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Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the effects of surface treatment namely electro-pulsing followed by laser shock peening (EP-LSP) on wear resistance properties of Ti–6Al–4V alloy are investigated. It was compared with samples treated solely with laser shock peening (LSP) and electro-pulsing treatment (EP) to investigate the effects of different processes on the friction and wear properties of Ti–6Al–4V alloy. In addition, the friction coefficient, wear rate, wear morphology were also investigated. Finally, the wear mechanism was described in detail. The results demonstrated a significant reduction in grain size for the samples after EP-1-LSP treatments. Furthermore, compared with the as-received samples, the maximum hardness of EP-1, LSP and EP-1-LSP treated samples increased by 6.5%, 5.9%, and 19.6%, respectively, and the compressive residual stress on the surface increased by 2.4%, 15.0%, and 37.2%, respectively. Under the same friction conditions, the depth of wear scar of the samples after EP-1, LSP, and EP-1-LSP treatments decreased by 7.2%, 10.6%, and 18.5% than that of the as-received sample. The as-received samples mainly exhibited severe oxidative and adhesive wear, and the LSP and EP-1 treated samples showed slight adhesive and oxidative wear. The EP-1-LSP treated samples predominantly showed signs of abrasive wear.

In this paper, we designed the A356-B2O3-KBF4 reaction system to synthesize (AlB2 + Al2O3)/A356 biphasic particles-reinforced aluminum matrix composite with varying weight percentages (2%, 4%, 6%, and 8%). The synthesis was achieved through mechanical mixing and mixed salt reaction. We studied the friction and wear performance of the composite at room temperature using XRD, PC, SEM, EDS, laser confocal microscopy, and microhardness analysis. Our results indicate that the AlB2 and Al2O3 duplex-enhanced particles were effectively synthesized, with predominantly short rod morphology and local clustering observed for the AlB2 particles. The AlB2 particles were mostly in the micron-scale range, while the Al2O3 particles were mostly in the nanoscale range, both exhibiting agglomeration phenomena. Both enhanced particles showed an agglomeration phenomenon and could grow together with the interface binding very closely. At 6 wt.% mass fraction of biphasic particles, the composite exhibited the best refinement effect on-Al grains, as well as the greatest friction reduction effect and wear resistance for both the (AlB2 + Al2O3)/A356 composite and the A356 matrix alloy. The wear mechanism was primarily abrasive wear, while the A356 matrix alloy's wear mechanism was adhesive wear. [ABSTRACT FROM AUTHOR]

In this paper, the A356-B2O3-KBF4 system was designed, and (AlB2 + Al2O3)/A356 in situ dual-phase reinforced particle composites with mass fractions of 2 wt%, 4 wt%, 6 wt% and 8 wt% were prepared by the DMR method. The acoustic-magnetic coupling control was carried out during the preparation of 6 wt% (AlB2 + Al2O3)/A356 composite. XRD, PC, SEM, EDS, and dry friction tests studied the composites' microstructure and high-temperature wear properties. The results show that the matrix α-Al grains of the composite are refined under the action of the coupling field, with a grain size of: 94.3 um. The AlB2 particles are rod-shaped with a radial size of 11 um, and the Al2O3 particles are nano-sized flakes. The wear mechanism of (AlB2 + Al2O3)/A356 dual-phase in situ aluminum matrix composites is high-temperature oxidation abrasive wear, which differs from the adhesive wear of the matrix alloy. Due to the anti-friction, lubrication and anti-wear effects of the dual-phase in situ particles (AlB2 + Al2O3), the wear resistance of the composites is improved, and the coefficient of friction is reduced by 13.4% compared to the A356 matrix alloy. With the increase in temperature, the wear resistance of 6 wt% (AlB2 + Al2O3)/A356-1 kW-10 Hz composite was substantially better than that of the A356 matrix alloy. The wear rate of the composite at different temperatures was reduced by 8.82% (100 °C), 11.29% (200 °C), and 13.69% (300 °C), respectively, compared with that of the matrix A356. [ABSTRACT FROM AUTHOR]

In this paper, preforms with three-dimensional structures and different thicknesses were constructed by 3D printing technology, and WC particle reinforced high-chromium cast iron (HCCI) composites was prepared by infiltration casting method. The microstructure of the WC/Fe matrix composites was investigated using scanning electron microscopy (SEM), energy spectroscopy (EDS), X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The effects of different preform wall thickness on the hardness and three-body abrasive wear properties of the composites were tested. The results showed that with the increase in the wall thickness of the three-dimensional preform from 2.5 to 10 mm, the volume of the composite zone formed by the dissolution diffusion reaction of WC and HCCI gradually increased from 31.8 to 41.2%. The microstructure was composed of composite zone, matrix and WC particles partially dissolved. The hardness of the composite zone increased at first and then decreased, while the wear weight loss of the composite showed an opposite trend. Compared with the wall thickness of 2.5 mm, the minimum wear weight loss of the composite was 0.2821 g for a wall thickness of 7.5 mm, and the wear resistance was improved by 12.8%. The hardness and wear resistance of WC/Fe matrix composites at different wall thicknesses were mainly related to the diffusion of the preform and the formation of the composite zone. [ABSTRACT FROM AUTHOR]

Double-layer Ni-P coatings with low phosphorus content in the inner layer and high phosphorus content in the outer layer and Ni-Mo-P composite coatings are successfully prepared on the surface of AZ91D magnesium alloy by chemical plating process. The microstructures, friction and corrosion resistance of double-layer Ni-P and Ni-Mo-P coatings are studied in comparison. Meanwhile, the deposition and corrosion resistance mechanism for the coatings are investigated. Results convey that both Ni-P and Ni-Mo-P coatings showcase an amorphous structure. The coating possesses denser and more homogeneous structure with the co-doping of Mo. The micro-indentation hardness (859.7 HV) and friction coefficient (0.58) of Ni-Mo-P coatings show that the ternary alloy coating is firmly bonded to the magnesium alloy substrate. Besides, the Ni-Mo-P coatings demonstrate exceptional wear resistance attributed to Mo co-deposition, fostering grain refinement and facilitating the growth of passivation films.

