Microstructure and tribological behaviors of Ti6Al4V alloy treated by plasma Ni alloying

Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique. Surface morphology, micro-structure, composition distribution, phase structure, and microhardness of the Ni modified layer were analyzed. Tribological performance of the Ni modified layer and Ti6Al4V substrate was investigated by using pin-on-disc tribometer. The results indicate that roughness of the Ni modified layer was increased due to formation of the micro-convex on the modified surface. The concentration of Ni gradually decreased from the surface to interior. The maximum content of Ni atoms was nearly 90%. The modified layer was composed of TiNi, Ti2Ni and Ti phases. The maximum microhardness of the Ni modified layer was about 677 HV_0.025 which was increased about two-fold of microhardness of the control Ti6Al4V substrate. Wear resistance of the Ni modified layer was improved obviously, and showed micro-abrasion wearing. The strengthened mechanism of the as-treated Ti6Al4V alloy is discussed.