Effect of Al Element on Oxidation Resistance of MoSi₂ Coating

MoSi2 coating and Mo(SiAl)2 coating were prepared on TC4 alloy substrate surface by double cathode glow plasma sputtering technology, and then the coatings were oxidated in air and at 500 ℃ for different times. The effect of Al element on oxidation resistance of MoSi2 coating was studied. The results show that the coatings was composed of diffuse layer of 8 μm thickness and deposition layer of 20 μm thickness, and the coatings were compact and combined with the substrate closely. With the increase of oxidation time, the oxidation mass increase of Mo(SiAl)3 coating was slowly, and lower than that of MoSi2 coating. Lath-like MoO3 was obtained on MoSi2 coating surface after it was oxidated at 500 ℃ for 5 h, and the “PEST” appearing and lots of cracks were found on the coating surface after it was oxidated for 100 h. Al2O3, SiO2 and MnO3 were found on Mo(SiAl)2 coating surface after it was oxidated for 30 h, and its surface was fine and no obvious cracks after oxidation for 100 h. Adding Al element increased the oxidation resistance of MoSi2 coating.