Friction-wear Characteristics Of Plasma Oxynitriding For TC4 Alloy

Titanium alloys?such as TC4?have been widely used in aerospace,chemical,biomedical and ship fields due to their good biocompatibility,mechanical properties,corrosion resistance and processing properties,as well as their lower price than precious metals.However,due to the low hardness and poor wear resistance of titanium alloy,its further use has been greatly restricted.To seek to improve the poor wear resistance of TC4 alloy,In this study,the surface of TC4 titanium alloy was first nitrided and then nitride-oxygen co-infiltration modified by doubleglow plasma surface alloying technology.The surface topography and grinding crack morphology of modified layer were observed by scanning electron microscope?SEM?,X-ray diffraction?XRD?test modified layer structure,energy spectrometer?EDS?was used to analyze the type and content of modified layer.Nanometer indentation apparatus and automatic scratch apparatus were used to study the nanometer hardness and the bonding strength of the modified layer,and the ball-disk friction and wear test were used to evaluate the wear resistance of the modified layer.The results show that:?1?The influence of working air pressure,nitrogen-oxygen flow ratio,working voltage and heat preservation time on the modified layer are investigated.The optimal process parameters are as follows:source voltage:800V,workpiece voltage:425V,working pressure:35Pa,distance between source electrode and work-piece:15mm,nitrogen oxygen flow ratio:8:1,heat preservation time:3h.?2?The modified layer of TiN and TiO₂ was obtained on the surface of TC4 titanium alloy after nitriding and oxidizing under the optimal process parameters.The total thickness of the seepage layer is 10.2?m and the element content is distributed gradient.The modified layer was composed of deposited and diffused layers.The outer layer is TiO₂ phase,and the nanometer hardness and elastic modulus are 8.7GPa and 181.5GPa,respectively,which are 2.36 times and 1.5 times of the matrix.The surface of the modified layer is smoother and less roughness,and the binding strength between the modified layer and the matrix is about 52.9MPa.?3?Ball-disk friction and wear experiments show that the modified layer can effectively improve the friction and wear resistance of TC4 alloy under different load,speed and friction pair conditions.Compared with the matrix,the friction coefficient and wear area of the modified layer decreased significantly.The main wear mechanism is adhesive wear,abrasive wear and peeling wear.