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The inner-lined layers bonding strength of the ceramic-lined tubing was measured from 25°C to 600°C. The macroscopic structure and microscopic characteristics of the slippage surface of the ceramic-lined tubing were observed using optical microscopy and scanning electron microscopy. Combined with finite element analysis of the residual stress distribution at different temperatures, the shear failure model of the ceramic-lined tubing at different temperatures was given. The mechanical bonding force at the C-A (ceramic layer-alloy layer) interface is greater than the metallurgical bonding force at the A-T (alloy layer-base tubing) interface at low temperature, and the mechanical bonding force at the C-A interface is less than the metallurgical bonding force at the A-T interface at high temperature. The transition temperature is about 200 °C.

Several restoring technologies are employed in engine remanufacturing, such as brush electroplating, arc spraying and laser cladding, which could improve the quality and performance of the remanufactured product and the efficiency of remanufacturing processes. The primary objective of the present study is to analyze the environmental benefits of remanufacturing employing advanced restoring technologies (Scenario 3) in comparison to newly manufacturing (Scenario 1) and remanufacturing without using advanced restoring technologies (Scenario 2) based on Life Cycle Assessment (LCA) methodology. Resource and energy consumptions of each manufacturing and remanufacturing processes were collected along the production line and then the results of seven selected environmental impact categories are calculated. The results show that engine remanufacturing with advanced restoring technologies will achieve large environmental benefits. By using advanced restoring technologies, engine remanufacturing could be able to restore more damaged components and reduce the environmental impacts through reduced consumption of raw materials production and manufacturing process of production replacement parts.

Internal rotating plasma spraying has been widely used in industrial applications to enhance performance properties and prolong the service life of internal components, such as gas turbines, engine blocks, and oil pipelines. As it is difficult to dissipate the excess heat in the limited and semi-enclosed space, the temperature characteristics of the internal parts have a significant influence on the spraying process. In this study, a three-dimensional (3D) numerical model was developed to describe the temperature evolution and distribution of a cylinder under different heating modes that considers one (plasma jet only) and two contributions (plasma jet and sprayed particles), respectively. Moreover, air and water cooling modes were also implemented to alleviate the heat accumulation of the cylinder. The results indicated that heat accumulation was mainly caused by plasma jets, whereas the sprayed drops contributed slightly. The temperature increased abruptly from initial 283 to 550 K after two back and forth movements within the cylinder without the application of coolants. However, the temperature could be controlled at 420 K under the condition of air cooling and at 390 K under the condition of water cooling. Using an infrared camera and temperature sensor, experiments were conducted to validate the numerical model corresponding to the working conditions implemented in the numerical simulation. A decrease in the porosity and increase in micro-hardness of the coating could be achieved under the cooling effect of water, rather than the compressed air. The percentage improvements in the porosity and micro-hardness of the coating were approximately 14.2 and 6.1%, respectively, by the application of water cooling.

The fracture resistance of nanoscale MEMS films under high frequency impact seriously influences its service life. Nano impact test is a reliable technique to evaluate the fatigue fracture resistance of films by simulating the dynamic cyclic loading conditions. In this paper, a kind of Cu film was prepared by magnetron sputtering. The effects of loading parameters and indenter size on the fatigue damage behavior were studied for the Cu films during by nano impact test technique. The dislocation propagation and crack initiation during the nano impact process were also analyzed by molecular dynamics simulation. The results show that: Nano impact failure of Cu film can be divided into three stages and the main failure forms are cracks and delamination. The increase of the indenter radius leads to the increase of fatigue indentation size. The deformation range and damage accumulation degree of thin film material also increased correspondingly. With the increase of nano impact loading rate, the film material suffered more momentum from the indenter. The fatigue damage energy accumulation accelerates the damage.