The silicon carbide (SiC) ceramic material was prepared by powder metallurgy processing route using spark plasma sintering (SPS) technique without any sintering additives. The effects of the SiC surface ablation by fiber laser and subsequent superficial incorporation of graphene nanoplatelets (GNPs) into the created microcraters were investigated in terms of their influence on the resulting tribological (i.e., friction and wear) behavior of the created SiC-graphene composite surfaces. It was clearly shown that the used laser treatment with the pulse duration in ms range led to desirable surface morphological changes, i.e., the creation of SiC ablated microrelief, suitable for GNPs incorporation. The friction and wear behavior of produced SiC-graphene composite surfaces was studied using translational ball-on-disc nanotribometer at room temperature and applied loading up to 1000 mN. The results showed that at all normal loads the wear rates of laser ablated surface materials were gradually decreasing as a result of frictional coefficient reduction. The observations of wear track topography indicated abrasive wear to be the dominant wear mechanism of the sintered SiC material. However, by incorporation of GNPs, the abrasive wear was significantly reduced by the graphene friction film created on the ablated SiC-graphene composite surfaces. [ABSTRACT FROM AUTHOR]

A kind of wear‐resistant diamond‐like carbon (DLC) films doped with Ni, N, and multiwalled carbon nanotubes (MWCNTs) are synthesized on Ti–6Al–4V titanium alloy by a combined method of pulsed electrodeposition and liquid‐phase electrodeposition. The effect of different concentrations of MWCNTs on the microstructure and friction mechanism of Co‐DLC films is investigated. The results show that the polydimethyl diallyl ammonium chloride (PDDA)‐MWCNTs complex tend to deposit parallel to the substrate. Benefiting from the "bridging" effect of the MWCNTs between the cluster structures, it effectively reduces the protrusions on the surface of the films. When the concentration of MWCNTs is 0.06 g L−1, the surface microstructure of the films is uniform and dense, and the films present a low ID/IG value (0.57) and a high sp3‐C content. The Raman and X‐ray photoelectron spectroscopy patterns reveal that the Ni/N/MWCNTs‐DLC films are typical amorphous carbon films. Furthermore, the micro‐indentation hardness of the Co‐DLC films reaches 513.24 HV. The lubricated Ni/N/MWCNTs‐DLC films significantly improve the frictional wear properties of the titanium alloy surface, which is mainly attributed to the homogeneous and dense structure and the low friction coefficient (0.146) and wear loss (1.40 × 10−5 kg m−1). [ABSTRACT FROM AUTHOR]

Lattice structures with graded composition and microstructure in function of position allow for a smooth transition and due to their combination of multiple desirable features show great prospects in various applications. This study describes the characteristics of Ni alloy-bronze composite lattice structures (CLS) which can be used for manufacturing slide bearings intended for operation under heavy loads. The CLS were fabricated via directed energy deposition method on a substrate of AISI 1045 structural steel. The basic microstructural characteristics as well as microhardness were analyzed to study the features of composite structures depending on the speed of the laser beam as well as the laser spot step. Operational tests of the studied CLS were carried out under different loads and lubrication conditions. It was confirmed that the CLS wear resistance is 5–12 times higher under dry friction conditions and ∼65 times higher under mixed lubrication conditions as compared to the initial Ni alloy and bronze. It was claimed that CLS tested and formed using modern directed energy deposition technology exhibit improved material and tribological characteristics. These results are important both from the standpoint of practical applications and future research.

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the Cr/Cr-W/W-DLC/DLC multilayer coating was deposited on 5A06 Al alloy using a combination of unbalanced magnetron sputtering system and filter cathode vacuum arc technique. Dry linear reciprocating sliding wear tests were performed to evaluate the tribological properties of the deposited coating at different temperatures from −100 °C to 25 °C. The microstructure, mechanical properties and wear characteristics of the multilayer coating were also characterized by SEM, EDS, nanoindenter and nanoscratch tester, respectively. The results show that, compared with 0 °C and 25 °C, the tribological behavior of the multilayer DLC coating exhibits significant differences at low temperatures. The formation of the transfer layer and the graphitization caused by the flash temperature contribute to explain the excellent tribological performance of the coating at room temperature and 0 °C. The deterioration of the tribological properties of the multilayer coating at subzero temperatures is ascribed to the inhibition of the graphitization process, as well as the oxidation and capillary action of water molecules. Cyclic shear stress and low temperature lead to the formation of microcracks and surface spalling, which also increases the friction coefficient and wear rate of the multilayer DLC coating.

