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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.

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 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.

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.

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.

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.

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.

In this paper, the properties of NiCrBSi/WC–Ni composite coatings deposited by plasma spraying were analyzed, including their microstructure, element distribution, phase composition, porosity, and microhardness. The rolling contact fatigue (RCF) life and failure modes were also investigated. The results showed that the NiCrBSi/WC–Ni composite coating exhibited a typical lamellar structure. Furthermore, evenly distributed W 2 C/WC phases were well wetted by other phases. In addition to WC and W 2 C phases, the NiCrBSi/WC–Ni composite coating consisted mainly of γ-Ni, Cr 7 C 3 , Cr 23 C 6 , FeNi 3 , Ni 3 Si, CrB, and NiC. The study also found that the NiCrBSi/WC–Ni composite coating (porosity of 1.84%) had a slightly lower density than the NiCrBSi coating (porosity of 1.62%). The microhardness of the NiCrBSi/WC–Ni composite coating was significantly enhanced by the addition of hard WC–Ni. Furthermore, the results indicated that the NiCrBSi/WC–Ni composite coating had a higher dispersion degree of the RCF life and a longer life than the NiCrBSi coating under 0.881 GPa. Therefore, under this stress level, the RCF performance of the NiCrBSi/WC–Ni composite coating was superior to that of the NiCrBSi coating.

Mechanical behavior and fatigue properties greatly influence the reliability and life of film materials. Quantitative testing of film fatigue property under dynamic load is realized on the basis of nanometers thick Cu films deposited on monocrystalline silicon substrates by magnetron sputtering system. Microstructure and surface pattern of copper films are characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Film hardness and modulus are measured by quasi-static test and continuous measurements (CMX) systems of nanomechanical testing instrument. Fatigue damage behaviors are investigated by nanoscale dynamic mechanical analysis (nanoDMA) technique. The results indicate that Cu films prepared by magnetron sputtering system present (1 1 1) preferred orientation and contain a large number of nanoscale grains with uniform texture and low roughness. As is affected by substrate and small scale effect, CMX method is more suitable than quasi-static method for the measurement of micro-mechanical properties of ultra-thin films. Fatigue dominantly happens in thinner films. Factors, like thickness, inner stress, modulus and hardness, can influence fatigue life of nanoscale Cu films.

In order to prepare the PbTiO 3 coating with high density and excellent piezoelectric properties on all kinds shape surface, the PbTiO 3 coating was prepared by supersonic plasma spraying. The microstructure and mechanical properties were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectrograph (XPS). The dielectric constant and dissipation constant of the PbTiO 3 coating were tested. The results show that the coating has a single ferroelectric phase with perovskite structure, and its surface is smooth and dense. In the course of spraying, about 50% PbTiO 3 is decomposed into PbO and TiO 2 at high temperature. The ferroelectric hysteresis is weak and the ferroelectric hysteresis loop is not completely closed, which indicates that the defects, such as pores and cracks, exist in the coating. Although the defects are inevitable, the PbTiO 3 coating with ferroelectric and piezoelectric properties is successfully prepared.

The critical plasma spraying parameter (CPSP) is a significant factor to influence the quality of plasma-sprayed coatings. The aim of this work was to investigate the effects of the CPSP on microstructure and mechanical properties of nanostructured alumina–13 wt.% titania (n-AT13) coatings prepared by supersonic plasma spray (SPS). The microstructure, phase composition, porosity, micro-hardness, Young's modulus and fracture toughness of coatings were characterized and experimentally measured. The results revealed that the values of porosity, micro-hardness, Young's modulus and fracture toughness followed Weibull distribution and had wide ranges. The microstructure of the coating consisted of fully melted regions and partially melted regions, which resulted in a bimodal distribution characteristic of mechanical properties. With the increase of CPSP, there were two contradictory trends. The mean values and characteristic values of both porosity and fracture toughness decreased rapidly and then slowly to a local minimum, while values of both micro-hardness and Young's modulus were on the contrary trend. Moreover, the characteristic values of micro-hardness and Young's modulus were decreased functions of those of porosity, and the opposite tendency for the characteristic value of fracture toughness.

