, a compressive stress rises up from 1.5 to 1.9 and 2.1 GPa, which is much smaller than the value of 3.8 GPa from dcMS. The hardness of such low-stressed HfN films has been identified to be 25.5–25.9 GPa, which agrees well with the theoretical one of 22.5 GPa by the density functional theory without the consideration of stress. In addition, the surface free energy of 26.3–29.0 mJ/m2 has been determined in HfN films grown by HIPIMS, much lower than that of 31.5 mJ/m2 of the films grown by dcMS. • Increasing the duty cycle from 7.5% to 11% in HIPIMS process, a compressive stress of HfN films rises up from 1.5 to 2.1 GPa. • The hardness of low-stressed HfN films grown by HIPIMS is about 26 GPa, agreeing well with the theoretical one of 22.5 GPa. • The surface free energy of HfN films grown by HIPIMS is much lower than that grown by dcMS. [ABSTRACT FROM AUTHOR]

Although the use of protective Ti(C,N)/Al 2 O 3 coatings produced by chemical vapour deposition (CVD) on cemented carbide (WC-Co) substrates is the state of the art in high-speed metal cutting, the effect of the substrate treatment on the microstructure of such coatings is not fully understood yet. In this study, the influence of the original substrate grain size (coarse-grained, fine-grained) and the substrate treatment (as-sintered, wet blasted, ground or polished) on the grain size, preferred orientation of crystallites and residual stress in Ti(C,N)/Al 2 O 3 coatings was systematically investigated. The microstructure analyses carried out using scanning electron microscopy with electron backscatter diffraction and symmetrical X-ray diffraction (XRD) revealed that the utilization of fine-grained substrates and the substrate treatment reduce the grain size in both layers, and increase the preferred orientations 〈211〉 and 〈0001〉 of fcc-Ti(C,N) and α-Al 2 O 3 crystallites, respectively. In α-Al 2 O 3 , the microstructure changes are mainly connected with the morphology of the bonding layer, as it follows the morphology of the fcc-Ti(C,N) facets. The residual stress analyses done using glancing angle X-ray diffraction (GAXRD) disclosed a reduction of the tensile thermal stress in α-Al 2 O 3 layers that were deposited on coarse-grained substrates. The residual stress in fcc-Ti(C,N) was substantially less reduced in the whole fcc-Ti(C,N)/α-Al 2 O 3 stacks than in the reference fcc-Ti(C,N) monolayers. Vice versa, fcc-Ti(C,N) in the full stacks contained less crystal structure defects and lower microstrain than in the reference fcc-Ti(C,N) monolayers, because they were exposed to higher temperatures. • Smooth substrates facilitate the growth of fine grained columnar fcc-Ti(C,N) grains with a strong 〈211〉 texture. • The roughness of the bonding layer is affected by the underlying Ti(C,N) facets. • Smooth substrates lead to straight surface of the bonding layer and to the formation of a strong 〈0001〉 texture in α-Al 2 O 3. • The relaxation of the tensile residual stress in Ti(C,N) is reduced in the Ti(C,N)/Al 2 O 3 /TiN coating stacks. [ABSTRACT FROM AUTHOR]

The influence of simultaneous dual Mo + Ru ion implantation into commercial TiN and TiAlN hard metal coated WC-10wt%Co-0.5wt%Cr 3 C 2 face milling inserts were investigated at dosages from 5 × 1015 to 1 × 1017 ions/cm2 at 100 keV acceleration voltage. Various characterisation techniques such as field emission scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, glancing incident X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterise the microstructure and topography of the as-received and ion implanted samples. The micro-hardness and residual stresses were also determined. Face milling tests were conducted to determine the effect of ion implantation on the wear rate. It has been observed that the dual Mo + Ru ion implantation with a biased Mo content extended 1000 nm into the dual TiN/TiAlN layer with significantly improved microhardness and increased anisotropy between the σ 11 and σ 22 stress components of the substrate, indicative of related effects in the coatings. The strengthening effect of Ru was observed at all ion implantation dosages even though wt% of Ru was significantly lower than the wt% of Mo. There were no visible changes to the microstructure of the substrate, but the presence of Mo and MoO 2 chemical phase contents were observed through XPS. All the ion implantation dosages improved machining performance as the wear rate of the ion implanted face milling inserts was lower than that of as-received TiN and TiAlN coated WC-10wt%Co-0.5wt%Cr 3 C 2 face milling inserts. • Ion implantation of Mo and Ru increases the surface micro-hardness of the TiN and TiAlN coatings in WC-10wt%Co-0.5wt%Cr 3 C 2 milling inserts. • Ion implantation dosage of 1 × 1017 ions/cm2 renders the highest micro-hardness increase. • Increased anisotropy was observed in the σ 11 and σ 22 , with σ 11 becoming more compressive and σ 22 less compressive with implantation dosages. • Ion implantation dosages from 5 × 1015 to 1 × 1017 ions/cm2 resulted in a reduced wear rate during the face milling test on an unhardened H13 tool steel. [ABSTRACT FROM AUTHOR]

