Microstructure and oxidation behavior of Si-MoSi2 coating deposited on Mo substrate at 600 °C and 900 °C in static air

Si-MoSi2 oxidation protective coating was produced on Mo surface by hot dip silicon-plating (HDS) technology. The isothermal oxidation behavior of Si-MoSi2 coating was investigated in air at at 600 degrees C and 900 degrees C. The results indicate that the coating consists of Mo5Si3 interface layer, MoSi2 intermediate layer and Si outer layer. The coating surface is smooth and compact, and the average surface roughness (RSa) is only 0.275 mu m. The oxidation test results show that the thickness of oxide layer of the coating increases to 17-20 mu m, and the weight gain (Delta m/S) of the coating is 3.48 mg/cm(2) after exposed at 600 degrees C for 150 h. After oxidation at 900 degrees C for 40 h, the Delta m/S and oxide layer thicknesses are only 0.085 mg/cm(2) and 6 mu m, respectively. The excellent low-temperature oxidation resistance of Si-MoSi2 coating is mainly attributed to its uniform composition, compact structure, high surface silicon content and extremely low surface roughness.