Study On Microstructure And Wear Properties Of The Deformed TC4 Alloy Treated By 500? Plasma Nitriding And Ageing

Ti6A14V (TC4) alloy after surface modification can improve the wear resistance, and nitriding are economical and practical processing methods for TC4 to obtain stable surface hardening layer. Nitriding TC4 alloy should be carried out at high temperatures (over 800?),therefore more hydrogen and oxygen will be imported inevitably. This study attempts to realize titanium alloy surface nitriding at low temperature and to reduce the content of hydrogen and oxygen through cold rolling treatment in advance.The toughness of TC4 alloy was improved by prior solution treatment, and then cold rolling was carried out at room temperature, finally plasma nitriding was carried out at 500? for different time. The microstructure and phase structure of samples were represented by OM, SEM, XRD techniques. And the mechanical properties were tested by vickers microhardness tester and pin-on-disc friction wear testing machine.The experimental results show that after 500? plasma nitriding, the macroscopic surface of samples are golden. From micro view, many white particles are irregularly distributed on the surface. With the increase of the deformation or nitriding time, the particles amount increases and the size becomes bigger gradually, after that the amount and size reduce.The hardness of aging specimen is 90?140HV higher than that of untreated state, a certain range of deformation slightly influence the friction coefficient curve. The friction coefficient decreases little and then tends to be stable as time prolonging. Its wear mechanism is adhesive wear. The hardness of nitriding specimen is 270-520HV higher than that of original sample.Larger the deformation, higher surface hardness. And the friction coefficient and wear extent reduce slightly. As time prolong, the surface hardness and friction coefficient fall slightly after rise first. Its wear mechanism is abrasive wear, and the wear rate is lower than that of ageing samples. After nitriding cross section of specimen generate Ti3N 1.29, TiN0.3 and trace amount of intermetallic compound AlTi3. Sectional hardness is also much higher than the original hardness. After ageing, internal organization is consisted of lath martensite ?',globular ?-Ti and metastable ?-Ti. With deformation increasing, the crystal length and the second phase precipitation increase. With time extending, the a-Ti phase distribution dispersive but not obvious.Analysis shows that the deformation defects provide diffusion channels for N atomic, so the nitriding at low temperature can be achieved. Nitrides are generated on the surface and intermetallic phase generated inside. Cross section structure are with gradient distribution of hardness. Nitriding treatment lower friction coefficient of TC4 and improve its wear performance.