| Wear is one of the main failure forms of metal structural materials.The premature failure of metal structural materials due to wear not only brings about the increase of production cost and the waste of metal resources,but also brings serious safety risks to the safe service behavior of metal structural parts.A second phase with special properties or excellent comprehensive properties is added to the metal matrix to form a metal matrix composite coating.This makes up for some performance shortcomings of the metal matrix,improves the performance of the metal matrix "compromise" phenomenon,to avoid premature loss of the base metal.Finally,the comprehensive performance of metal materials is improved and important natural resources are saved.As a result,the prepared metal matrix composite coating has the advantages of high strength,high modulus,excellent resistance to abrasion and oxidation,low coefficient of thermal expansion,etc.,which extends the application of metal materials in related fields.In this paper,Ni-based composite coating as a typical representative of the wear resistance coating system was prepared by plasma cladding technology.Ni-based alloy powder system with TiC?(Tix,Nb1-x)C?NbC as the reinforcing phase was designed.The influences of different Ti/Nb atomic ratio,different mass fraction of the reinforcing phase,and post-heat treatment on its microstructure evolution and frictional wear performance were studied.XRD?SEM?TEM?Vickers microhardness tester?multifunctional wear tester?3D profilometer and other techniques were used to characterize the microstructure and friction-wear properties of the Ni-based composite coating.The effects of aforementioned factors on the evolution of microstructure and tribological properties of Ni-based composite coatings were investigated in detail.The ability of multiple carbides and post heat treatment to refine microstructure,regulate and enhance phase space configuration,balance the strength and toughness,and enhance the wear resistance of coatings were investigated.This paper tries to reveal the internal correlation mechanism of‘enhanced phase space configuration-strength toughness-wear performance'.This paper aims to further develop a system of metal-based tough and wear-resistant coatings for strengthening key high-value components.Scanning Electron Microscope(SEM),X-ray diffraction(XRD)and transmission electron microscopy(TEM)were used to characterize the microstructure and phase of the coating.The results show that the(Ti,Nb)C reinforced Ni-based alloy coating prepared via plasma cladding on the surface of mild steel Q235 has good formability,and the microstructure of the coating is dense and uniform.The coating phase consists of MC(M:Ti,Nb),y-(Ni,Fe)and M23C6.When Ti:Nb=10:0,5:5 and 3:7,the three phases(Ti,Nb)C,y-(Ni,Fe)and M23C6 in the coating exhibit the spatial configuration of random independent distribution behavior.When Ti:Nb=3:7,the length-diameter ratio of Cr-rich M23C6 decreases significantly,showing thinning behavior.When Ti:Nb=0:10,the three phases of NbC,?-(Ni,Fe)and M23C6 in the coating show a distribution space configuration that bridges each other,and the eutectic structure connects NbC geometry particles and M23C6.After the heat treatment at 600?,the microstructure and phase of the coating did not change significantly.However,after the heat treatment at 800?,the microstructure of the five groups of coatings showed a certain behavior of instability and growth.More importantly,the supersaturated solid solution y-(Ni,Fe)precipitated a large number of(Fe,Cr)nanometer precipitation phase,and(Fe,Cr)nanometer precipitation phase had a clean interface with y-(Ni,Fe).The microhardness,wear resistance and fracture behavior of the coating were studied via Vickers microhardness tester?multifunctional wear tester?3D morphometer and SEM.The results showed that with the change of Ti/Nb atomic ratio,the microhardness of the five groups of coatings showed non-monotonic changes between 407HV0.5 and 595HV0.5.The friction coefficient and wear rate of coating also show significant differences,among which the maximum wear rate difference is about 5 times.Compared with the original coatings without heat treatment,the microhardness of the five groups of coatings after heat treatment at 800?fluctuated within the range of 100HV0.2.The wear rate of the coatings also showed significant differences.Compared with the original coatings without heat treatment,the wear rate of the five groups of coatings after heat treatment at 800? decreased.In addition,heat treatment has a significant impact on the fracture behavior of the coating.The fracture of the coating without heat treatment is composed of a large number of step-like morphology and there are penetrating cracks,showing a quasi-cleavage fracture pattern.After heat treatment at 800??a large number of dimples appeared in the fracture morphology of the coating,showing ductile fracture mode.On the basis of the above research contents,high quality TiC?(Tix,Nb1-x)C?NbC Ni-based alloy coating was prepared by plasma cladding technology.The experimental results show that the microstructure,friction coefficient and wear rate of five groups of coatings with high quality enhancement phase fraction still show significant evolution behavior with the change of Ti/Nb atom ratio.The coating phase is composed of(Ti,Nb)C,?-(Ni,Fe)and M23C6.When Ti:Nb=3:7 and 5:5,the eutectic structure is connected with(Tix,Nb1-x)C geometry particles and M23C6,which show lower friction coefficient and wear rate.However,the fracture morphology of the coating showed a quasi-cleavage fracture pattern. |
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