The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification proc...The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.展开更多
A good Ti-based joint implant should prevent stress shielding and achieve good bioactivity and anti-infection performance.To meet these requirements,the low-elastic-modulus alloy—Ti–35Nb–2Ta–3Zr—was used as the s...A good Ti-based joint implant should prevent stress shielding and achieve good bioactivity and anti-infection performance.To meet these requirements,the low-elastic-modulus alloy—Ti–35Nb–2Ta–3Zr—was used as the substrate,and functional coatings that contained bioceramics and Ag ions were prepared for coating on TiO_(2)nanotubes(diameter:(80±20)nm and(150±40)nm)using anodization,deposition,and spin-coating methods.The effects of the bioceramics(nano-β-tricalcium phosphate,microhydroxyapatite(micro-HA),and meso-CaSiO_(3))and Ag nanoparticles(size:(50±20)nm)on the antibacterial activity and the tribocorrosion,corrosion,and early in vitro osteogenic behaviors of the nanotubes were investigated.The tribocorrosion and corrosion results showed that the wear rate and corrosive rate were highly dependent on the features of the nanotube surface.Micro-HA showed great wear resistance with a wear rate of(1.26±0.06)×10^(−3)mm^(3)/(N·m)due to adhesive and abrasivewear.Meso-CaSiO_(3)showed enhanced cell adhesion,proliferation,and alkaline phosphatase activity.The coatings that contained nano-Ag exhibited good antibacterial activity with an antibacterial rate of≥89.5%against Escherichia coli.These findings indicate that hybrid coatings may have the potential to accelerate osteogenesis.展开更多
The key components of engineering machinery frequently failed due to working in the high load and high wear operating envir-onment.And the performance of the Fe-based alloy coatings typically employed need to be impro...The key components of engineering machinery frequently failed due to working in the high load and high wear operating envir-onment.And the performance of the Fe-based alloy coatings typically employed need to be improved for fulfilling the service requirements.Herein,a TiC strengthened Fe-based alloy cladding layer,named TiC-Fe coating,was designed and prepared by plasma cladding technology.The frictional wear performance of coating under various loads was tested.The wear morphology of the coating was observed,and its wear mechanism was examined.The results indicated that the TiC-Fe coating was well formed and metallurgically bonded to the Q345C substrate.Its microstructure mainly consisted of Fe-Cr solid solution,α-Fe phase,(Fe,Cr)_(7)C_(3) phase and TiC phase.The coating exhibited an average microhardness of 980 HV0.2,which was about 5.4 times that of the Q345C substrate.The wear mass loss of the TiC-Fe coatings was much smaller than that of the Q345C substrate,which indicated that the wear resistance of the Q345C coating was superior to the substrate,and the wear mechanism of the coating was mainly attributed to the abrasive wear.展开更多
Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powde...Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.展开更多
In order to improve the fire resistance,water resistance and wear resistance of ordinary plywood products in the wood processing industry,three composite structures of plywood products S1,S2 and S3 were designed in th...In order to improve the fire resistance,water resistance and wear resistance of ordinary plywood products in the wood processing industry,three composite structures of plywood products S1,S2 and S3 were designed in this paper,and a reasonable production process was proposed.Through the physical and mechanical properties and fire resistance testing and technical and economic analysis,the applicability of composite plywood was evaluated.The results of the study showed that the physical mechanics of the three kinds of composite structure plywood met the standard requirements,and their fire resistance was far better than that of ordinary plywood.Among them,the S1 structural board had the best overall physical and mechanical properties.The S3 structural board showed the best fire resistance,which was about 1.9 times more than that of ordinary plywood,and the added cost was the lowest.The thin cork board added to the S2 structural board had poor fire performance since the air in the cork board cavities had a certain combustion-supporting effect,which inhibited the fire resistance of high-pressure laminate(HPL)layer.Moreover,the additional cost of the S2 board was the highest,and its comprehensive performance was the worst.The S3 structural plywood product composed of HPL fireproof board with a thickness of about 1 mm in the surface layer and ordinary plywood with a thickness of about 12 mm in the core layer was the most cost-effective product,which could meet the needs of various fields such as construction,home furnishing,decoration and transportation.展开更多
Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some dis...Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.展开更多
TiN-matrix composite coating was prepared on 45# steel by reactive high-velocity oxy-fuel （HVOF） spraying. Its microstructure, phase composition, micro-hardness, corrosion resistance in 3.5% NaC1 solution and wear r...TiN-matrix composite coating was prepared on 45# steel by reactive high-velocity oxy-fuel （HVOF） spraying. Its microstructure, phase composition, micro-hardness, corrosion resistance in 3.5% NaC1 solution and wear resistance were analyzed. The results suggest that the TiN-matrix composite coating is well bonded with the substrate. The micro-hardness measured decreases with the increase of applied test loads. And the micro-hardness of the coating under heavy loads is relatively high. The TiN-matrix composite coating exhibits an excellent corrosion resistance in 3.5% NaC1 solution. The corrosion potential of coating is positive and the passivation zone is broad, which indicates that the TiN-matrix composite coating is stable in the electrolyte and provides excellent protection to the substrate. The wear coefficient of the coating under all loads maintains at 0.49-0.50. The wear mechanism of the coating is revealed to be three-body abrasive wear. Yet the failure forms of TiN-matrix composite coating under different loads have an obvious difference. The failure form of coating under light loads is particle spallation due to the stress concentration while that of coating under heavy loads is crackin~ between inter-lamellae.展开更多
In order to study the effect of element Nb on the microstructure and properties of the biomedical β-type Ti-Mo based alloys,Ti-15Mo-xNb（x=5,10,15 and 20 in %） alloys were investigated.The dry wear resistance of β-...In order to study the effect of element Nb on the microstructure and properties of the biomedical β-type Ti-Mo based alloys,Ti-15Mo-xNb（x=5,10,15 and 20 in %） alloys were investigated.The dry wear resistance of β-type Ti-15Mo-xNb alloys against Gr15 ball was investigated on CJS111A ball-disk wear instrument.Experimental results indicate that crystal structure and morphology of the Ti-15Mo-xNb alloys are sensitive to their Nb contents.Ti-15Mo-xNb alloys match those for β phase peaks and no any phases are found.The Vickers hardness values of all the Ti-15Mo-xNb alloys are higher than HV200.The compression yield strength of the Ti-15Mo-5Nb alloy is the lowest and that of the Ti-15Mo-10Nb alloy is the highest.For all the Ti-15Mo-xNb alloys,the friction coefficient is not constant but takes a higher value.In dry condition,SEM study reveals deep parallel scars on the wear surfaces of all the Ti-15Mo-xNb alloys under different loads.The friction coefficient of the Ti-15Mo-5Nb alloy under 1 N is the lowest.The wear principal mechanism for Ti-15Mo-xNb alloys is adhesive wear.展开更多
In order to improve the wear resistance properties of copper substrate, a layer of electroplated nickel was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack...In order to improve the wear resistance properties of copper substrate, a layer of electroplated nickel was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack cementation process with a slurry pack cementation mixture composed of TiO2 as titanizing source, pure Al powder as aluminzing source and also a reducer for titanizing, an activator of NH4Cl and albumen （egg white） as cohesive agent. The Ti-Al coating was fabricated on the surface of electro-deposited nickel layer on copper matrix followed by the slurry pack cementation process. The effects of slurry pack cementation temperature on the microstructures and wear resistance of Ti-Al coating were studied. The results show that the microstructure of the coating changed from NiAl＋Ni3（Ti,Al） to NiAl ＋Ni3（Ti,Al）＋Ni4Ti3 to Ni4Ti3＋NiAl, and to NiAl＋Ni3（Ti,Al）＋NiTi with slurry pack cementation temperature ranging from 800 ℃ to 950 ℃ in 12 h. The friction coefficient of Ti-Al coating decreased and the hardness increased with increasing the slurry pack cementation temperature. The minimum friction coefficient was 1/3 and the minimum hardness was 5 times larger than that of pure copper.展开更多
The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increa...The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increases the hardness values of the matrix at both room and high temperature and improves the wear resistance of the material.The hardness values and the wear resistance of the composite rise with the increase of the particle volume fraction or the decrease of the particle size.The raising of test temperature results in a rapid descending of its hardness values.However, the addition of Al2O3P improves the property of high temperature resistance of Zn-Al alloys significantly.Moreover,the effect of quenching, tempering or cycling heat treatment on the hardness values of the composite is also studied.展开更多