A computational model has been developed to analyze calculations of residual stress in thin films determined from in-situ wafer curvature measurements. The model is based on several physical mechanisms that have been proposed to control the stress, including the effect of growth kinetics, grain growth and energetic particle bombardment. From a set of data, the program determines a set of kinetic parameters that can be used to understand the processes controlling stress. These parameters can be used to estimate the stress that will develop under different processing conditions in order to obtain a desired stress state. Several examples are described that illustrate the program's capabilities, including the effects of growth rate, growth temperature and particle energy (via chamber pressure in sputter deposition). Interested researchers may obtain the program and associated documentation to use the program to analyze their own data. • A computer model has been developed to analyze thin film stress determined from in-situ wafer curvature measurements. • The model includes effects of non-energetic growth kinetics, grain growth and energetic particle impacts. • Growth rate, temperature and pressure dependence is analyzed for evaporated, electrodeposited and sputtered films. [ABSTRACT FROM AUTHOR]

This study explored the corrosion resistance of 7075-T6 aluminum alloy by immersing it in a 3.5% NaCl solution to induce corrosion damage, and subsequently repairing the sample surface using ultrasonic nanocrystal surface modification (UNSM). UNSM was found to effectively repair the defects on the surface of the pre-corroded sample and improve its stress corrosion crack (SCC) resistance. The improvement in corrosion resistance and SCC resistance of sample was mainly due to the compressive residual stress and grain refinement caused by UNSM, which not only improved the pitting resistance but also effectively inhibited the initiation and extension of stress corrosion cracks. • UNSM refined the grains and increased the hardness of the surface layer. • UNSM introduced compressive residual stresses in the surface layer. • UNSM improved the corrosion resistance and SCC resistance of aluminum alloy. • UNSM can effectively repair corrosion damage of aluminum alloy. [ABSTRACT FROM AUTHOR]

