Micromorphology evolution, growth mechanism, and oxidation behaviour of the silicon-rich MoSi2 coating at 1200 °C in air

Abstract

The silicon-rich MoSi2 coating with a submicron surface roughness is deposited on Mo substrate by the hot-dip silicon (HDS) plating process. The microstructure, phase composition, and growth mechanism of the silicon-rich MoSi2 coating are characterized. The oxidation kinetics and oxidation mechanism of the coated samples and bare Mo at 1200 °C are also analyzed and compared. The results indicate that the silicon-rich MoSi2 coating is comprised of Si outermost layer, MoSi2 intermediate layer and Mo5Si3 interface layer. The coating has a high surface silicon concentration and a dense structure, and the average surface roughness (RSa) is only 0.248 μm. After exposed at 1200 °C for 20 h, the per unit area weight change rate (Mc) of the coating is only 0.183 mg/cm2 and the thickness of oxide layer is 6.72 μm. The smooth surface, compact structure and excellent self-healing ability of the silicon-rich coating ensure its outstanding antioxidant.