The welding property of TiB2/ZL101 composite was investigated using electron beam（EB） welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing para...The welding property of TiB2/ZL101 composite was investigated using electron beam（EB） welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing parameters and scanning rate.The reinforcement particles TiB2 distributed homogeneously in welding seam without any segregation.The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal.Wear resistance of welding seam is improved greatly compared with base metal.The results show that the TiB2/ZL101 composite can be successfully welded by EB technology.展开更多
Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector...Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.展开更多
Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼1...Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.展开更多
In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear pe...In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current(DC)reactive magnetron sputtering is investigated.The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings.In general,two layers are formed during the oxidation process:i)Ti(V)O_(2) on top,followed by a protective layer,which is subdivided into two layers,Cr_(2)O_(3) and Si-O.ii)The diffusion of V controls the oxidation of V-containing coatings.The addition of vanadium improves the wear resistance of coatings,and the wear rate decreases with increasing V content in the coatings;however,the friction coefficient is independent of the chemical composition of the coatings.The wear of the V-containing coatings is driven by polishing wear.展开更多
Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-Si...Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE is 7-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. Bui ij the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.展开更多
The wear and corrosion resistance of Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） and Fe_（77.3）Cr_（15.8）Ni_（3.9）Mo_（1.1）Mn_（0.5）C_（0.2）Si_（1.2） coatings laser-cladded on AISI 4...The wear and corrosion resistance of Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） and Fe_（77.3）Cr_（15.8）Ni_（3.9）Mo_（1.1）Mn_（0.5）C_（0.2）Si_（1.2） coatings laser-cladded on AISI 4130 steel were studied.The coatings possess excellent wear and corrosion resistance despite the absence of expensive yttrium,tungsten,and cobalt and very little molybdenum.The microstructure mainly consists of dendrites and eutectic phases,such as duplex（γ＋α）-Fe and the Fe–Cr（Ni）solid solution,confirmed via energy dispersive spectrometry and X-ray diffraction.The cladded Fe-based coatings have lower coefficients of friction,and narrower and shallower wear tracks than the substrate without the cladding,and the main wear mechanism is mild abrasive wear.Electrochemical test results suggest that the soft Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） coating with high Cr and Ni concentrations has high passivation resistance,low corrosion current,and positive corrosion potential,providing a better protective barrier layer to the AISI 4130 steel against corrosion.展开更多
WC-8wt.% Co cemented carbides with varied nano-Al 2 O 3 and nano-ZrO 2 contents were prepared respectively following conventional powder metallurgical procedures. Effects of nano-Al 2 O 3 and nano-ZrO 2 on the microst...WC-8wt.% Co cemented carbides with varied nano-Al 2 O 3 and nano-ZrO 2 contents were prepared respectively following conventional powder metallurgical procedures. Effects of nano-Al 2 O 3 and nano-ZrO 2 on the microstructure, behavior, and abrasive wear resistance were investigated. The result shows that a finer and more homogenous microstructure can be achieved by increasing nano-Al 2 O 3 , and increasing nano-ZrO 2 makes the microstructure more refined. Nano-Al 2 O 3 and nano-ZrO 2 could both help to give increased hardness. Transverse rupture strength is higher if the above nano-oxides are doped appropriately, whereas excess addition is deleterious. Abrasive wear resistance presents different variations with respect to increasing nano-Al 2 O 3 and nano-ZrO 2 . By contrast, increasing nano-ZrO 2 enhances the abrasive wear resistance more effectively than increasing nano-Al 2 O 3 . The influence of the two nano-oxides contents on the abrasive wear resistance does not almost vary with wear time, and the optimum addition level of nano-Al 2 O 3 in WC-8% Co cemented carbide is 0.3 wt.% from the stand of abrasive wear resistance. In addition, both of the nano-oxides can retard the increase of wear rate in long-term abrasive wear.展开更多