In this work, we proposed a data-driven approach combining machine learning (ML), experiments and molecular dynamic (MD) simulation to accelerate the composition design and exploration of wear behavior in Al–Cr–Co–Fe–Ni based high entropy alloys. A Cuckoo Search-Artificial Neural Network (CS-ANN) model was proposed to deal with small sample data and showed fairly strong learning ability and generalization capabilities. Elemental analysis revealed that the microhardness can be enhanced by adding Al or reducing the proportion of Fe and Ni. Then the Al1.1CrCoFe0.9Ni0.9 HEAs were designed and prepared for experimental verification. The microstructure, phase composition, hardness, and wear resistance properties of the alloy were further investigated. Al1.1CrCoFe0.9Ni0.9 HEAs were composed of BCC+B2 phases, exhibited a microhardness of 580.6 HV. The wear rate was measured as 6. 04 × 1 0 − 6 mm 3 /(Nm) by the reciprocating dry wear tests, the average COF was estimated as ∼ 0.5. The main wear mechanisms involved abrasive wear and oxidation wear. MD simulations are used to analyze the atomic evolution and deformation mechanism during the nano scratch process. The obtained information would help either facilitate developing novel HEAs or utilize the HEAs effectively to resist wear. [Display omitted] • A data-driven approach combining ML, experiments and MD is proposed to accelerate the composition design. • The designed Al1.1CrCoFe0.9Ni0.9 HEAs exhibit high hardness and good wear resistances. • The main wear mechanisms involved abrasive wear and oxidation wear. • MD simulations are used to analyze the microstructure and deformation mechanism during the nano scratch. [ABSTRACT FROM AUTHOR]

The electroless Ni–Mo–P/CNTs composite coatings were applied on AZ91D magnesium alloys, and the effects of CNTs concentration on the microstructure, micro-indentation hardness, wear and corrosion behaviors of the composite coatings were studied. Meanwhile, the mechanism of wear and corrosion resistance for coatings was investigated. The results suggested that the surface morphology of the composite coating fabricated at 0.4 g/L CNTs concentration was smooth and compact, and the maximum micro-indentation hardness and minimum friction coefficient were achieved as 1263.54 HV and 0.201, respectively. The worn surface morphologies showed that the carbon film formed by the optimal concentration of CNTs was covered on the coating surface, which acted as solid lubricant to enhance the abrasion resistance of the composite coating. Furthermore, the coating deposited with 0.4 g/L CNTs concentration had excellent corrosion resistance, which could be attributed to the fine and dense structure which prevented the intrusion of corrosive liquid. [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]

The low hardness and limited anti-wear of aluminum alloys pose obstacles to their stability and service life, especially in corrosive environments. Here, the amorphous CrAlN coating was first deposited on aluminum alloy by DC magnetron sputtering. The CrAlN coating with 30.2% nitrogen content was dense and prevented the intrusion of oxidation and corrosive fluids, thus greatly improving the anti-corrosion of the coating. The wear rate of the coated aluminum alloy in 3.5% NaCl solution decreased by three orders of magnitude. This work paves the way for constructing amorphous protective coatings on light alloys. [Display omitted] • The amorphous CrAlN coating was first deposited on Al alloy by DC magnetron sputtering. • The microstructure and properties of the amorphous CrAlN coating was dominated by the coating's nitrogen content. • The resulting coating presented a leading corrosion resistance as compared with reported literature. • The wear rate of the coating in 3.5% NaCl solution was three orders of magnitude lower than that of Al alloy. [ABSTRACT FROM AUTHOR]

The PTFE coatings with excellent corrosion-resistance and lubrication properties often stop functioning under high load conditions. In this study, a composite coating of PTFE filled with silane coupling agent modified graphene oxide (mGO/PTFE) was prepared by a simple spin-coating process on textured stainless steel (SS) substrate to protect the substrate from failure under high load rubbing. The grafting reaction between GO and silane coupling agent was analyzed by FTIR, Raman, XRD, TGA, and XPS. The morphologies and tribological properties of the mGO/PTFE coatings on the untextured and textured SS substrates were characterized by SEM and UMT tribometer. The results showed that GO surfaces were successfully grafted by silane coupling agent, resulting in that the composite coating of mGO/PTFE was denser than the pure PTFE coating. The tribo-test results confirmed that the groove texture processed by laser surface texture technology greatly improved the load-bearing capacity and anti-wear life of the PTFE coatings. The PTFE coating on the untextured SS surface fails within half an hour of rubbing at the applied load of 10 N, while the one on the groove-textured surface can maintain low and stable friction coefficient for a long time even under the load of 50 N. In addition, the results showed that the loading of mGO further improve the friction reduction and wear resistance of the PTFE coating on the textured SS surface. The wear scar width and the friction coefficient are significantly reduced by 70% and 30%, respectively, as the PTFE coating was filled by 1.0 wt% mGO. Finally, the mechanisms for achieving outstanding properties of the composite coating of mGO/PTFE on the textured SS surface were illustrated by analyzing the wear surfaces of the coating and the counterpart balls by SEM and EDS. [ABSTRACT FROM AUTHOR]

Diamond‐like carbon (DLC) possesses brilliant and excellent properties, including excellent corrosion resistance as well as outstanding wear resistance. Ni and B co‐doped DLC films were deposited on AZ91D magnesium alloy by electrodeposition under mild conditions (300 V and 25°C). Uniform and dense morphology of co‐doped DLC films were observed, and Ni and B were uniformly incorporated into the carbon‐based films. Among all the electrodeposits, the appearance of D and G peaks near 1330 and 1570 cm−1 revealed that the as‐deposited films were typical DLC films. As the addition of Ni was increased to 0.05 g, the highest microindentation hardness, the lowest friction coefficient, and wear loss were achieved to be 164.5 HV, 0.3, and 0.6 × 10−5 kg/m, respectively. The amorphous carbon films fabricated at 0.05 g Ni had the lowest corrosion current density and the most positive corrosion potential, which was mainly due to the small and dense granular structure effectively hindering the penetration of corrosion media. [ABSTRACT FROM AUTHOR]

Friction and wear performance is one of the key mechanical properties of accident tolerant fuel cladding coatings. In this study, reciprocating sliding wear tests had performed on two types of CrAl and CrAlN coatings with two different Al content ratios and Zr-4. The coefficient of friction, wear depth, and abrasion loss were measured and compared. The results indicated that the CrAl-based coatings improve the wear behavior significantly and nitrogen has an obvious improvement on the wear resistance of the coating. The friction and wear performance was also studied in a water environment. The results show that the presence of water degrade the wear performance of Zr-4 and CrAl coatings but ameliorates the friction and wear performance of CrAlN coatings. The feasibility of depositing ATF coating on conventional Zr-4 substrates to mitigate the influence of grid-to-rod fretting was demonstrated.