Monolithic and multilayered W N and W–Si–N coatings were fabricated through direct current magnetron cosputtering at substrate holder rotation speeds of 0 and 5 rpm. The mechanical properties, structural evolutions, and oxidation behaviors of the W N and W–Si–N coatings were investigated through nanoindentation, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The mechanical properties of crystalline W N coatings correlated to their textures and residual stresses. The monolithic W 77 N 23 samples located closest to the W target exhibited a high deposition rate of 18.0 nm/min, a strong (200) texture coefficient, a high nanoindentation hardness of 32.7 GPa, a high Young's modulus of 392 GPa, and a high residual stress of −3.2 GPa. The addition of Si into the W N matrix transformed the monolithic W–Si–N coating into an X-ray amorphous phase dominated structure that comprised Si 3 N 4 , W 2 N, and W constituents. Ion bombardment caused the formation of multilayered W 78 N 22 samples with high residual stress and mechanical properties. The mechanical properties and residual stresses of the multilayered W–Si–N coatings decreased due to the preferential formation of Si 3 N 4. By contrast, oxidation resistance was improved by adding Si content higher than 24 at.% with annealing at 600 °C in a 1% O 2 –99% Ar atmosphere. • W N with a (200) texture exhibited high residual stress and mechanical properties. • X-ray amorphous W–Si–N coatings comprised Si 3 N 4 , W 2 N, and W constituents. • Mechanical properties of multilayered W–Si–N decrease with an increase in Si content. • SiO 2 scale provided the oxidation resistance for W–Si–N coatings. • Nitrogen loss caused improvement in the mechanical properties. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a solid-state additive material deposition technique, which has gained attention in the aerospace industry as a potentially viable technology for structural repair of high-value parts made of high-strength alloys such as Ti-6Al-4V (Ti-64). Residual stresses build up in the substrate and deposited materials resulting from the CS process can influence the integrity of a coating or repair. However, the nature, magnitude and distribution of residual stresses in Ti-64/Ti-64 CS repairs are currently unknown. This study aims to evaluate the effects of geometrical variables (i.e. the number of CS layers, CS layer thickness, and substrate thickness) and track pattern on the magnitude and distribution of residual stresses in CS deposit-substrate assemblies. Through-thickness stress distributions were measured experimentally by neutron diffraction and contour method. Furthermore, a comparison among different residual stress build-up mechanisms induced by CS processes has been discussed for different combinations of substrate and deposit assemblies. An analytical model based on the force and moment equilibrium requirements was used to interpret the experimental stress profiles and to predict the residual stress distribution. It was found that residual stresses are highly tensile near the free surface of the Ti-64 deposits as well as towards the bottom of the substrate, and compressive near the interface region. Although all the specimens showed similar stress distribution, the magnitudes were found to be higher in one or more of the following cases: specimens with a higher number of CS layers, lower substrate thickness, higher layer thickness (i.e. at lower scanning speed), and deposited with a horizontal track pattern. • Residual stresses induced by cold spraying of Ti-6Al-4 V were evaluated using neutron diffraction and contour method. • A parametric study was performed on the influence of geometrical and process variables on residual stresses. • An analytical method was used to interpret the experimental results and to compare different stress build-up mechanisms. [ABSTRACT FROM AUTHOR]

Over the last decade, great efforts have been undertaken in science and industry to provide WC-Co feedstock with nano-sized WC particles that significantly improves tribo-mechanical coating properties. For tribologically stressed surfaces, superior surface characteristics can be achieved by applying tailored surfaces, using novel technologies in the field of production engineering such as High-Feed Milling (HFM). For the first time, textured surface patterns were produced onto HVOF sprayed WC-Co coatings with nano-sized WC particles by implementing a HFM post process. In dependence to two different textures resulting from the HFM, the microstructural characteristics of the produced surfaces are analyzed. Confocal microscopy revealed the machinability of textured patterns onto a HVOF-sprayed WC-12Co hard coating, which comprise of nano-sized WC particles, by means of HFM technology. X-ray diffraction analyses confirmed the insertion of macro- and micro-scale residual stresses. The experiments showed a significant insertion of compressive residual stresses transverse to the feed direction, whereas the insertion of compresses residual stresses with its feed direction being less pronounced. It was found that the HFM post process leads to a refinement of the WC crystallite size and a distinct increase of its internal strain, which both can be attributed to plastic deformations during HFM. • HFM allows the feasibility of deterministic surface textures onto WC-Co coatings. • HFM leads to an insertion of compressive residual stresses with an anisotropic state. • In-plane stresses measured transverse to the milling direction possess higher values. • HFM leads to a refinement of the WC crystallite size and growth of its internal strain. [ABSTRACT FROM AUTHOR]

Multilayer tetrahedral amorphous carbon (ta-C) films comprising alternating layers of different sp3 contents have been fabricated by periodically adjusting the bias voltage of filtered cathodic vacuum arc (FCVA) system. The microstructure, tribological and corrosion behaviors of the multilayer ta-C films deposited on YG6 cemented carbide were systematically investigated. Results showed that the multilayer structure effectively reduced the residual stress and restrained spalling of ta-C film, which frequently occurred in single-layer structure. The hardness and Young's modulus of multilayer ta-C films decreased with diminishing sp3 content of soft sublayer. Compared to the YG6 substrate, multilayer ta-C films exhibited much lower friction coefficient between 0.06 and 0.08 and effectively reduced the wear rate. Multilayer ta-C film deposited at bias voltage alternating between −50 V and –150 V (M-1 film) had the lowest friction coefficient of 0.06 and the lowest wear rate of 2.87 × 10−7 mm3/N m. The difference in anti-wear performance among the multilayer ta-C films was associated with the ratio of hardness to elastic modulus (H/E ratio). The electrochemical corrosion test confirmed the effective corrosion protection provided by the multilayer ta-C films, and the M-1 film obtained the highest polarization resistance. Judging from electrochemical impedance tests, the existence of some extent of microdefects could be the main factor limiting the electrochemical corrosion performance of the multilayer ta-C films. Unlabelled Image • Multilayer ta-C films with controlled sp3 content were fabricated by FCVA system. • Tailoring the sp3 content between adjacent ta-C sub-layer reduced the residual stress. • Multilayer ta-C films exhibited improved tribological and corrosion properties compared to YG6 cemented carbide. • The H/E ratio was considered as an indicator of wear resistance. [ABSTRACT FROM AUTHOR]