High chromium cast iron（HCCI） is taken as material of coal water slurry pump impeller, but it is susceptible to produce serious abrasive wear and erosion wear because of souring of hard coal particles. The research ...High chromium cast iron（HCCI） is taken as material of coal water slurry pump impeller, but it is susceptible to produce serious abrasive wear and erosion wear because of souring of hard coal particles. The research on optimization of heat treatments to improve abrasive wear properties of HCCI is insufficient, so effect of heat treatments on the microstructure, hardness, toughness, and wear resistance of Cr26 HCCI is investigated to determine the optimal heat treatment process for HCCI. A series of heat treatments are employed. The microstructures of HCCI specimens are examined by using optical microscopy and scanning electron microscopy. The hardness and impact fracture toughness of as-cast and heat treated specimens are measured. The wear tests are assessed by a Type M200 ring-on block wear tester. The results show the following： With increase of the quenching temperature from 950 ℃ to 1050 ℃, the hardness of Cr26 HCCI increased to a certain value, kept for a time and then decreased. The optimal heat treatment process is 2 h quenching treatment at 1000 ℃, followed by a subsequent 2 h tempering at 400 ℃. The hardness of HCCI is related to the precipitation and redissolution of secondary carbides in the process of heat treatment. The subsequent tempering treatment would result in a slight decrease of hardness but increase of toughness. The wear resistance is much related to the ＂supporting＂ effect of the matrix and the ＂protective＂ effect of the hard carbide embedded in the matrix, and the wear resistance is further dependent on the hardness and the toughness of the matrix. This research can provide an important insight on developing an optimized heat treatment method to improve the wear resistance of HCCI.展开更多
Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter t...Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.展开更多
Laser cladding nickel-based alloy coating （Ni60） and nickel-based composite coating doped with WC particles by 35 % （WCp/Ni） were produced on the low-carbon steel substrate by CO2 continuous wave laser with power ...Laser cladding nickel-based alloy coating （Ni60） and nickel-based composite coating doped with WC particles by 35 % （WCp/Ni） were produced on the low-carbon steel substrate by CO2 continuous wave laser with power of 5 kW using the injected powder technique. The effect of laser power on microstructure and wear resistance of laser cladding WCp/Ni cermet coating was investigated. The WCp/Ni alloy coating with evenly distributed WC ceramic phases and the better bond with the substrate alloy was obtained at a power of 2.2 kW. Diffusion solution reaction happened between WC particles and the substrate alloy during laser cladding, and led to the formation of block rich-tungsten carbide on the edges of the WC particles, especially at higher power. The WCp/Ni alloy coating consists of the undissolved WC particles, the block or dendritic rich-tungsten carbide, the bar-like rich-chromium carbide, and dendrite solid solution and eutectic structure among the carbides. Microhardness and wear resistance of the WCp/Ni coating at different powers were much higher or better than those of Ni60 alloy coating, and the best results were obtained at power of 2.2 kW.展开更多
基金the National Natural Science Foundation of China(Grant number 51771178)Shaanxi Outstanding Youth Fund project(Grant number 2021JC-45)+2 种基金Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007)the Major Program of Science and Technology in Shaanxi Province(Grant number20191102006)Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019)。
文摘The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.
基金supported by the National Natural Science Foundation of China(Nos.52071346,52111530193,and 52274387)the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(No.2023JJ10075)+3 种基金the Hunan Provincial Natural Science Foundation of China(No.2021JJ30846)the Central South University Research Program of Advanced Interdisciplinary Studies(No.2023QYJC038)the Funding for the Medical Engineering Cross Disciplinary Project at Shanghai Jiao Tong University,and the Fundamental Research Funds for the Central Universities of Central South University(No.2022ZZTS0402)The authors would also thank Sinoma Institute of Materials Research(Guangzhou)Co.,Ltd.for the assistance with the TEM characterization.