Micro-electromechanical system (MEMS) films are subjected to a large number of impact during the working process. The fatigue life of the films need be measured to evaluate the reliability of the film's impact resistance. In this work, a new kind of MEMS soft magnetic non-equimolar high-entropy alloy (HEA) film (Fe Co Ni)25(Ti Zr Al)75 was prepared by magnetron sputtering. The fatigue damage behaviors of the HEA film was investigated by nanoscale dynamic mechanical analysis (nanoDMA) technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were adopted to analyze the microstructure and damage surfaces pattern. The results showed that the HEA film displayed a polycrystalline structure with the fcc solid solution uniformly distributed in the amorphous phase. There were three stages during the process of fatigue damage, the compressional deformation stage, the buckling and layering stage, and the edge crack propagation leads to the delamination stage. The contact stiffness suddenly decreased at the moment of fatigue damage happening.

A series of Fe-based amorphous composite coatings, mixed with ceramic particles, are prepared by flame spraying water atomized powder. The morphology, structure and mechanical properties are investigated by scanning electron microscopy, X-ray diffraction and micro- and nano-indenter, respectively. The residual stress and influence of process parameters on residual stress, such as ceramic content, type and spraying distance, have been systematically studied. The results reveal that the coating with 30 wt% Al2O3 has shown excellent properties, such as porosity of 0.5% and micro-hardness of 794.7 HV. Furthermore, the results reveal that the residual stress decreased with the addition of ceramic particles, up to a threshold value, followed by a linear increase. The maximum value of 141 MPa has been achieved for FeBSiNb coating, with the Al2O3 content of 20%. However, the high melting point of feedstock powder and high thermal conductivity of impacting ceramic particles reduce the impacting effect because of the increased enthalpy of the coating and decreased kinetic energy of the impacting ceramic particles. In addition, spraying distance can also influence the residual stress of coatings. Once the spray distance was increased from 150 mm to 250 mm, the residual tensile stress of the coating decreased from 208 MPa to −115 MPa, where negative sign signifies that the residual stress has become compressive stress.

Intrinsic structural limitations of plasma-spray TiO2 coating deteriorate its wear resistance. Herein, CNTs are incorporated in the coating to assess their effects on the microstructure and tribological properties. Structurally, degradation degree of CNTs in TiO2 matrix during plasma spraying was revealed by Raman spectroscopy. And high resolution transmission electron microscopy manifested that TiO2/CNT interface was well bonded along with presence of notable interfacial carbothermic product TinO2n-1 at atomic scale. The phenomenon indicates a beneficial effect for transferring stress from matrix to CNTs effectively. Then, the influence of CNTs on coating’s friction behavior was investigated by zirconia ball-on-disk tribometer under dry-sliding condition. As compared to TiO2 coating, the nanocomposite coating exhibited a moderate decrease in friction coefficient and an enormous reduction (∼93.6%) in wear volume. The remarkable advance in tribological properties of the reinforced coating can be attributed to four kinds of frictional effects of CNTs: tribo-reorientation, tribo-protruding, tribo-film and tribo-degradation.

The aim of present study is to monitor the delamination failure of plasma sprayed Al 2 O 3 –40 wt% TiO 2 composite ceramic coating (AT40 coating) in rolling contact condition by acoustic emission (AE) technology. The AE signals of the delamination failure process were divided into three types (type I: normal contact; type II: fatigue crack initiation; type III: delamination failure) based on the feature of AE count. The waveforms and frequency spectrums of different types of AE signals during delamination failure process of the coatings were obtained by Empirical mode decomposition (EMD) method. The relationship between the waveform/frequency of the AE signals and the delamination failure mechanism of the AT40 coatings were discussed in detail.