In the present work, Ni-based plasma sprayed coating was prepared on the surface of AISI 1045 steel and subsequently remelted by induction heating method. On base of this, the rolling/sliding contact fatigue behaviors of the two coatings under different contact stress were studied. The results indicated that, the induction remelting improved the microstructure and microhardness of the coating, and changed the bonding form between the coating and the substrate from mechanical bonding to metallurgical one. The rolling/sliding contact fatigue performance of the sprayed coating was very poor and interfacial delamination was the only failure mode. However, that of the remelted coating was remarkably superior to the sprayed coating. Moreover, with the increase of contact stress, the fatigue life of the remelted coating decreased, but its Weibull distribution of fatigue life became more concentrated. The main failure modes of the remelted coating under different contact stress were pitting and spalling. The failure mechanism of the sprayed coating was that the weak interface bonding and the combined action of residual stress and shear stress resulted in the interfacial delamination. For the remelted coating, pitting was attribute to the combined action of contact stress and high-pressure oil wave, while the spalling resulted from the synergistic action of the residual stress and shear stress. • Rolling/sliding contact fatigue of sprayed and remelted coating were investigated. • Residual stress can affect the contact fatigue performance of the coatings. • Fatigue life of the coating can be dramatically improved by induction remelting. [ABSTRACT FROM AUTHOR]

Aluminum-Copper alloys are widely utilized in military, aerospace and aircraft industries for its light weight, excellent castability, superior corrosion resistance, as well as high specific strength after solution, quenching and age hardening treatments. However, the distortion occurring in the quenching process limits its application, especially for the large scale complicated workpieces. In this study, a novel duplex treatment combining the coating and nitriding is applied to the sections of the thin-wall barrel that easy to deform during quenching. The results show that a gradient multiphase layer, consisting of two different regions, is shaped on the thin-wall sections easy to deform. The phase compositions of the surface and subsurface layer are dominated by TiN 0.3 and Al 3 Ti, respectively. The Young's modulus of the TiN 0.3 and Al 3 Ti are 199 GPa and 196 GPa respectively. While, the microhardness for both the two phases are 6.19 GPa and 4.24 GPa respectively, which are much higher than that for the aged ZL205A alloy substrate. The finite element method (FEM) simulation results show that the maximum temperature difference, thermal stress, residual stress as well as deformation of the thin-wall barrel workpiece are reduced due to the multiphase layer. Consequently, the maximum radial deformation of the workpiece can be reduced 96% due to the superior strength and hardness as well as heat conduction of the gradient multiphase layer. • Quenching deformation occurs on the thin-wall sections of the barrel according to the FEM simulation. • The gradient multiphase layer is prepared on the thin-wall sections by deposition titanium film and nitriding. • The phase composition of the multiphase layer is dominated by TiN 0.3 and Al 3 Ti. • The much higher heat conductivity and superior strength and hardness of the multiphase layer results in 96% reduction of the workpiece. [ABSTRACT FROM AUTHOR]