文摘A good Ti-based joint implant should prevent stress shielding and achieve good bioactivity and anti-infection performance.To meet these requirements,the low-elastic-modulus alloy—Ti–35Nb–2Ta–3Zr—was used as the substrate,and functional coatings that contained bioceramics and Ag ions were prepared for coating on TiO_(2)nanotubes(diameter:(80±20)nm and(150±40)nm)using anodization,deposition,and spin-coating methods.The effects of the bioceramics(nano-β-tricalcium phosphate,microhydroxyapatite(micro-HA),and meso-CaSiO_(3))and Ag nanoparticles(size:(50±20)nm)on the antibacterial activity and the tribocorrosion,corrosion,and early in vitro osteogenic behaviors of the nanotubes were investigated.The tribocorrosion and corrosion results showed that the wear rate and corrosive rate were highly dependent on the features of the nanotube surface.Micro-HA showed great wear resistance with a wear rate of(1.26±0.06)×10^(−3)mm^(3)/(N·m)due to adhesive and abrasivewear.Meso-CaSiO_(3)showed enhanced cell adhesion,proliferation,and alkaline phosphatase activity.The coatings that contained nano-Ag exhibited good antibacterial activity with an antibacterial rate of≥89.5%against Escherichia coli.These findings indicate that hybrid coatings may have the potential to accelerate osteogenesis.
基金supported by National Natural Science Foundation of China(No.52130509,92166105)the Science and Technology Innovation Program of Hunan Province(No.2021RC3096)145 project and Natural Science Foundation of Hunan Province(No.2023JJ30038).
文摘The key components of engineering machinery frequently failed due to working in the high load and high wear operating envir-onment.And the performance of the Fe-based alloy coatings typically employed need to be improved for fulfilling the service requirements.Herein,a TiC strengthened Fe-based alloy cladding layer,named TiC-Fe coating,was designed and prepared by plasma cladding technology.The frictional wear performance of coating under various loads was tested.The wear morphology of the coating was observed,and its wear mechanism was examined.The results indicated that the TiC-Fe coating was well formed and metallurgically bonded to the Q345C substrate.Its microstructure mainly consisted of Fe-Cr solid solution,α-Fe phase,(Fe,Cr)_(7)C_(3) phase and TiC phase.The coating exhibited an average microhardness of 980 HV0.2,which was about 5.4 times that of the Q345C substrate.The wear mass loss of the TiC-Fe coatings was much smaller than that of the Q345C substrate,which indicated that the wear resistance of the Q345C coating was superior to the substrate,and the wear mechanism of the coating was mainly attributed to the abrasive wear.
基金supported by the National Natural Science Foundation of China (52174299)the Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials, Chongqing University, Chongqing 400044, China。
文摘Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.
基金This work was supported by the 2020 Jiangsu Provincial Department of Science and Technology Policy Guidance Category(North Jiangsu Science and Technology Special SZ-L YG202014).
文摘In order to improve the fire resistance,water resistance and wear resistance of ordinary plywood products in the wood processing industry,three composite structures of plywood products S1,S2 and S3 were designed in this paper,and a reasonable production process was proposed.Through the physical and mechanical properties and fire resistance testing and technical and economic analysis,the applicability of composite plywood was evaluated.The results of the study showed that the physical mechanics of the three kinds of composite structure plywood met the standard requirements,and their fire resistance was far better than that of ordinary plywood.Among them,the S1 structural board had the best overall physical and mechanical properties.The S3 structural board showed the best fire resistance,which was about 1.9 times more than that of ordinary plywood,and the added cost was the lowest.The thin cork board added to the S2 structural board had poor fire performance since the air in the cork board cavities had a certain combustion-supporting effect,which inhibited the fire resistance of high-pressure laminate(HPL)layer.Moreover,the additional cost of the S2 board was the highest,and its comprehensive performance was the worst.The S3 structural plywood product composed of HPL fireproof board with a thickness of about 1 mm in the surface layer and ordinary plywood with a thickness of about 12 mm in the core layer was the most cost-effective product,which could meet the needs of various fields such as construction,home furnishing,decoration and transportation.
基金This work is financially supported by the National Natural Science Foundation of China (No.2992021).
文摘Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.