Nanostructured Al 2 O 3 -13 wt.%TiO 2 (n-AT13) ceramic coatings were fabricated by supersonic plasma spray (SPS) using agglomerated powders. Effects of the argon gas flow rate (AGFR) on microstructure and micromechanical properties of n-AT13 ceramic coatings, which have been widely used to improve the wear and corrosion resistance, were investigated. The microstructure, porosity, micro-hardness, elastic modulus and fracture toughness of coatings were experimentally determined and characterized. The results showed that the measured data of micro-hardness, elastic modulus, fracture toughness and porosity followed Weibull distribution and had a large scattering. Micro-hardness, elastic modulus and fracture toughness exhibit a characteristic of bimodal distribution because of a bimodal distributional microstructure, which was composed of fully molten regions (FM) and partially molten regions (PM). With the increasing AGFR, the mean values and characteristic values of micro-hardness as well as elastic modulus increased and reached a local maximum and then decreased. However, the mean values and characteristic values for porosity as well as fracture toughness had opposite trends. Characteristic values and mean values of fracture toughness increased with the increase in values of porosity, but those of micro-hardness and elastic modulus were opposite.

A required finite element method (FEM) model applicable for narrow gap CMT and CMT+P MIX welding was established based on the interactions between arc, base metal and filler metal. A novel method of simplifying wire feeding pulses and heat input pulses was supposed under the conduction of equivalent input. The method together with composed double-ellipse heat sources was included in the model. The model was employed in the investigation of thermal cycling and the identification of the softened zone of AA7A52 base plates. Low-frequency behavior emerged in the form of low-cooling rate sects, which were not expected under experimental conditions. The softened zone including the quenched zone and averaging zone of the base plate was much wider internal the base plate than that close to the surfaces. The reliability of the predictions in thermal cycling was supported by infrared imaging test results of the thermal cycle process.

The influence of contact stress on rolling contact fatigue performance of plasma sprayed Al2O3–40 wt% TiO2 composite ceramic coating was investigated using a double-roll test machine under pure rolling contact condition. The shear stresses within the coating were analyzed with the three-dimensional finite element method. Three modes of failures, i.e., surface abrasion, spalling, and delamination, were observed during this investigation. The failure mechanisms of surface abrasion, spalling, and delamination were discussed in detail. The initiation and propagation of fatigue cracks were mainly caused by the shear stress, which were highly influenced by the contact stress.

The competing failure mechanism and life prediction of plasma sprayed Al 2 O 3 -40 wt%. TiO 2 composite ceramic coatings under rolling-sliding contact conditions were investigated on a double-roll test machine. The maximum shear stress distribution in the coatings was analyzed by the finite element method. Weibull function was used to characterize the life distribution of the coatings under different rolling–sliding contact conditions. The failure modes were mainly surface abrasion and adhesive delamination during this investigation. The mechanism of the competing between surface abrasion and adhesive delamination was discussed in detail.

The objective of the present study is to characterize the Fe-based alloy coating deposited by the supersonic plasma spraying process. The condition of the melting particles was in situ monitored. The microstructure of the coating was examined by scanning electron microscope and high resolution transmission electron microscope. The phase composition was examined by X-ray diffraction. The microhardness and porosity were also measured, respectively. Results show the prepared coatings have excellent properties, such as few oxides, high microhardness and a low porosity amount. At the same time, a mass of amorphous/nanocrystalline phases was found in the coating. The mechanism of the formation of amorphous/nanocrystalline phases was investigated. The appropriate material composition of spraying material and flash set process of plasma spraying are the key factors. Moreover, the mechanism for oxidation resistance is also investigated, where the separation between melting metal and oxygen by the formation of SiO2 films is the key factor.

A novel rolling contact fatigue (RCF)/wear competitive life test machine based on double-roll mechanism was designed to investigate the RCF/wear failure mode and predict the competitive life regularity of surface coatings. The test machine was designed for variable slip ratio to simulate the complex service conditions. The failure can be monitored using signals which are acquired from acoustic emission (AE) of the contacting rollers. In the experimental studies, the typical morphologies of RCF damage such as pits, surface abrasion, and delamination were observed. The effectiveness of the AE signals used as a RCF failure monitoring tool was analyzed. The P–N and P–S–N plots were established to predict the life regularity of surface coatings.

