Preparation of TiAl–Cr surface alloy by plasma-surface alloying technique

Abstract A plasma-surface technique was used to form a TiAl–Cr alloy on the surface of a TiAl-based alloy. The feasibility of the alloying process was evaluated by a first principle calculation method. The preparation process was optimized by investigating the effects of processing temperature and discharge pressure on the formation of surface alloy. The calculation using the first-principle method showed that the addition of Cr into the TiAl lattice would increase the stability of the system, and improve mechanical properties of the alloy. The processing temperature was selected at 1100 °C, slightly below the eutectic temperature of the Ti–Al system, ensuring diffusion efficiency and also avoiding the degradation of substrate microstructure. The optimum discharge pressure was 25 Pa within the range of 12–55 Pa. Sputtering and diffusion were well coordinated at this pressure and the obtained alloyed layer had the largest thickness.