Microstructure and oxidation behavior of Si-MoSi2 functionally graded coating on Mo substrate

The Si-MoSi2 functionally graded coating on Mo substrate consisting of a Si-MoSi2 layer (2.5 µm), a MoSi2 layer (18 µm) and a Mo-Mo5Si3-Mo3Si layer (2-4 µm) was prepared by a liquid phase siliconizing method. The siliconized coating has a dense layered structure and no micro-cracks and holes. The Si element mainly enriches on the surface with the highest content of about 50 wt%, and inhibits the formation of Mo5Si3 and volatile MoO3 and improves the high-temperature oxidation resistance of the coating. The mass gain of Si-MoSi2 coating is only 0.17 wt% after oxidized at 1600 ℃ for 70 h. The Si-MoSi2 functionally graded coating exhibits better high temperature oxidation resistance than pure MoSi2 coating.