The residual stress and distortion caused by non-uniform temperature distribution has limited the application of cold spray (CS) technique as an effective additive manufacturing and damage repair method for large-scale components. In order to investigate the influence of heat accumulation on coating quality, two types of CS Ni coatings with different building dimensions were deposited onto substrates. The type II Ni coatings with smaller fabrication size possess a fully dense microstructure without cracks, while the type I coatings with larger size show a significantly higher porosity value. The type II coatings show relatively higher microhardness. The tribological tests show that the type II Ni coatings present a better wear resistance with lower coefficient of friction and lower wear rate. The distinct worn morphologies show that the lower microhardness and porous microstructure of type I coatings lead to numerous delamination and exposure of interior coating. According to the temperature history recorded by infrared imaging camera, higher average temperature was found at the type II coatings due to enhanced heat accumulation of coating/substrate system at the short nozzle movement. The increased particle plastic deformation can further promote the coating densification rate and further ameliorate the coating quality. It can be summarized that the nozzle trajectory and deposition strategy can affect the temperature distribution and determine the coating qualities. This work provides a potential guidance for the optimization of coating quality by cold spraying additive manufacturing. • Effect of heat accumulation on coating properties in cold spray is studied. • Ni coatings with distinct building dimensions were deposited on substrates. • Ni coatings with smaller size possess lower porosity and better wear resistance. • The higher temperature at smaller building dimension brings better coating quality. [ABSTRACT FROM AUTHOR]

Residual stress is an important factor that may influence the integrity of plasma sprayed coatings, as well as the performance and lifetime of coated parts. The stress, in turn, is influenced by the properties of the substrate and coating materials and by the processing conditions. Moreover, specific stress-strain behavior of plasma sprayed coatings stems from their characteristic structure, which is again influenced by the spraying parameters. In this work, the curvature and temperature monitoring by "ICP" (In-situ Coating Properties) sensor was used to track the stress evolution during and after coating deposition and to determine the coating stiffness; this was complemented by 4-point bending, hardness measurement, microstructural observations and image analysis. Representative ceramic, metallic and composite coatings, including functionally graded materials (FGMs), were investigated. The effects of processing parameters, such as deposition temperature, particle temperature and velocity, deposition rate and coating/substrate material combination were demonstrated. Ceramic Al 2 O 3 coatings exhibited residual stress values in tens of MPa and extensive splat cracking; their moduli were higher when loaded in compression than in tension. Metallic coatings (Cu, W, and W + Cu composites) showed residual stress values in hundreds of MPa without significant cracking. Residual stresses as well as coating moduli were higher for mixed W + Cu composites than for 100% W or 100% Cu coatings, possibly as a result of stronger intersplat bonding across heterogeneous interfaces. It was also shown that residual stress profiles in W + Cu FGMs may be significantly altered by intentional design of the gradation profile and that experimental data evaluated by ICP during the actual deposition of the FGM coating were in good agreement with theoretical model based on data from the deposition of individual mixed W + Cu layers. Higher stress and modulus magnitudes were generally observed under conditions resulting in stronger bonding between the splats. • The ICP sensor was for the first time applied in the harsh environment of high- enthalpy WSP plasma spraying • Materials and processing effects on stresses, mech. properties and microstructure were studied for Al2O3, Cu and W+Cu • Specific trends in mechanical properties were identified and linked to process parameters through microstructural characterization [ABSTRACT FROM AUTHOR]

An experimental study is performed to assess the surface integrity of cold sprayed and laser cladded 17-4PH stainless steel deposits after turning and ball-burnishing. A special emphasis is given to near surface microstructure and residual stress distribution. It is shown that both cold spray and cladding deposits could be machined under cutting conditions close to those employed for a conventionally rolled 17-4PH stainless steel. Analysing the resulting microstructure in the near-surface revealed that the turning and ball-burnishing processes affect the coating surface and generate a thin layer where the microstructure can be hardly identified. Residual stress measurements by an X-ray diffraction method revealed that turning results in tensile residual stresses in the near-surface of both the cold spray and laser cladding deposits. Surface treatment by ball-burnishing can be significantly beneficial as compressive residual stresses were measured in both coatings in the near-surface zone but to a larger extent in the cladded material. The comparison of the two profiles showed that the cutting and deformation mechanisms can be significantly different depending on the intrinsic nature of the deposited microstructure. • 17-4PH thick coatings are produced by cold spray and laser cladding. • The influence of turning and ball burnishing on these coatings is investigated. • Both microstructures exhibit a thin transformed layer close to the near surface after applying both processes. • Tensile residual stresses are generated at the extreme surface of both coatings after turning. • Ball-burnishing can induce compressive stresses but to a different extent depending on the deposition process. [ABSTRACT FROM AUTHOR]