Effect of vacuum induction heat treatment on the formation of intermetallic compounds between electroplated Ni coating and TC4 alloy

Abstract

In this study, the Ni coated TC4 alloy was treated by vacuum heat treatment to study the effect of induction heat treatment on the diffusion process and the formation of intermetallic compounds at the interface between Ni coating and TC4 substrate to avoid oxidation on the surface. The results by induction heat treatment were compared with that by resistance heat treatment. The effects of heating temperature and heat treatment time of the induction heat treatment were discussed in detail. The formations of intermetallic compounds including TiNi3, TiNi, and Ti2Ni were analyzed. With the increase of heat treatment time, TiNi3 phase is decomposed completely, and the intermetallic compounds at the surface of TC4 alloy are TiNi and Ti2Ni. The Gibbs free energies of intermetallic compounds in Ti-Ni system were calculated, and the eddy current produced by induction heat treatment has an important influence on the formation of intermetallic compounds. The Ni coated TC4 alloy after induction heat treatment for 1050 °C and 60 min shows to have a better tribological property. By conducting induction heat treatment, TiNi phase at surface of TC4 alloy can be obtained which is helpful for further applications of Ti alloy under mechanical contacting conditions.