ASTM1045 steel was used as substrate that was laser processed with surface texturing. Ni-based coatings were deposited on the substrates using the atmosphere plasma spray technology. Surfaces with different dimples diameter and depths were acquired by adjusting the processing parameters and their effect on the bonding behavior between coatings and substrates were investigated. Scanning electron microscopy was used to characterize the cross section morphology of sprayed coatings, investigating the filling quality of coatings in the dimples. The image analysis method was also applied to calculate the contact area ratio resulting from texturing, evaluating the energy release rate at the surface/interface. XRD diffraction and nanoindentation tests were used to measure the residual stress of substrates after laser treatment and coatings near interface, respectively. The calculation analysis was carried out to research the relationship between the coating filling quality and the texturing parameters. The adhesion strength of coatings was evaluated through tensile tests. The results showed that the bond strength values present an initial increase followed by a decrease when the state of the coatings goes from full filling state to air entrance in the coatings and partial filling state following the texturing depth rising. The analysis indicates that the air volume in the dimples is determined by their diameter and depth, which are key parameters defining the filling quality as well as the adhesion strength. As the depth increases, the adhesion strength depends on the competition between residual stress caused by the presence of air and stress release due to the improvement of contact area ratio.

Alloyed layer with gradient structure was prepared on the surface of 20Cr2Ni4A steel by lanthana-bearing supersonic fine particle bombarding (SFPB). Microstructure features of the surface layer were characterized. Subsequently, the samples were carburized in an ECM vacuum furnace. Based on the experimental observations, the mechanism of promoting the diffusion of carbon atoms by lanthana-bearing SFPB was proposed. It mainly involves the promotion of the structure obtained by lanthana-bearing SFPB on the adsorption and diffusion of carbon atoms during carburization. The promotion mechanism of the rare earth in the alloying layer on carbon atom diffusion was analyzed from the aspects of accelerating mechanism of carbon source decomposition by rare earth, subsurface diffusion channel mechanism and driving force. Experimental evidence and related mechanisms show that, the structure formed by the step of austenitization during carburization and the existence of rare earth are necessary to promote the diffusion of carbon atoms. Therefore, our research results clarify the promotion mechanism of lanthana-bearing SFPB treatment on the diffusion of carbon atoms in the carburizing process, and further useful to adjust the surface structure to promote the application of pretreatment technology in surface modification.

The laser method was used to process dimples with different diameters and distances on ASTM 1045 steel substrates. Ni60 alloy powders were deposited on the textured substrates using atmosphere plasma spray technology. Single sprayed particles were collected to study the spreading behavior. Scanning electron microscopy was applied to characterize the cross-section morphology of splats and coatings, investigating the deposition behavior of droplets. Image analysis was used to calculate the open angle of first particle, thus also providing information on the subsequent particles. Transmission electron microscopy was used to investigate the crystal structure of coatings near the interface. The bonding strength of coatings was evaluated by pull-off tests. The impact of various texture parameters on the adhesion strength of coatings was investigated. The results showed that bonding strength improved with increasing texture diameter and decreasing texture distance. Wetting behavior between two particles as well as bond style between particles and substrates have great influence on bond strength of coatings with the variant texture diameter and distance. The diameter-to-distance ratio was found to be the factor directly determining the adhesion strength between substrates and coatings. Keywords: Adhesion strength, Sprayed coatings, Diameter-to-distance ratio, Deposition state, Microstructure

Friction, wear, and contact fatigue are the main causes of energy loss, material waste, and equipment failure. The aim of remanufacturing is to repair and modify the damaged equipment surface, and the surface coating is the major material that allows the remanufactured parts to be used in a new round of operation. Thus, the design and preparation of surface coatings are very important to repair, strengthen, or modify the friction pairs, in order to ensure long-term operation of the remanufactured parts. Recently, a lot of research on designing and preparing friction pair surface modification coatings has been conducted by the National Key Laboratory for Remanufacturing (NKLR). The research conducted achieved the following goals: the mechanism of micro/nano multilayer surface modification coatings with long-term efficacy life was revealed, and the corresponding design considerations and preparation methods of nanocrystalline micro tribological coatings were innovatively developed. A series of new “two-step” processes to prepare sulfide solid lubricating coatings were developed. The competitive failure mechanism of the surface coating in simultaneous wear and fatigue conditions was revealed, and some composite coatings with dual properties of wear resistance and fatigue resistance were prepared. Based on the stress distribution of friction surface contact areas and the piezoelectric effect, a failure warning intelligent coating is designed and developed. These coatings have been successfully applied to critical friction components, such as the spindle of large centrifugal compressors, engine cylinder piston components, and driver gear pairs.