PTFE coatings were deposited on the Si 3 N 4 /TiC ceramic substrate by using spray technology. The surface and cross-section micrographs, adhesive force of coatings with substrate, surface roughness and micro-hardness of the coated ceramics were examined. The friction and wear behaviors of ceramic samples with and without coatings were investigated through carrying out dry sliding friction tests against WC/Co ball. The test results indicated that the coated ceramics exhibited rougher surface and lower micro-hardness, and the PTFE coatings can significantly reduce the surface friction and adhesive wear of ceramics. The friction performance of PTFE-coated sample was affected by applied load due to the lower surface hardness and shear strength of coatings, and the main wear failure mechanisms were abrasion wear, coating delamination and flaking. It can be considered that deposition of PTFE coatings is a promising approach to improve the friction and wear behavior of ceramic substrate. [ABSTRACT FROM AUTHOR]

Effect of equal channel angular pressing (ECAP) and subsequent annealing on the microstructure, mechanical properties and tribological behavior of grade A shipbuilding steel was investigated. Coarse-grained microstructure of initial sample is eliminated during the ECAP at 375 °C and more refined microstructure is achieved. Post-ECAP annealing at 575 °C results in some grain growth, and also the cementite lamellae in the pearlite colonies is broken and got spheroidised during the annealing treatment. ECAP increases strength and hardness of steel significantly while it decreases the ductility. On the other hand, post-ECAP annealing treatment brings about an increase in ductility and diminishes the hardness, as expected. Strain hardening capacity, ductility, hardness and oxidation rate were found to be the main factors affecting wear resistance of the grade A steel. It was found that high hardness and strength, good wear resistance with sufficiently high ductility can be achieved in the grade A steel by applying ECAP + annealing processes. [ABSTRACT FROM AUTHOR]

Copper‐graphite composites with different copper content are prepared by spark plasma sintering (SPS) at 900 °C using copper‐coated graphite powder and ordinary graphite powder as raw materials. Two groups of specimens are used for friction testing, including the original specimens and K2Cr2O7‐H2SO4‐etched specimens. The density, microstructure, Shore hardness, resistivity and friction and wear properties of the samples were investigated using the Archimedes drainage method, scanning electron microscopy, a hardness tester, a resistance tester, and a friction tester. The results showed that the relative density of the samples with different compositions reached about 90 %, and with an increase of copper content, the density and the relative density of the copper/graphite composites increased. As the copper content increased from 10 wt % to 50 wt %, the Shore hardness of the composites increased from 37 HSD to 59 HSD. Under dry‐friction conditions, with an increase of Cu wt %, the friction coefficients and wear rates of the original specimens showed a downward trend, while those of the chemically etched specimens first increased and then decreased. Under water‐friction conditions, both the original samples and chemically etched samples show very low friction coefficients, about 0.15 and 0.12, respectively, which are far lower than the friction coefficients (∼0.20) obtained under dry‐friction conditions. The wear rates of the original specimens decreased with an increase of copper content, while those of the chemically etched specimens increased first and then decrease. The electrical conductivities of the copper/graphite composites were slightly reduced by chemical etching, but the resistivity of the copper/graphite composites remained at a low level of 10−7 Ω⋅m for a copper content of 40–50 wt %. [ABSTRACT FROM AUTHOR]

Ni3Si and Ni/Ni3Si composites were prepared by mechanical alloying with Ni and Si powders as raw materials. The phase composition, microstructure and wear properties of the Ni3Si and Ni/Ni3Si composites were investigated. The results showed that the Ni (Si) solid solution, Ni74Si26 and Ni31Si12 intermediate phases were formed during ball milling process and then Ni3Si nanocrystalline powder was produced after 30 h of milling. Based on Miedema's semi-empirical theory, the formation free energies of different phases formed during mechanical alloying of 3Ni–Si mixed powders were calculated. The results showed that the ordered phase of Ni3Si is stable under equilibrium conditions and has the lowest formation enthalpy during ball milling. Compared with the monolithic Ni3Si, the Ni/Ni3Si composite has an excellent friction and wear resistance and comprehensive strength and toughness. With the increase of load, the friction coefficient of the composite decreases, the wear rate of the composite increases first and then decreases. When the load is 10 N, the friction coefficient and wear rate of the Ni/Ni3Si composite are 0.246 and 5.23 × 10–4 mm3/(Nm), respectively. The main wear mechanism of the material experiences a transition from adhesive wear to abrasive wear with the increase of load, and exhibits a significant tribo-oxidation wear under all loads. [ABSTRACT FROM AUTHOR]

A series of FeCrNiMnAl _x (x = 0, 0.3, 0.5, 0.8, 1.0 in molar ratio) high entropy alloys (HEAs) were prepared by the vacuum arc melting method. The effects of Al content on the microstructure, mechanical and wear properties were investigated. For FeCrNiMn alloy, the microstructure was main homogeneous structure with face-centered cubic (FCC) phase, whilst FeCrNiMnAl _0.3 produced a dendritic microstructure consisting of a mixture of FCC + BCC + B2 phases, and the mixture BCC + B2 dendritic interdendritic microstructure appeared when the molar ratio of Al is beyond 0.5. The hardness and yield stress of the HEAs are effectively improved with the increased Al amount but the ductility is lowered. In this case, FeCrNiMnAl alloy showed decreased yield stress due to the deteriorated ductility. Moreover, the friction coefficient decreases, and the wear resistance improved with the increased aluminum content. FeCrNiMnAl _0.8 HEAs have the best wear resistance due to the advantages of achieving a balance of strength and ductility.