基金Project(KFJJ10-15M) supported by the Open Fund of State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,ChinaProject(E2013208101) supported by the Nature Science Fund of Hebei Province,China+1 种基金Project(Z2012100) supported by Colleges and Universities Science and Technology Research Fund of Hebei Province,ChinaProject supported by the Outstanding Youth Fund of Hebei University of Science and Technology,China
文摘TiN-matrix composite coating was prepared on 45# steel by reactive high-velocity oxy-fuel （HVOF） spraying. Its microstructure, phase composition, micro-hardness, corrosion resistance in 3.5% NaC1 solution and wear resistance were analyzed. The results suggest that the TiN-matrix composite coating is well bonded with the substrate. The micro-hardness measured decreases with the increase of applied test loads. And the micro-hardness of the coating under heavy loads is relatively high. The TiN-matrix composite coating exhibits an excellent corrosion resistance in 3.5% NaC1 solution. The corrosion potential of coating is positive and the passivation zone is broad, which indicates that the TiN-matrix composite coating is stable in the electrolyte and provides excellent protection to the substrate. The wear coefficient of the coating under all loads maintains at 0.49-0.50. The wear mechanism of the coating is revealed to be three-body abrasive wear. Yet the failure forms of TiN-matrix composite coating under different loads have an obvious difference. The failure form of coating under light loads is particle spallation due to the stress concentration while that of coating under heavy loads is crackin~ between inter-lamellae.
基金Project(20080440850) supported by China Postdoctoral Science FoundationProject(ZJY0605-02) supported by the Natural Science Foundation of Heilongjiang Province,ChinaProject(HIT.NSRIF.2012002) supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to study the effect of element Nb on the microstructure and properties of the biomedical β-type Ti-Mo based alloys,Ti-15Mo-xNb（x=5,10,15 and 20 in %） alloys were investigated.The dry wear resistance of β-type Ti-15Mo-xNb alloys against Gr15 ball was investigated on CJS111A ball-disk wear instrument.Experimental results indicate that crystal structure and morphology of the Ti-15Mo-xNb alloys are sensitive to their Nb contents.Ti-15Mo-xNb alloys match those for β phase peaks and no any phases are found.The Vickers hardness values of all the Ti-15Mo-xNb alloys are higher than HV200.The compression yield strength of the Ti-15Mo-5Nb alloy is the lowest and that of the Ti-15Mo-10Nb alloy is the highest.For all the Ti-15Mo-xNb alloys,the friction coefficient is not constant but takes a higher value.In dry condition,SEM study reveals deep parallel scars on the wear surfaces of all the Ti-15Mo-xNb alloys under different loads.The friction coefficient of the Ti-15Mo-5Nb alloy under 1 N is the lowest.The wear principal mechanism for Ti-15Mo-xNb alloys is adhesive wear.
基金Projects(YKJ201203,CKJB201205)supported by the Nanjing Institute of Technology,China
文摘In order to improve the wear resistance properties of copper substrate, a layer of electroplated nickel was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack cementation process with a slurry pack cementation mixture composed of TiO2 as titanizing source, pure Al powder as aluminzing source and also a reducer for titanizing, an activator of NH4Cl and albumen （egg white） as cohesive agent. The Ti-Al coating was fabricated on the surface of electro-deposited nickel layer on copper matrix followed by the slurry pack cementation process. The effects of slurry pack cementation temperature on the microstructures and wear resistance of Ti-Al coating were studied. The results show that the microstructure of the coating changed from NiAl＋Ni3（Ti,Al） to NiAl ＋Ni3（Ti,Al）＋Ni4Ti3 to Ni4Ti3＋NiAl, and to NiAl＋Ni3（Ti,Al）＋NiTi with slurry pack cementation temperature ranging from 800 ℃ to 950 ℃ in 12 h. The friction coefficient of Ti-Al coating decreased and the hardness increased with increasing the slurry pack cementation temperature. The minimum friction coefficient was 1/3 and the minimum hardness was 5 times larger than that of pure copper.