The mechanical properties of a nanoscale-thickness film material determine its reliability and service life. To achieve quantitative detection of film material mechanical performance based on nanoscale mechanical testing methods and to explore the influence of loading frequency of the cycle load on the fatigue test, a TiN film was prepared on monocrystalline silicon by magnetron sputtering. The microstructure of the nanoscale-thickness film material was characterized by using scanning electron microscopy and high-resolution transmission electron microscopy. The residual stress distribution of the thin film was obtained by using an electronic film stress tester. The hardness values and the fatigue behavior were measured by using a nanomechanical tester. Combined with finite element simulation, the paper analyzed the influence of the film thickness and loading frequency on the deformation, as well as the equivalent stress and strain. The results showed that the TiN film was a typical face-centered cubic structure with a large amount of amorphous. The residual compressive stress decreased gradually with increasing thin film thickness, and the influence of the substrate on the elastic modulus and hardness was also reduced. A greater load frequency would accelerate the dynamic fatigue damage that occurs in TiN films.

The paper deals with the quantitative characterization of spreading morphologies of plasma sprayed Fe-based alloy droplets deposited on mirror polished steels with different preheated temperature. The plasma torch was utilized as heat producer. The influence of substrate temperature on the solidification mechanism of molten droplets was investigated. The image analysis method (IMA) was employed to identify single splat from the field emission scanning electron microscope (FE-SEM) morphology. The result shows that the substrate preheated temperature has a significant effect on the flattening behavior of molten droplets. With the increment of substrate temperature, the solidification mode of splat changes from flower-like and splashed splat to disk-like splat due to the modification of wettability and cooling velocity between molten droplet and substrate. Compared with area and perimeter, both fractal dimension (FD) and solidity could separately detect the solidification mode of splat to a certain extent, while the FD seems to be more excellent in characterizing irregular morphology of splat in contrast with solidity. However, the combination of FD and solidity is more efficient in classifying solidification mode of splat.

Surface texture was prepared on the ASTM1045 steel substrate before spraying. Three texturing patterns (groove pattern, square pattern, and hexagon pattern) were acquired by laser processing to investigate the influence of texturing patterns on the adhesion strength of sprayed coatings. The Ni60 coatings were prepared on the textured surface by atmosphere plasma spraying technology. Scanning electron microscopy and laser 3D microscope were used to characterize the morphology of texturing. The adhesion strength between coating and substrate was examined by the tensile test. Image pro plus software was used to calculate the contact area ratio of the textured substrate. The results show that the texturing processed substrates by laser radiation present plain area between two dimples and the protrusion around texturing, and the contact area between coating and substrate is increased. The adhesion strength of coatings with a groove pattern, a square pattern, and a hexagon pattern is 58, 33, and 47 MPa, respectively. The adhesion strength of sprayed coatings varies with the change of the texturing pattern, and it does not only depend on the contact area ratio but also on the texturing density and the texturing microstructure.

Metal magnetic memory testing (MMMT) is a promising nondestructive technique for early damage evaluation of ferromagnetic materials due to its high sensitivity to the stress state. An experimental investigation of the effect of axial applied stress on MMMT signals, both the normal component B z and the tangential component B x , under on-line loaded and unloaded measurement condition has been carried out during the whole tensile test in 0.45%C steel. In the elastic deformation stage, B z signal kept rotating counterclockwise while B x signal kept moving upward under on-line measurement both when loaded and unloaded, but the MMMT signals measured unloaded tended to resume the initial state compared those measured loaded. In the plastic deformation stage, B z signal rotated clockwise while B x signal moved downward under on-line loaded measurement with the increase of tensile stress, while the MMMT signals measured unloaded reversed compared those measured loaded. The results of the present work indicate that MMMT is a feasible solution for stress state on-line monitoring of ferromagnetic components.