Quantitative analyses on the coefficient of friction of common coating waxes are necessary and essential for designing systems for coating, conveying, packaging operations, transporting, and storing of papers and paperboards, while analyses on wear behavior can be helpful for predicting performance durability of the coating surface. In this study, we investigated the friction and wear behaviors of six waxes including four commercial waxes and two soybean oil‐based wax developed in our lab for bulk corrugated coating. The effect of normal load, sliding velocity, and environmental temperature was evaluated. The friction coefficient of different waxes varies with sliding conditions. Higher normal load, sliding velocity, and environmental temperature resulted in significantly greater wear loss. Crystalline morphology and crystallinity of waxes were affected by the environmental temperature, and they correlate to the variations in friction coefficient and wear loss of these materials. [ABSTRACT FROM AUTHOR]

In present work, the Fe/Ti-15wt.%Cu-based metal matrix composites with three different Fe/Ti weight percent ratios (i.e., 40/25, 25/40, 5/60) and constant additions of non-metallic additives (i.e., 5 wt.% graphite, 5 wt.% SiC, and 10 wt.% ZrO2) were investigated. An innovative and ecologically friendly approach for laboratory preparation of the experimental composite materials was based on the secondary utilization (recycling) of the waste Ti-chips (turnings) from conventional machining operations. The material mixtures for the fabrication of the studied composites were prepared by common powder metallurgy pre-operations followed by final material processing using spark plasma sintering (SPS). The microstructure of the SPS-fabricated composite materials consisted of sintered grain matrix with various amounts and distribution of Ti-chips. The friction and wear behavior of the composites was analyzed from performed tribological measurements employing "ball-on-disc" test method. The results showed that the coefficient of friction was mostly decreasing with increasing the sliding speed and the amount of Ti-chips in the composites. The lowest abrasion wear rate exhibited the composite with 40 wt.% of Ti-chips thanks to its optimal microstructure with appropriate hardness and beneficial wear mechanisms characteristics. [ABSTRACT FROM AUTHOR]

Carbon fabric (CF) was pretreated by air-plasma bombardment and then further modified by deposition of polydopamine on the surface of the pretreated CF. Epoxy resin composites reinforced by unmodified or surface-modified carbon fabric were fabricated. The friction and wear behaviors of the resulting composites were evaluated in a ring-on-block contact mode. The flexural strength and Rockwell hardness of the composites were also evaluated. The morphologies of the worn surfaces of the unmodified and modified composites were analyzed by scanning electron microscopy. The surface treatment increased the surface roughness and changed the surface topography of the CF, which contributed to enhancing the interfacial adhesion of the composites and thus improved the mechanical properties and tribo-performance. The friction and wear properties of both the unfilled and filled composites were highly dependent on the load and sliding velocity. Moreover, the results were supplemented with scanning electron micrographs to help understand the possible wear mechanisms. [ABSTRACT FROM AUTHOR]

In this work, AlCrON coatings with various oxygen contents were deposited by multi-arc-ion plating technology. The effects of oxygen content on the microstructure, mechanical properties, wear and cutting performance of AlCrON coatings were investigated. The result showed that the O contents in the AlCrON coatings increased from 0 to 8.8 wt.% by changing the O2/N2 flow ratios during the deposition process. The AlCrON coatings mainly included fcc-CrN and fcc-AlN phases, and the Al2O3 and Cr2O3 were also confirmed by the XPS results. Addition of oxygen improved the adhesion strength of AlCrON coatings. The AlCrON coating with 4.0 wt.% oxygen content showed the low surface roughness, low friction coefficient and the minimum wear rate. Cutting results also showed that addition of oxygen improved the service life of AlCrON coatings under various cutting conditions. The service life of AlCrON coatings increased firstly and then decreased with increasing oxygen contents, and the AlCrON coating with 4.0 wt.% oxygen content had the maximum cutting length under various cutting conditions, which might be due to the decrease of surface roughness, increase of adhesion strength and hardness. The wear mechanism involved in cutting process included abrasive wear, adhesive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

Nickel-aluminum bronzes (NAB) are widely used in different applications due to their high mechanical properties and operational characteristics. These properties can be further improved using different finishing processes. This paper's objective involves the wear and surface integrity characterization of CuAl7Ni6P bronze coatings formed firstly by plasma spraying and then by laser alloying with WC and Cr 3 C 2 carbides. The YLR-2000 fiber ytterbium laser was used for laser processing and the effect of process conditions, namely a laser spot speed (LSS) and a square of the laser spot (SLS)was studied under 500 N and 1000 N loads. It was revealed that processing parameters do not have a significant effect on microhardness and friction process factors, but have significant effect on carbide alloying results. Under load of 500 N wear rates have an advantage up to 5–6 times regardless of the processing parameters and the type of reinforcing particulates. Under load of 1000 N alloying advantage is very high: 15–20 times using Cr 3 C 2 , and even 30–50 times using WC compared with results obtained for plasma spraying. These results are very important when choosing NAB laser processing input parameters in industrial applications. [ABSTRACT FROM AUTHOR]

