Abstract
Aluminising of thermal sprayed TiAl-based alloys (49.1 at-% Al) was conducted by a two-step diffusion treatment at 700°C and 1100°C. The coating morphology is strongly dependent on the diffusion temperature; a poreless and thicker TiAl3 layer is obtained at a temperature of 700°C, while the intermediate layer predominantly grows at a temperature of 1100°C. In addition, the second diffusion treatment at 1100°C can also decrease the overall pore volume in the TiAl3 layer. In a cyclic oxidation test at 900°C in the air, TiO2 scale predominantly grows in pores and cracks that occur in the coating, and this promotes the oxidation. It is demonstrated that the two-step diffusion treatment improves the oxidation resistance of aluminide coating on TiAl-based alloys because of the formation of poreless TiAl3 and the crack suppression by the intermediate layer.
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