文摘The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increases the hardness values of the matrix at both room and high temperature and improves the wear resistance of the material.The hardness values and the wear resistance of the composite rise with the increase of the particle volume fraction or the decrease of the particle size.The raising of test temperature results in a rapid descending of its hardness values.However, the addition of Al2O3P improves the property of high temperature resistance of Zn-Al alloys significantly.Moreover,the effect of quenching, tempering or cycling heat treatment on the hardness values of the composite is also studied.
基金Project(11ZR1417500) supported by Natural Science Foundation of Shanghai,China
文摘The welding property of TiB2/ZL101 composite was investigated using electron beam（EB） welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing parameters and scanning rate.The reinforcement particles TiB2 distributed homogeneously in welding seam without any segregation.The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal.Wear resistance of welding seam is improved greatly compared with base metal.The results show that the TiB2/ZL101 composite can be successfully welded by EB technology.
文摘Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.
基金This work was financially supported by the Jiangsu Distinguished Professor Project,the Innovate UK(Project reference:10004694)the National Key R&D Program of China 2021YFB3401200.The Experimental Techniques Centre at Brunel University London and Nanjing University of Aeronautics and Astronautics are acknowledged.The authors also acknowledge the characterization facility at Shanghai Jiao Tong University,Central South University,University of Birmingham and University of Lille.
文摘Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.
基金financially supported by the National Natural Science Foundation of China(Nos.51801081 and 52171071)national funds through FCT of Portugal-Fundacao para a Ciencia e a Tecnologia,under a scientific contract of 2021.04115,CEMMPRE-ref.“UIDB/00285/2020”and LA/P/0112/2020 projects+2 种基金FEDER funds through the COMPETE program-Operational Program on Competitiveness Factorsnational funds through FCT-Foundation for Science and Technology,Outstanding University Young Teachers of“Qing Lan Project”of Jiangsu Province of China,Excellent Talents of“Shenlan Project”of Jiangsu University of Science and Technology of ChinaA part of this study was supported by the Directorate-General of Scientific Research and Technological Development(Algeria)。
文摘In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current(DC)reactive magnetron sputtering is investigated.The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings.In general,two layers are formed during the oxidation process:i)Ti(V)O_(2) on top,followed by a protective layer,which is subdivided into two layers,Cr_(2)O_(3) and Si-O.ii)The diffusion of V controls the oxidation of V-containing coatings.The addition of vanadium improves the wear resistance of coatings,and the wear rate decreases with increasing V content in the coatings;however,the friction coefficient is independent of the chemical composition of the coatings.The wear of the V-containing coatings is driven by polishing wear.
基金The project was supported by Yunnan Provincial Natural Science Foundation (95B11-5).
文摘Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE is 7-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. Bui ij the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.
基金financially supported by the Ocean Public Science and Technology Research Fund Projects of China (No. 201405013-3)the Science & Technology Program of Shanghai Maritime University (No. 20130448)+1 种基金the China Postdoctoral Science Foundation (No. 2017M620153)the National Natural Science Foundation of China (No. 51609133)
文摘The wear and corrosion resistance of Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） and Fe_（77.3）Cr_（15.8）Ni_（3.9）Mo_（1.1）Mn_（0.5）C_（0.2）Si_（1.2） coatings laser-cladded on AISI 4130 steel were studied.The coatings possess excellent wear and corrosion resistance despite the absence of expensive yttrium,tungsten,and cobalt and very little molybdenum.The microstructure mainly consists of dendrites and eutectic phases,such as duplex（γ＋α）-Fe and the Fe–Cr（Ni）solid solution,confirmed via energy dispersive spectrometry and X-ray diffraction.The cladded Fe-based coatings have lower coefficients of friction,and narrower and shallower wear tracks than the substrate without the cladding,and the main wear mechanism is mild abrasive wear.Electrochemical test results suggest that the soft Fe_（72.2）Cr_（16.8）Ni_（7.3）Mo_（1.6）Mn_（0.7）C_（0.2）Si_（1.2） coating with high Cr and Ni concentrations has high passivation resistance,low corrosion current,and positive corrosion potential,providing a better protective barrier layer to the AISI 4130 steel against corrosion.