Graphical abstract NiCoCrAlYTa coating, which possesses excellent oxidation resistance was prepared by HVOF spraying technology on the Inconel 718 substrate. And an oxidative layer with double-levels nanostructure formed on the surface of coating after different isothermal oxidation time, which presents excellent mechanical properties as well as friction and wear behaviors rate due to the the coupling effects of the gradient nanostructure of oxidative layer and the formation of amorphous protective layer on its worn surface. Highlights • The NiCoCrAlYTa coating exhibits excellent oxidation resistance in air at 1000 °C. • The oxidative layer of C3 presents double-levels structure. • The sample of C3 has excellent mechanical properties. • The friction and wear behaviors of C3 are obviously better than that of C1. • An amorphous layer forms on worn surface to improving its tribological properties. Abstract NiCoCrAlYTa coating, a metal-based coating, was prepared on Inconel 718 Ni-base superalloy substrate by high velocity oxy-fuel (HVOF) spraying. The as-polished NiCoCrAlYTa coating was heated at 1000 °C for different durations to afford coatings C1, C2, C3, and C4. The microstructure, element distribution, phase composition and crystalline structure of the as-deposited coating and heat-treated ones were analyzed by transmission electron microscopy, scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction and electron back-scattered diffraction. Moreover, the oxidation behavior of the NiCoCrAlYTa coatings was evaluated based on isothermal oxidation kinetics as well as weight loss measurements; and the effects of surface oxide layers on the microstructure, mechanical properties as well as friction and wear behavior of the NiCoCrAlYTa coatings were investigated. Results show that the as-sprayed coating exhibits dense and uniform microstructure as well as excellent oxidation resistance. Oxide layers, mainly composed of Al 2 O 3 , Cr 2 O 3 , NiO, Y 2 O 3 , Ta 2 O 5 , NiCr 2 O 4 , and CoCr 2 O 4 , are formed on the surface of the coating upon heat-treatment in air; and the microstructure and mechanical properties of the NiCoCrAlYTa coatings as well as oxide layers are governed by heat-treatment time. Particularly, coating C3, obtained after heat-treatment of the as-polished NiCoCrAlYTa coating at 1000 °C for 50 h, exhibits greatly increased indentation hardness, elastic modulus, and wear resistance. This is because the joint functions of a compact and continuous surface oxide layer with gradient nanostructure formed after heat-treatment, and the amorphous protective layer generated on the rubbed surface of coating C3. [ABSTRACT FROM AUTHOR]

Abstract A Ni-based alloy coating was fabricated on a gray cast iron surface using a multistep induction cladding technique. A scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD) were used to analyze the cross-sectional morphology, element distribution, and surface phase composition of the induction coating. The coating was metallurgically bonded to the substrate. There was a notable layered structure inside the coating. Element interdiffusion occurred at the interface between the coating and the substrate. The coating surface was composed primarily of γ-Ni solid solutions and Ni-Ni 3 Si eutectic microstructures, in which hard strengthening phases, such as borides (Cr 2 B and Ni 3 B) and carbides (Cr 23 C 6 and Cr 7 C 3), were distributed. The microhardness and wear behavior were analyzed by Vicker indentation tester and the rectilinear reciprocating testing system, respectively. The microhardness at the interface of the coating and substrate increased significantly, and the average microhardness of the coating was approximately four to five times of the substrate. At room temperature and under dry sliding conditions, as the sliding distance increased, the coefficient of slowly. As the sliding load increased, the coefficient of friction of the coating changed insignificantly, but its wear loss increased. Abrasive and oxidation wear was the dominant wear mechanism of the coating. [ABSTRACT FROM AUTHOR]

In this study, an Al–Mg 2 Si composite was solidified under a high pressure of 3 GPa and the effects on microstructural evolution, mechanical properties including hardness, friction, and wear behavior, and compression properties were investigated. The results indicate that the composite solidified under high pressure exhibited significantly enhanced hardness, compressive properties, wear, and friction resistance compared to the as-cast and solid solution–treated (ST) composites. The hardness of the composites under high-pressure solidification was 2.25 times and 1.37 times those of the as-cast and ST composites, respectively. The compressive yield strength, elastic modulus, and compressive strain were 121.5 MPa, 29.6 GPa, and 22.3% for the as-cast composite, 146.1 MPa, 44.5 GPa, and 35.8% for the ST composite, and 151.3 MPa, 49.3 GPa, and > 75% for the high-pressure-solidified composite, respectively. The friction coefficient of the composite under high-pressure solidification was only 44% of that of the as-cast composite and 67% of that of the ST composite. The wear modes were adhesive wear and abrasive wear for the as-cast composite, but only abrasive wear for the composite solidified under high pressure; the fracture mode transformed from cleavage fractures in the as-cast composite to quasi-cleavage fractures in the composite solidified under high pressure. [ABSTRACT FROM AUTHOR]

A kind of wear-resistant and lubricated Ni/N/rGO-DLC films are deposited on the surface of Ti-6Al-4V(TC4) alloy substrate by an integrative method involving pulsed electrodeposition and liquid-phase electrodeposition with various rGO (reduced graphene oxide) concentration. The growth mechanism of the film and the formation of protrusions and gully structures on the surface of the film are investigated. Furthermore, the mechanism of the effect of rGO concentration on the dispersion stability of the electrolytic system is explored. The results reveal that the Ni/N/rGO-DLC films at 0.07 g·L−1 rGO exhibit a uniform and dense structure. rGO particles are uniformly incorporated into the carbon-based films and tend to deposit perpendicular on the substrate. Simultaneously, the highest micro-indentation hardness, the lowest coefficient of friction and wear loss are obtained as 591.88 HV, 0.072 and 1.20 × 10−4 kg·m−1 of film with 0.07 g·L−1 rGO, which are principally attributed to the synergistic effect of rGO particles and amorphous carbon matrix in improving the mechanical properties of Ni/N/rGO-DLC films. [Display omitted] • The wear-resistant and lubricated Ni/N/rGO-DLC films were deposited on the surface of Ti-6Al-4V alloy substrate. • The mechanism of the formation of protrusions and gully structures on the surface of the film was investigated. • The mechanism of the effect of rGO concentration on the dispersion stability of the electrolytic system was discussed. [ABSTRACT FROM AUTHOR]

