| Titanium alloys with high specific strength,low density,corrosion resistance and good biocompatibility have been widely used in aerospace,petrochemical,Marine,medical equipment and other fields.However,due to the lack of friction,wear and high temperature oxidation properties of titanium alloy,its use as a key component is restricted.It is a feasible method to prepare the coating with good wear resistance and high temperature oxidation resistance on the surface of titanium alloy by surface modification technology.Laser cladding is one of the effective ways to improve the surface defects of parts in many surface modification technologies because of the metallurgical bonding between the coating and the substrate,the compact structure of the cladding layer and the adjustable coating thickness.In this paper,the composite coating reinforced by nano-sic particles was prepared on the surface of TC4 titanium alloy by laser cladding technology.The microstructure,composition and phase composition of the composite coating were characterized by optical microscope(OM),scanning electron microscope(SEM),energy spectrometer(EDS)and X-ray diffraction(XRD).The microhardness of the composite coating was measured by microhardness tester.The wear properties of composite coatings were tested and the wear mechanism was analyzed.The oxidation resistance of composite coating at high temperature under cyclic oxidation condition was tested by tube furnace and the oxidation mechanism was analyzed.Through the above experiments and tests,the following conclusions can be drawn:The comprehensive properties of the coating prepared by Ti-Al mechanical mixed powder were better than those prepared by alloy powder.Ti-Al+SiC composite coating prepared by adding 0.6%,0.9%,1.2%(wt.%)nano-sic powder is mainly composed of Al Ti3,Al Ti,Ti5Si3,Ti C,Al2O3 and other phases.The phase of Ti-Al+SiC+Ni composite coating prepared by adding 0.6%and 0.9%(wt.%)nano-sic powder included Al Ti3,Al Ti,Ti5Si3,Ti C,Al Ni,Ni Ti,Al2O3.In this study,the Ti-Al+SiC composite coating was prepared by adding 0.6%,0.9%,1.2%(wt.%)nano-sic powder,and the phase of the composite coating was mainly composed of Al Ti3,Al Ti,Ti5Si3,Ti C,Al2O3.Nano-Sic powder of 0.6%and0.9%(wt.%)was added to prepare Ti-Al+SiC+Ni composite coating.The phase of composite coating was mainly composed of Al Ti3,Al Ti,Ti5Si3,Ti C,Al Ni,Ni Ti and Al2O3.The microhardness of the cladding layer is higher than that of TC4 titanium alloy.The wear resistance of Ti-Al+SiC composite coating was improved compared with TC4 titanium alloy,among which the composite coating with added SiC powder of1.2wt.%had the best wear resistance(wear volume:4.5×10-3 mm3).The wear resistance of Ti-Al+SiC+Ni composite coating was 1.64 and 2.47 times higher than that of TC4 titanium alloy(wear volume:9.4×10-3mm3).The improvement of wear resistance of composite coating is due to the addition of SiC to generate hard phases such as Ti C,Al2O3 and Ti5Si3 dispersed in the coating.However,due to coating roughness and easy adhesion wear with GCr15 steel ball,the friction coefficient of coating is higher than that of matrix.Compared with TC4 titanium alloy,the oxidation resistance of Ti-Al+SiC composite coating can be improved by 10?14 times.The oxidation resistance of Ti-Al+SiC+Ni composite coating was 5.22 times and 5.88 times higher than that of TC4 titanium alloy.It was analyzed that the anti-oxidation performance of the composite coating was improved because Al2O3,Si O2 phases were generated in the oxide layer,and the oxide layer had fine structure,thin thickness and good adhesion,which could effectively prevent oxygen diffusion into the coating. |
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