Four types of W-doped graphite-like carbon (W-GLC) films were deposited under different W target currents by magnetron sputtering method. The effects of W content on the microstructure and properties of the W-GLC films were analyzed via various characterization techniques. The results show that the microstructure of the W-GLC films tends to be loose, while the surface roughness distinctly increases with the increase in the W target current. Moderate W-doping can considerably improve the mechanical properties and wear resistance of the film, which will subsequently decrease as the W content becomes excessive. Moreover, the friction coefficient of the W-GLC films does not show a distinct change, but significantly increases when the W target current increases from 0.9 A to 1.2 A. In particular, when the W target current is 0.6 A, the friction coefficient and the wear rate of the W-GLC film are 0.02 and 3.8 × 10−17 m3/N·m, respectively, exhibiting excellent tribological properties.

The enrichment of copper from copper–cyanide wastewater by solvent extraction was investigated using a quaternary ammonium salt as an extractant. The influences of important parameters, e.g., organic-phase components, aqueous pH values, temperature, inorganic anion impurities, CN/Cu molar ratio, and stripping reagents, were examined systematically, and the optimal conditions were determined. The results indicated that copper was effectively concentrated from low-concentration solutions using Aliquat 336 and that the extraction efficiency increased linearly with increasing temperature. The aqueous pH value and concentrations of inorganic anion impurities only weakly affected the extraction process when varied in appropriate ranges. The CN/Cu molar ratio affected the extraction efficiency by changing the distribution of copper–cyanide complexes. The difference in gold leaching efficiency between using raffinate and fresh water was negligible.

TiO2-12 wt% Al2O3 coating was deposited on engine cylinder surface by internal plasma spraying to optimize the cylinder-piston tribosystem. The tribological tests were conducted under lubricated conditions on SRV4® reciprocating tribometer. To simulate engine acceleration from cruise to full power, friction parameters of load, frequency and temperature were designated to change over a wide variation, namely 53–157 N, 35–45 Hz and 85–197.5 °C respectively. Accordingly, triboscopic 4D-maps were plotted originally to exhibit the evolution of friction coefficient. Results also showed that cylinders after coating had significant improvement of tribological properties compared with the uncoated specimens, which can be attributed to the great chemical stability to oil, smooth surface roughness during friction, high hardness and H/E of the ceramic coating.

The paper aims at the investigation of the effect of slip ratio on the rolling contact fatigue (RCF) performance of Fe-based alloy coatings. A double-roll test machine is employed to perform the experiment. The result shows that slip ratio has a significant influence on the RCF performance of Fe-based coating. With the increment of the slip ratio, the RCF failure life keeps decreasing but the shape parameter β of Weibull mode decreases first, then increases. The failure mechanism under pure rolling contact condition is the accumulation of micro-pits and the propagation of fatigue cracks within the coating. However, under nonzero slip ratio condition, failure is controlled by the coupling of the cyclic loading action and of the friction force.

Very high cycle bending fatigue behaviors of FV520B steel under fretting wear were studied by the ultrasonic fatigue technique. The specimen system for ultrasonic bending testing was designed and the stress distribution of fatigue specimen was obtained by finite element method. The microstructure of FV520B steel was characterized by means of optical microscope, transmission electron microscope, and energy-dispersive spectroscope. The P–S–N curve was drawn based on fatigue data. The micromorphology characteristics of fretting wear surface and fracture surface for fatigue specimen were observed. The results indicate that the microstructure of FV520B steel is mainly composed of lath martensite, ferrite, and precipitation particles, with some randomly distributed internal inclusions. The P–S–N curve shows that there exists no “conventional fatigue limit” and the fatigue life decreases continuously with the increase of applied stress Smax. Most of fatigue cracks are observed on fractography and initiate from the overlap region of fretting wear zone and stress concentration zone. The fracture failure for tested specimen is ascribed to fretting wear and bending vibration fatigue.