FeCrCoNiMo 0.5 W x (x = 0,0.25,0.5,0.75,1.0) HEA coatings were prepared on Q235 surfaces by laser cladding technique, the microstructure and phase composition of the coatings were analyzed to investigate the corrosion resistance, frictional wear properties, and wear mechanisms. The results showed that the increase of W caused the coating to produce μ phase, and the FeCrCoNiMo 0.5 W x HEA coating consisted of FCC solid solution and intermetallic compound σ phase and μ phase. The microstructure of the coating possesses a typical dendrite region (DR)-inter-dendrite (ID) structure, and the grain size is significantly refined after the addition of W. With the increase of W content, the microhardness and wear resistance of the coating gradually increased, among which the microhardness of W 1.0 coating was the highest and the wear resistance was the best. The wear mechanism of the coating is mainly oxidation wear, adhesive wear and slight abrasive wear. The addition of a small amount of W promotes the formation of a more stable passivation film. Further increasing the content of W, the phase content of the coating increases, resulting in a highly inhomogeneous passivation film, which reduces the corrosion resistance of the coating. The W 0.25 coating has the best overall corrosion resistance. • Enrichment of intermetallics compounds in the inter-dendrite(ID). • Debris is squeezed onto the wear surface to form an adhesion layer. • The wear mechanism is adhesive wear, oxidation wear and slight abrasive wear. • A small amount of element W promotes the formation of a more stable passivation film. [ABSTRACT FROM AUTHOR]

Hard and wear resistant coatings are useful to enhance the functional properties and improve the lifetime of mechanical components. This study proposes a relationship between microstructure and tribo-mechanical properties of TiC, CrC, ZrC and WC transition metal carbide coatings. In these coatings, an amorphous carbon (a-C) matrix phase coexists with a crystalline TMC phase. Superior wear resistance of ZrC coatings followed by the TiC coating was observed and this was explained by improved crystallinity and a-C phase present in coatings. Wear mechanisms were proposed by chemical analysis of wear tracks using micro Raman spectroscopy and energy dispersive X-ray spectroscopy. [ABSTRACT FROM AUTHOR]

Adding nano particles can significantly improve the mechanical properties and wear resistance of thermal sprayed Al 2 O 3 coating. However, it still remains a challenge to uniformly incorporate nano particles into traditional coatings due to their bad dispersibility. In the present work, nanometer Al 2 O 3 (n-Al 2 O 3 ) powders modified by KH-560 silane coupling agent were introduced into micrometer Al 2 O 3 (m-Al 2 O 3 ) powders by ultrasonic dispersion to afford nano/micro composite feedstock, and then four resultant coatings (weight fraction of n-Al 2 O 3 : 0%, 3%, 5% and 10%) were fabricated by atmospheric plasma spraying. The features and constitutes of feedstock and as-sprayed coatings, as well as their porosity, bonding strength, microhardness and frictional behaviors were investigated in detail. Results show that the nano/micro composite feedstock with uniform microstructure can be better melted in the spraying process, thereby obtaining coatings with denser microstructure, higher hardness and bonding strength. Added n-Al 2 O 3 has no obvious effect on the friction coefficient of composite coatings, whereas can improve their wear-resistant and reduce the worn degree of counterpart. The wear mechanism of traditional coating is brittle fracture and lamellar peeling, while that of composite coating with weight fraction of n-Al 2 O 3 of 10% is adhesive wear. [ABSTRACT FROM AUTHOR]

The friction and wear behavior of WC based cemented carbides ring-ring samples in different water environments were systematically tested. The average grain size of WC is 1.2 μm and the mass fraction of binder Co is 8%. The water environments include distilled fresh water, artificial seawater with NaCl mass content of 4%, and sediment water with SiO 2 mass content of 0.6% and average particle size of 88 μm. The friction torque was measured for each friction pairs at different speeds and specific pressure loads. The surface morphology of the friction pairs before and after the test were observed by a scanning electron microscope, and the weight losses were also measured by a balance. The test results suggest that the friction coefficient of all the sample pairs decreases exponentially with the increase of load at proper revolution speed. In the range of 4–10 MPa specific pressure, the friction coefficient of the bearing during stable operation is between 0.01–0.02. The wear rate of the stationary ring is about 3 times that of the matching rotary ring, no matter in the environment of artificial seawater, distilled fresh water or sediment water lubrication medium. However, the wear rates of the samples in artificial seawater are higher than those of the two rings friction under the same speed and load conditions in the other two water environments. SiO 2 particles in the sediment water has no effect on the bearings wear rate. The wear of cemented carbide self-matching pair bearings is mainly the peeling of WC particles caused by the alternating contact and friction force or plowing of WC abrasive particles. The corrosivity of artificial seawater can aggravate the peeling of WC particles. The results and conclusions of this study can provide a meaningful reference for the design of cemented carbide bearings utilized in water lubrication environment. • The wear rate of the stationary ring of cemented carbide self-matching pair is about 3 times that of the rotary ring. • The wear rate of the thrust bearing in seawater is higher than that in sediment water and distilled fresh water. • The wear of cemented carbide self-matching pair bearings is mainly the peeling of cemented carbide particles. [ABSTRACT FROM AUTHOR]

