High temperature diffusion behavior between Ta-10W coating and CP-Ti and TC4 alloy

To improve high temperature properties of Titanium alloy, Ta-10W coating was deposited by multi-arc ion plating (MAIP) technique on commercial pure titanium (CP-Ti) and TC4 (Ti-6Al-4V) titanium alloy respectively. The microstructures and high temperature diffusion behavior of Ta-10W coating on CP-Ti and TC4 alloy were investigated by XRD, SEM and EDS. The results showed that the obtained Ta-10W coatings consisted of α-Ta, exhibiting an integrated and compact surface as well as excellent interface bonding. For the Ta-10W/Ti samples, a TiTa solid solution diffusion layer formed and gradually became thicker and thicker over time. After diffusion for 50 h, massive titanium element even diffused to the surface of the coating. During cooling, the β-Ti → α′-Ti martensitic phase transformation occurred, and the martensitic relief morphology appeared on the surface of the coatings. Meanwhile, α-Ta precipitated along the laminate boundary of α-Ti, which leads to the formation of white stripe-like structure in the diffusion layer. Dissimilarity, the Ta-10W/TC4 samples possessed relative high diffusion rate, but the Ti didn't reach the surface of the sample after 50 h. There was a thick diffusion layer which contained two layers formed between Ta-10W and TC4 after heat treatment of 10h, and the Kirkendall voids appeared near the interface of Ta-10W/TC4. This work is helpful to understand the high-temperature performance of refractory coating and provides a new idea for the further study of protective coatings on Titanium alloy.