A detector combining indentation method and acoustic emission (AE) technique was developed for evaluating the bonding strengths of sprayed coatings. In order to study the effect of indentation conditions on cracking failure behavior of sprayed coating, FeCrBSi coating was prepared by plasma spraying technique. The AE signals during indentation test were abstracted and investigated. The morphologies of indented samples were observed by scanning electronic microscopy (SEM). The results indicate that indentation equipment can induce the cracking failure of coating and AE technique can define the critical statues. The test by interior load was feasible and accurate for evaluating the bonding strength. The key influential factor of indenter lied in the contact area between indenter and coating. The loading rate had little effect on AE signal. The loading conditions were optimized to use diamond indenter with interior load and a loading rate of 100 pulses per second.

The rolling contact fatigue (RCF) failure procedure of Fe-based alloy coating, fabricated by high efficient plasma spray (PS) technology, was investigated by a double-roller test machine with oil lubrication under pure rolling contact condition. The fractal dimension (FD) was utilized to quantitatively characterize the profile of the worn surface at different experiment stage and the failure mechanism of the coating was discussed. The results indicated that the nonlinear morphologies of the worn surface of Fe–Cr alloy coating possessed excellent fractal properties. The failure procedure could be divided into four stages according to the value and change rule of FD, i.e. (1) running-in stage, (2) stable abrade stage, (3) accelerated damage stage, (4) unstable removal stage.

The purpose of this paper is to evaluate whether over-speed centrifugal force can cause fatigue damage to the welded impeller. Two non-destructive testing techniques of Acoustic Emission (AE) and Infrared Thermography (IRT) were combined to predict the fatigue limit of FV520B and its welded joint. The results indicated that the maximum stress of plastic creep shakedown stage judged by a time–displacement curve was close to the high-cycle fatigue (HCF) limit predicted by the IRT method. The AE technology might have ability to predict the ultra-high cycle fatigue (UHCF) limit. Furthermore, under the present over-speed preloading process, this impeller is located at the pure elastic stage without any fatigue damages.

Internal rotating plasma spraying (IRPS) plays an important role in improving the properties and prolonging the service life of internal parts and components of mechanical systems. IRPS is conducted in the confined and semi-enclosed spaces at a spraying distance of 30–70 mm to coat the engine cylinders of automobiles or heavy equipment. Occasionally, particles cannot be appropriately treated in the plasma flow, and owing to several factors, the particles remain suspended in the air rather than being deposited onto the substrate. Consequently, the suspended particles are difficult to remove efficiently within the confined space, and can thus have severe effects on the properties of coatings, including porosities and inclusions. It is therefore essential to develop appropriate methods to avoid defects in the coating by removing suspended particles inside the cylinder. In this study, numerical simulations were conducted to investigate the flow-velocity field and particle-mass-concentration distribution within the cylinder. The flow-velocity and particle mass concentration in the cylinder space were analyzed under different working conditions that can induce different suction pressures driven by a three-phase asynchronous motor connected to the bottom of the cylinder by a suction tube. The results showed that the flow-velocity field is symmetrical along the axis of the cylinder and the mass concentration of particle is concentrated on the region from middle to bottom of the cylinder, under the effect of the suction pressure. In addition, the low-velocity and high-particle-mass-concentration regions are mainly located in the vicinity of the internal wall. Furthermore, the flow velocity was measured using a hot-wire-anemometer and the coating microstructure was observed using scanning electron microscope (SEM). We compared numerical simulation results and experimental measurements, which validated the flow-velocity field directly and the distribution of particle mass concentration indirectly. Based on the numerical results that consider the removal degree of suspending particles and the stability of the plasma jet, it can be determined that the optimal suction pressure is −100 Pa for decreasing dust pollution during the spraying process.