The present work aims to synthesize the CoCrNi/W/Ag x composites with the high wear-resistance under ambient air and vacuum conditions. The friction and wear properties of the CoCrNi/W/Ag x composites and CoCrNi medium entropy alloy were fully evaluated, and the chemical components and microstructural evolution of the tribo-films were observed and analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. The self-lubricating mechanism of the CoCrNi/W/Ag x composites under ambient air and vacuum conditions was investigated. Increasing the Ag content increased the thickness of the tribo-films improving the friction and wear properties of the alloys, and the thickness of the tribo-films formed on the worn surface of the CoCrNi/W/Ag 1.0 composite was about 150 nm. The CoCrNi/W/Ag 1.0 composite exhibited an evident improvement in tribological performance, with a high wear-resistance of 2.79 × 10−5 mm3/N·m under vacuum condition and a volumetric wear rate as low as 1.35 × 10−5 mm3/N·m under ambient air condition. • Semi-coherent interface improves interfacial bonding between W and Ag. • The CoCrNi/W/Ag1.0 nanocomposite has a wear rate of 1.35 × 10−5 m3/N·m under vacuum. • Increasing Ag content increases the tribo-film thickness, decreasing wear rates. • Self-lubricating and high wear-resistance mechanism was investigated under vacuum. [ABSTRACT FROM AUTHOR]

Polyimide/Epoxy resin–molybdenum disulfide bonded solid lubricant coatings (denoted as PI/EP-MoS2) were prepared. The influence of polyfluo-wax (denoted as PFW) on the microhardness and friction and wear behavior of as-prepared PI/EP-MoS2lubricant coating was measured using a microhardness tester and a reciprocating ball-on-disc tribometer, respectively. The worn surfaces of the lubricant coatings were observed with a scanning electron microscope, and their wear rate was determined with a Micro XAM surface mapping microscope. Moreover, the transfer films formed on the counterpart steel ball surfaces were analyzed by X-ray photoelectron spectroscopy. Results indicate that the incorporation of a proper content of PFW filler is effective at improving the antifriction performance of the PI/EP-MoS2lubricant coating while maintaining better wear resistance. Moreover, the friction coefficient of the lubricant coating decreases with increasing content of PFW from 2 to 10%, and the one with a filler content over 6% PFW has a steady friction coefficient of 0.07. The improvement in the antifriction performance of the lubricant coating with the incorporation of the PFW filler is attributed to the excellent lubricity of homogeneously distributed PFW. [ABSTRACT FROM PUBLISHER]

Multi-arc ion plating technology and interactive deposition process are adopted to plate TiAlN hard film on the surface of YG8 cemented carbide cutting tools. Study the influences of the coating film parameters to surface appearance with orthogonal experiment method. Observe substrate samples, TiN transition layer and TiAlN coating film under the scanning electron microscope (SEM). Cutting test, friction and wearing test showed that the coated cutting tools are with more wearing resistance. The main wear mechanisms are adhesion, some accompanied by flake layer of disbanding. Coated cutting tools significantly reduces friction coefficient. By experimental design, the best process parameters are deposition temperature 100°C, substrate negative bias voltage 250 V, nitrogen partial pressure 0.6 Pa. [ABSTRACT FROM AUTHOR]

Spray-dried mullite powder was plasma sprayed onto steel substrates to form mullite coating. The microstructure of mullite coating and its tribological properties coupled with Si 3 N 4 ball under dry sliding as well as water and hydrochloric acid solution were investigated. Results indicate that mullite coating exhibits high porosity and retains an amorphous phase. The mullite coating-Si 3 N 4 exhibits greatly reduced coefficient of friction under HCl solution, due to the boundary lubrication of the hydrated silica layer and the hydrodynamic lubrication of the acid solution. Moreover, since the wedging action of water, the mullite coating has the highest specific wear rate under water environment. [ABSTRACT FROM AUTHOR]

In order to improve the room temperature ductility and high temperature strength of Fe-25Al alloys, in situ 20 wt.%AlO/Fe-25Al composites with 0, 1, 2, 3, 4, and 5 at.% Cr element contents (0-6.70 wt.%) were prepared by mechanical alloying inducing self-propagating reaction with subsequent plasma-activated sintering. Microstructures, room temperature hardness, flexural strength, fracture toughness, and compression property and wear behavior at mid-high temperatures of the sintered samples were tested and analyzed. The results showed that all the composites with Cr element addition had good microstructure with fine grain size and high relative density. The flexural strength and fracture toughness increased first and then decreased with increasing content of Cr. Especially, the composites with 3 at.% Cr had the highest flexural strength, highest fracture toughness, and best compressive properties during 298-1073 K, and the main fracture mechanism changed from brittle fracture at room temperature to plastic deformation and pullout of the second phase at 673 K. With Cr content increasing, the friction coefficients decreased and the wear rates increased because of decreasing hardness. The composites with 3 at.% Cr had excellent wear properties with lower friction coefficient and wear rate. [ABSTRACT FROM AUTHOR]

This work focuses on the preparation of copper nanoparticles-modified polyamide 6 composites (denoted as nano-Cu/PA6) by in situ polymerization, with which cupric oxide as metallic copper source is directly reduced to metallic copper in the process of the opening-ring polymerization of ε-caprolactam only using the reducing atmosphere of reaction system. The obtained composites are characterized by means of transmission electron microscopy, X-ray diffraction, laser granulometry instrument, and ultraviolet-visible absorption spectroscopy. Moreover, the friction and wear resistance, mechanical strength, and antistatic performance of as-prepared composites are also readily evaluated. The results show that cupric oxide as filler is reduced to metallic copper and the as-reduced copper nanoparticles with 4-5-nm-size clusters separately disperse in polyamide 6 (PA6) matrix. Additionally, the addition content (mass fraction) of cupric oxide has significant effect on the crystalline form of PA6, and γ crystalline form of PA6 is predominant when higher dosage of CuO is introduced to fabricating nano-Cu/PA6 composites. Moreover, introducing a proper amount of CuO filler favors to generate nano-Cu/PA6 composites with improved mechanical properties and wear resistance. Particularly, nano-Cu/PA6 composite prepared at a CuO content of 0.5 % possesses the best tensile strength and wear resistance, showing promising application as a functional polymer-matrix composite. [ABSTRACT FROM AUTHOR]