基金supported by the Science and Technology Projects of Sichuan Province, China (No. 2008GZ0179)
文摘WC-8wt.% Co cemented carbides with varied nano-Al 2 O 3 and nano-ZrO 2 contents were prepared respectively following conventional powder metallurgical procedures. Effects of nano-Al 2 O 3 and nano-ZrO 2 on the microstructure, behavior, and abrasive wear resistance were investigated. The result shows that a finer and more homogenous microstructure can be achieved by increasing nano-Al 2 O 3 , and increasing nano-ZrO 2 makes the microstructure more refined. Nano-Al 2 O 3 and nano-ZrO 2 could both help to give increased hardness. Transverse rupture strength is higher if the above nano-oxides are doped appropriately, whereas excess addition is deleterious. Abrasive wear resistance presents different variations with respect to increasing nano-Al 2 O 3 and nano-ZrO 2 . By contrast, increasing nano-ZrO 2 enhances the abrasive wear resistance more effectively than increasing nano-Al 2 O 3 . The influence of the two nano-oxides contents on the abrasive wear resistance does not almost vary with wear time, and the optimum addition level of nano-Al 2 O 3 in WC-8% Co cemented carbide is 0.3 wt.% from the stand of abrasive wear resistance. In addition, both of the nano-oxides can retard the increase of wear rate in long-term abrasive wear.
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2013BAF01B01)
文摘High chromium cast iron（HCCI） is taken as material of coal water slurry pump impeller, but it is susceptible to produce serious abrasive wear and erosion wear because of souring of hard coal particles. The research on optimization of heat treatments to improve abrasive wear properties of HCCI is insufficient, so effect of heat treatments on the microstructure, hardness, toughness, and wear resistance of Cr26 HCCI is investigated to determine the optimal heat treatment process for HCCI. A series of heat treatments are employed. The microstructures of HCCI specimens are examined by using optical microscopy and scanning electron microscopy. The hardness and impact fracture toughness of as-cast and heat treated specimens are measured. The wear tests are assessed by a Type M200 ring-on block wear tester. The results show the following： With increase of the quenching temperature from 950 ℃ to 1050 ℃, the hardness of Cr26 HCCI increased to a certain value, kept for a time and then decreased. The optimal heat treatment process is 2 h quenching treatment at 1000 ℃, followed by a subsequent 2 h tempering at 400 ℃. The hardness of HCCI is related to the precipitation and redissolution of secondary carbides in the process of heat treatment. The subsequent tempering treatment would result in a slight decrease of hardness but increase of toughness. The wear resistance is much related to the ＂supporting＂ effect of the matrix and the ＂protective＂ effect of the hard carbide embedded in the matrix, and the wear resistance is further dependent on the hardness and the toughness of the matrix. This research can provide an important insight on developing an optimized heat treatment method to improve the wear resistance of HCCI.
基金Financial assistance from Armament Research Board, New Delhi, India
文摘Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.
基金Item Sponsored by Research Programof Anhui Science and Technology Office (2005KJ030) and Korea Research FoundationGrant (KRF-2004-005-D00096)
文摘Laser cladding nickel-based alloy coating （Ni60） and nickel-based composite coating doped with WC particles by 35 % （WCp/Ni） were produced on the low-carbon steel substrate by CO2 continuous wave laser with power of 5 kW using the injected powder technique. The effect of laser power on microstructure and wear resistance of laser cladding WCp/Ni cermet coating was investigated. The WCp/Ni alloy coating with evenly distributed WC ceramic phases and the better bond with the substrate alloy was obtained at a power of 2.2 kW. Diffusion solution reaction happened between WC particles and the substrate alloy during laser cladding, and led to the formation of block rich-tungsten carbide on the edges of the WC particles, especially at higher power. The WCp/Ni alloy coating consists of the undissolved WC particles, the block or dendritic rich-tungsten carbide, the bar-like rich-chromium carbide, and dendrite solid solution and eutectic structure among the carbides. Microhardness and wear resistance of the WCp/Ni coating at different powers were much higher or better than those of Ni60 alloy coating, and the best results were obtained at power of 2.2 kW.