Stress in laser cladding coating is an important factor affecting the safe operation of remanufacturing components. Ultrasonic testing has become a popular approach in the nondestructive evaluation of stress, because it has the advantages of safety, nondestructiveness, and online detection. This paper provides a review of ultrasonic testing for stress in remanufacturing laser cladding coating. It summarizes the recent research outcomes on ultrasonic testing for stress, and analyzes the mechanism of ultrasonic testing for stress. Remanufacturing laser cladding coating shows typical anisotropic behaviors. The ultrasonic testing signal in laser cladding coating is influenced by many complex factors, such as microstructure, defect, temperature, and surface roughness, among others. At present, ultrasonic testing for stress in laser cladding coating can only be done roughly. This paper discusses the active mechanism of micro/macro factors in the reliability of stress measurement, as well as the impact of stress measurement on the quality and safety of remanufacturing components. Based on the discussion, this paper proposes strategies to nondestructively, rapidly, and accurately measure stress in remanufacturing laser cladding coating.

Stess in laser cladding coating is an important factor affecting the safe operation of remanufacturing components. Ultrasonic testing has become a hot direction in nondestructive evaluation of stress, because it has the advantages of safety, non-destructive and on-line detection. This paper provides a review of ultrasonic testing for stress in remanufacturing laser cladding coating. It summarizes the recent research outcomes on ultrasonic testing for stress, analyzes mechanism of ultrasonic testing for stress. Remanufacturing laser cladding coating shows typical anisotropic behaviors, the ultrasonic testing signal in laser cladding coating is influenced by many complex factors, such as microstructure, defect, temperature and surface roughness, etc. At present, ultrasonic testing for stress in laser cladding coating can only be done roughly. The paper discusses active mechanism of micro / macro factors to the reliability of stress measurement and the impact of stress measurement to the quality and safety of remanufacturing components. Base on the discussion, the paper proposes strategies for acquisition of nondestructive, rapid and accurate measurement of stress in remanufacturing laser cladding coating.

this paper investigated on influence of WC–Ni addition on rolling contact fatigue (RCF) behavior of NiCrBSi coating. The results showed that WC–Ni addition significantly influenced on failure mode of NiCrBSi coating especially under low stress, whereas both coatings failed in identical mode under relatively high stress. WC–Ni addition also had a specific influence on RCF lives. RCF Lives of NiCrBSi/WC–Ni coating were longer than NiCrBSi under low stress, but they were almost same under relatively high stress. RCF life distribution of NiCrBSi/WC–Ni coating was more concentrated than NiCrBSi. Besides, there was a potential relationship between Weibull slope and failure mode.

Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath. The coating consists of massive equiaxial crystals with an average grain size of about 24 nm and exhibits a (111) preferred orientation. The differential scanning calorimetry (DSC) analysis of nanocrystalline nickel demonstrates that the peak temperature of rapid grain growth is about 285.4 °C, and the peak temperature of grain growth towards equilibrium is around 431.5 °C. The isochronous annealing results reveal that abnormal grain growth behavior is not observed in nanocrystalline nickel without sulfur-containing. The thermal stability of the deposition was improved due to its initial microstructure of the as-deposited nickel and a certain amount of annealing nano-twins with low-energy, which reduces the driving force for grain growth. Consequently, the coating shows a low residual tensile stress of about 50 MPa and a high microhardness of HV 400 at the annealing temperature of 450 °C.

Numerical simulation and experimental results were employed for the identification of the most vulnerable zones in three-pass cold-metal-transferring (CMT) welded joint. The residual stress distribution in the joint was predicted by finite element (FE) method, while the structural morphology of distinctive zones was obtained through metallographic experiments. The highest principal stress made the symmetric face of the joint most sensitive to tensile cracks under service conditions. Whereas, the boundaries between the weld seam and the base plates were sensitive to cracks because the equivalent von Mises stress was the highest when the first interpass cooling was finished. The third weld pass and the inter-pass remelted zones exhibited the modest mechanical performances as a result of the coarse grain and coarse grain boundary, respectively. The most vulnerable zones were regarded to be the crossed parts between the zones identified by numerical and experimental methods.