In order to expand the application field of MoS 2 lubricant coatings (films) and to improve their adaptability in harsh environments, a Ni/MoS 2 –C composite coating composed of Ni metallic matrix and two lubricating components was prepared on AISI 52100 steel substrates with a nano electro-brush plating process. The relationship between microstructure and properties of the coating was analyzed via microstructure characterization. The tribological properties of the as-received coating samples and the samples treated in humid air (HA), high vacuum (HV), atomic oxygen (AO) erosion and ultraviolet (UV) irradiation exposure were investigated comparatively. The results show that the surface of the obtained Ni/MoS 2 –C coating is smooth and clean. The micro and nano MoS 2 –C grains are dispersed in the Ni matrix homogeneously. The MoS 2 and C particles also showed good synergistic effects. The added nano graphite particles not only increased the moisture resistance of the composite coating, but also reduced the residual stress and enhanced the mechanical properties of the coating. The composite coating still showed good lubricating properties after long-duration treatments in HA, HV, AO and UV environments, and the friction coefficients during the stable running periods remained at about 0.1. The influence of vacuum outgassing on the properties of the lubricants is not obvious. The coatings were oxidized slightly by AO, and thus their initial friction coefficients in AO conditions also increased, but the coating still showed good friction reduction properties after a short running-in period. The changes in microstructure and properties of the coating after UV irradiation were also inconspicuous. All test results indicate that the Ni/MoS 2 –C composite coating has excellent space tribological properties and good adaptability in harsh environments. So it is promising to use Ni/MoS 2 –C composite coating in a space solid lubrication area.

Acoustic emission (AE) technique was used to monitor rolling contact fatigue (RCF) experiments of plasma sprayed coatings. AE signal response was investigated. Worn morphologies of the coating were observed. Results show that typical AE signal mode owns three stages, i.e. running-in, stable and jump stage. Observations of worn coating release there are three kinds of AE signal sources, i.e. the crack initiated from surface, cracks embedded within the coating and cracks on the coating/substrate interface. The combined effect of orthogonal shear stress (OSS) and radial stress (RS) is main reason of the initiation and propagation of cracks within the coatings.

Experimental measurements were used to investigate the effect of residual stress on the nanoindentation of (100) copper single crystal. Equi-biaxial tensile and compressive stresses were applied to the copper single crystal using a special designed apparatus. It was found that residual stresses greatly affected peak load, curvature of the loading curve, elastically recovered depth, residual depth, indentation work, pile-up amount and contact area. The Suresh & Giannakopoulos and Lee & Kwon methods were used to calculate the residual stresses from load-depth data and morphology observation of nanoindents using atomic force microscopy. Comparison of the obtained results with stress values from strain gage showed that the residual stresses analyzed from the Suresh & Giannakopoulos model agreed well with the applied stresses.

In this paper, the residual stress in the plasma-sprayed FeCrBSi coating was determined by nanoindentation and X-ray diffraction (XRD). The XRD results showed that tensile residual stress was generated in the FeCrBSi coating, and the through-thickness values range between 40 MPa and 112 MPa. The residual stress measured by nanoindentation is 753 MPa. The difference between the XRD and nanoindentation results was discussed. It is found that the factors limiting the nanoindentation measurement of residual stress include the ‘sink-in’ deformation around the indenter, the roughness of the FeCrBSi coating, and the use of reference sample without residual stress. The above three factors lead to the over-prediction of residual stress by nanoindentation.

A composite Zn/ZnS coating was prepared by a novel compound technology-combining high velocity arc spraying and low temperature ion sulfurizing in this paper. The surface and cross-section morphologies were observed by scanning electron microscopy (SEM). The X-ray diffraction (XRD) pattern for the Zn/ZnS coating implies that it mainly consists of Zn and ZnS. The nanohardness and elastic modulus were measured by a nano-indentation tester. The tribological behaviors were investigated on a ball-on-disk wear tester under dry condition. The results showed that the friction coefficient and worn depth of the composite Zn/ZnS coating were low and stable, indicating that it had excellent friction-reduction and anti-wear properties under dry condition.

