Microstructure evolution and oxidation behavior of B modified MoSi2 coating on Nb-Si based alloys

Mo-Si-B was coated on Nb-Si based alloys using d-gun spraying of Mo followed by Si and B co-deposition. Microstructure evolution and the oxidation behavior of the coating were studied. The coating consists of a MoSi2 layer with dispersed MoB particles during the initial co-deposition. A continuous MoB layer forms beneath the MoSi2 layer after a prolonging time. The growth rate of the coating follows a parabolic law. The mass gain of Mo-Si-B coating is only 0.92 mg/cm2 after oxidation at 1250 °C for 100 h. The good oxidation resistance results from a protective borosilicate scale formed on the coating.