Si-modified aluminide coatings deposited on Ti46Al7Nb alloy by slurry method

Ti46Al7Nb alloy has been used as the research substrate material for the deposition of water-based slurries containing Al and Si powders. The diffusion treatment has been carried out at 950 °C for 4 h in Ar atmosphere. The structure of the silicon-modified aluminide coatings 40 μm thick is as follows: (a) an outer zone consisting of TiAl3 phase and titanium silicides formed on the matrix grain boundaries composed of TiAl3–type Ti5Si3; (b) a middle zone containing the same phase components with the matrix TiAl3 and the silicides Ti5Si3, which formed columnar grains; (c) an inner zone, 2 μm thick, consisting of TiAl2 phase. Cyclic oxidation tests were conducted in 30 cycles (690 h at high temperature) and showed a remarkably higher oxidation resistance of the Ti46Al7Nb alloy with the protective coating in comparison with the uncoated sample.