In this study, the FeS/ferroalloy composite coating with the upper FeS coating and the lower ferroalloy welding coating was prepared on the 1045 steel by a compound technology—metal-arc inert-gas (MIG) welding and low temperature ion sulfurizing. The surface morphologies, phase structure and mechanical properties of the FeS/ferroalloy composite coating have been characterized by surface analysis methods such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and nano-indentation tester. The SEM images showed that the surface of the FeS/ferroalloy composite coating was homogeneous and smooth, and the thickness of the FeS layer obtained from ion sulfurizing was about 3 μm. The EDS analysis results proved that the light gray belt zone in the cross-section morphology was the FeS layer. The XRD patterns implied the FeS/ferroalloy composite coating was composed of FeS, α-Fe and Fe–C solid solution. The coated disc slided against an AISI 52100 ball under dry friction condition. The results showed that the FeS/ferroalloy composite coating exhibited low friction coefficient and high wear-resistance.

Surface nanocrystallization of 1Cr18Ni9Ti austenite stainless steel was conducted by the supersonic fine particles bombarding (SFPB) technique. The friction coefficients and wear losses in air and vacuum were tested to analyse the effect of surface nanocrystallization on the tribological properties of 1Cr18Ni9Ti steel. The results show that the microstructure of the surface layer was refined into nano-grains successfully by SFPB treatment; furthermore, strain-induced martensitic transformation occurred during the treatment. The tribological properties of SFPB treated samples enhanced greatly, The dominant wear mechanism of the original 1Cr18Ni9Ti stainless steel is abrasive wear and adhesive wear, while it transfers to the combined action of fatigue wear, abrasive wear and adhesive wear after surface nanocrystallization by SFPB.

A sulfide film was fabricated on the nanocrystalline layer of 1Cr18Ni9Ti stainless steel by a two-step method of supersonic fine particles bombarding (SFPB) and low temperature ion sulfurization treatments. The microstructure and mechanical properties of the nanocrystallized surface and the sulfide film were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy (equipped with EDS), augur energy spectroscopy, X-ray photoelectron spectroscope, and nano-indenter. The tribological behaviour of the treated (after SFPB and sulfurizing treatments) 1Cr18Ni9Ti steel in vacuum was investigated on a ball-on-disk tribometer. The results showed that, randomly oriented equiaxial nanograins with the mean grain size less than 30 nm were formed in the top surface layer of the SFPB treated sample, and a compact and uniform sulfide film mainly composed of FeS was obtained after the succedent sulfurizing treatment. Compared to the original 1Cr18Ni9Ti steel, the treated surface revealed lower friction coefficient and better wear resistance in vacuum, and the variation of tribological properties with atmospheric pressure of the treated samples was not significant. The dominant wear mechanisms of the treated 1Cr18Ni9Ti in vacuum were abrasive wear and fatigue wear.

The rolling contact fatigue (RCF) failure prediction of the coating Fe–Cr alloy coatings was investigated. The acoustic emission (AE) technique was used to monitor RCF tests of the coatings. The failure mechanism was investigated. Results showed AE signals sensitively detected the initiations and propagations of the fatigue cracks within the coatings before the obvious surface material losses. AE signals also reflected the cumulate damage procedure. So the coming RCF failures can be predicted by AE signal responses. Moreover, the micro-defects within the coatings were considered to be the fatigue crack origins.

In this paper, the residual stress in quenched AISI 1045 steel was measured by a recently developed nanoindentation technique. Depth control mode was adopted to measure the residual stress. It was found that residual compressive stress was generated in the quenched steel. The material around nanoindents exhibits significant pile-up deformation. A new method was proposed to determine the real contact area for pile-up material on the basis of invariant pile-up morphology of the loaded or unloaded states. The results obtained by the new method were in good agreement with the residual stresses measured by the classical X-ray diffraction (XRD) method.

