| Titanium alloys are widely used in the fields of aerospace,shipbuilding,biomedicine and energy and chemical industries,but the shortcomings of titanium alloys such as low hardness and poor wear resistance limit its development space.This article first uses plasma nitriding technology to treat TC4 titanium alloy,and then uses multi-arc ion plating to deposit CrAlN,CrAlSiN and TaC coatings on the surface of TC4 titanium alloy,the surface of the nitride layer and the monocrystalline silicon.X-ray diffraction analyzer(XRD),scanning electron microscope(SEM),energy spectrometer(EDS),micro Vickers hardness tester,reciprocating friction experiment and electrochemical corrosion experiments were used to study the TC4 titanium alloy matrix and nitride layer And the phase,surface morphology,hardness,friction and wear and electrochemical corrosion properties of the three coatings.The main conclusions are as follows:(1)There are some micropores and larger particles on the surface of TC4 titanium alloy substrate and nitride layer,but the surface quality of the coating is good.By EDS,C,Si and Ta elements were found on the surface of silicon-based TAC coating.This is because the substrate monocrystalline silicon reacts with the target material to generate Si3TA5 phase,and the coating also contains TAC phase and amorphous carbon structure.The thickness of silicon TAC coating is 285 nm.Si-based Cralsin coating is mainly composed of four elements:N,Si,Al and Cr.The main phases of Cralsin coating are Al N,Cr N,Cr2 N and Al Cr2 phases.The thickness of silicon based Cralsin coating is 707 nm.(2)It is found that the surface hardness of TC4 titanium alloy can be improved by either nitriding treatment or deposition coating.The hardness of the Cralsin coating deposited on the nitride layer is the highest,reaching 3222 Hv0.025,which is about 9 times higher than that of the substrate(325 Hv0.025)and more than 2 times higher than that of the nitride layer(991 Hv0.025).The main reason is that the nitride layer improves the support force of the substrate on the Cralsin coating,and there is hard nitride in the coating.The addition of Si element plays the role of fine grain strengthening and solid solution strengthening.(3)Because the CrAlSiN coating deposited on the nitride layer has extremely high hardness,its wear resistance is the best,the wear scar is very shallow,there is no very clear outline,and the average friction coefficient is 0.22;the wear of the TaC coating The traces are also very shallow,and only a few scratches can be observed.The average friction coefficient of the TaC coating deposited on the nitride layer is only 0.039,mainly because the amorphous carbon in the coating has a self-lubricating effect.(4)Through the electrochemical corrosion test,it is found that the corrosion resistance of the substrate can be improved after the coating is deposited,especially the composite treatment of plasma nitriding and deposition coating can significantly improve the corrosion resistance of the substrate.Due to the presence of defects such as micropores and large particles on the coating surface,the corrosion solution will penetrate into the coating through these defects to cause corrosion,but the coating surface will form a passivation film in a very short time to prevent further penetration of the corrosion solution,which further improves Corrosion resistance of the coating. |
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