Oxidation behaviour and microstructure of a dense MoSi2 ceramic coating on Ta substrate prepared using a novel two-step process

Tantalum (Ta) alloys are important ultra-high-temperature structural materials owing to their excellent high-temperature mechanical properties and processability. However, they exhibit poor high-temperature oxidation resistance. In this study, a dense MoSi2 ceramic coating was prepared on a Ta substrate using an innovative multi-arc ion plating process and halide activated pack cementation in order to improve its ultra-high-temperature oxidation resistance. This ceramic coating exhibited a low roughness space arithmetic (287.1 +/- 26.3 nm) and a dense structure. The relationship between the thickness of the coating and the duration of pack-cementation at 1250 degrees C was parabolic. The coating had a service life of more than 12 h at 1750 degrees C, and showed excellent high-temperature oxidation resistance because of the uniform and dense structure of the coating and the rapid formation of a dense SiO2 layer with low O-2 permeability during high-temperature oxidation.