A nanocrystalline surface layer of 10 μm thickness was fabricated on 1Cr18Ni9Ti stainless steel by means of supersonic fine particles bombarding (SFPB). The followed low-temperature ion sulfurizing was carried out on the original and the SFPBed (SFPB treated) surface, respectively, forming sulfide layers with certain thickness. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to analyze the phase constituents and grain size of the nanocrystallized surface layer. The surface morphologies and compositions of the sulfide layers were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray photoelectron spectroscope (XPS) was used to detect the valence states of the sulfide layers. Elemental distribution with depth was measured by augur energy spectroscopy (AES). The results show that the microstructure of the surface layer is refined to nano-grains with the grain size about 30 nm and random crystallographic orientations by SFPB treatment. The surface nanocrystallization pretreatment can significantly improve the thickness, density, and the FeS content ratio of the sulfide layers. The analysis indicates that, the enhancement in efficiency of the ion sulfurization treatment by SFPB surface nanocrystallization treatment is mainly attributed to the high-density crystal defects and the increase of surface chemical activity.

In this paper, we develop a method for determining the hardness of FeCrBSi coating on a 1045 steel substrate. The nano-indents of the FeCrBSi coating exhibit obvious pile-up. The proposed method models the projected contact area as an equilateral triangle bounded by arcs to correct for the effect of pile-up on the contact area. The new method is described in detail and leads to improvement in obtaining coating hardness compared with the widely adopted Oliver–Pharr method.

The aim of this paper was to address the influence of undercoating on the rolling contact fatigue (RCF) performance of coatings. The Fe-based alloy and Ni/Al alloy were deposited on substrates as surface coating and undercoating by plasma spraying. The failure modes were investigated for two kinds of coatings. RCF performances were compared using Weibull distribution plot. The results showed undercoating played an important role on increasing RCF life of coating for the higher bond strength, and decreasing the scatter of RCF life data. The deposited undercoating could influence the failure mode of coating and prevent the occurrence of catastrophic delamination.

The 3Cr13 coating was prepared on the surface of 1045 steel by high velocity arc spraying method, and then treated by low temperature ion sulfuration to obtain the solid lubrication composite 3Cr13/FeS layer. SEM was used to observe the surface, cross-section and worn scar morphologies. XRD was utilized to analyze the phase structure. X-ray stress determinator was utilized to measure its residual stress. The nano-hardness and elastic modulus of composite 3Cr13/FeS layer were surveyed by the nano-indentation tester. The tribological properties were investigated on a ball-on-disk wear tester under dry and oil lubrication conditions. The results showed that the friction coefficient and wear scar depth of the composite 3Cr13/FeS layer were always lower than those of FeS film and 1045 steel under dry and oil lubrication conditions. Therefore the composite 3Cr13/FeS layer had excellent Friction-reduction and anti-wear properties.

The W film was prepared on 1045 steel by magnetron sputtering, with the thickness of 2 μm, its surface and cross-section morphologies were investigated with SEM, and the phase structure was analyzed with XRD. X-ray stress determinator was utilized to measure its residual stress, and the nano-hardness and elastic modulus of the film were surveyed by nano-indentation tester. The results show that the surface of W film is very compact and smooth; the particles arranged regularly, the granularity of the thin film is about 1 μm. The microcracks, cavities and desquamation were not found in the film and interface, and the bonding between the W film and substrate is well. The XRD results showed that the W film had a body-centered cubic structure, the lattice constant: a = 0.316 nm, the growth preferred orientations are (1 1 0) and (2 2 0). The compressive stress (−169 MPa) was found on the surface. The average nano-hardness and elastic modulus of W film are 15.22 GPa, 176.64 GPa, respectively, and the mechanical properties of W film are well.

Wear and friction properties of surface modified Cu nanoparticles as 50CC oil additive were studied. The effect of temperature on tribological properties of Cu nanoparticles was investigated on a four-ball tester. The morphologies, typical element distribution and chemical states of the worn surfaces were characterized by SEM, EDS and XPS, respectively. In order to further investigate the tribological mechanism of Cu nanoparticles, a nano-indentation tester was utilized to measure the micro mechanical properties of the worn surface. The results indicate that the higher the oil temperature applied, the better the tribological properties of Cu nanoparticles are. It can be inferred that a thin copper protective film with lower elastic modulus and hardness is formed on the worn surface, which results in the good tribological performances of Cu nanoparticles, especially when the oil temperature is higher.

A typical 321 stainless steel/aluminum composite coating (321/Al coating) was prepared by high velocity arc spraying technique (HVAS) with 321 stainless steel wire as the anode and aluminum wire as the cathode. The traditional 321 stainless steel coating was also prepared for comparison. Tribological properties of the coatings were evaluated with the ring-block wear tester under different conditions. The structure and worn surface of the coatings were analyzed by scanning electron microscopy(SEM), X-ray diffractometry(XRD) and energy dispersion spectroscopy(EDS). The results show that, except for aluminum phase addition in the 321/Al coating, no other phases are created compared with the 321 coating. However, due to the addition of aluminum, the 321/Al coating forms a type of “ductile/hard phases inter-deposited” structure and performs quite different tribological behavior. Under the dry sliding condition, the anti-wear property of 321/Al coating is about 42% lower than that of 321 coating. But under the oil lubricated conditions with or without 32 h oil-dipping pretreatment, the anti-wear property of 321/Al coating is about 9% and 5% higher than that of 321 coating, respectively. The anti-wear mechanism of the composite coating is mainly relevant to the decrease of oxide impurities and the strengthening action resulted from the “ductile/hard phases inter-deposited” coating structure.

Composite coatings of nickel with G particles were produced on AISI 1045 carbon steel substrate by using a newly developed automatic brush plating system. Pure nickel coating was also prepared for comparative study. The volume percent incorporation of G powder in the composite coatings was investigated with respect to its concentration in bath and relative anode to cathode speed. It was shown that the volume percentage of G was strongly affected by these parameters. The G particle distribution in the composite coatings was uniform across the coating at low concentration of G in bath and agglomerated on the surface at high concentrations. The wear and friction properties of G–Ni composite coatings containing different amounts of G particles were studied. The results revealed that hardness, wear resistance and friction coefficient are dependent on volume percentage of G in composite coating. In this study, it was shown that G–Ni composite coating with 15% G possessed the best wear-resistance property.

The microstructures of three kinds of the synthetical solid FeS, acting as the solid lubricant, which includes FeS bulk, FeS particles and FeS powder, were studied in this article. Their surface morphologies were investigated with SEM, and XRD was used to study the phase structures, TEM was utilized to observe the micro-morphologies and analyze the microstructures. The results showed that the crystals of solid FeS were composed of many hexagonal single crystals and multi-crystals, with two kinds of crystalline structure, hexagonal structure and face-centered cubic structure. The surface of FeS was in the shape of a floccule except for a little granular figure. The micro-morphology of FeS presented irregular flakes which can be seen from TEM pictures, the size of grains ranging between 0.1 μm and 3 μm.

Ni/nano-Al 2 O 3 composite coating was fabricated by automatic brush-plating technique and manually plated Ni/nano-Al 2 O 3 composite coating was also prepared as a comparison. The surface morphology, microstructure, microhardness and wear resistance performance of the coatings were investigated. The results showed that the automatically plated Ni/nano-Al 2 O 3 composite coating possessed smoother, finer, denser microstructure and more uniform performance as compared to the manually plated Ni/nano-Al 2 O 3 composite coating. The former exhibited higher microhardness and better wear resistance under lubricant condition compared with that of the latter. The results presented herein lay the groundwork for future systematical studies in producing nanocomposite coating by brush-plating technique in order to optimize mechanical and tribological properties.

As a new spraying technology used in the remanufacturing engineering, electro-thermal explosion plasma spraying technique holds a lot of advantages. Three kinds of FeAl-base plasma spraying coatings, FeAl, FeCrAl and FeCrAlRE coatings, were prepared by using instantaneous high-energy shock wave effect produced by the electro-thermal explosion of metal conductor alloy foil of FeAl base. Nano-structure and micro-structure especially a metallurgy binding layer with FeAl-base body are formed. It is shown that microstructures of the FeCrAl and FeCrAlRE coatings were greatly improved due to the addition of Cr and RE. Meanwhile corrosion changing laws of these three plasma spray coatings can be gained after anti-corrosion tests under the conditions of high temperature and then sequentially select better electro-thermal explosion plasma spray coating of anti-corrosion and heat resistance.