Microstructure and cyclic oxidation behavior of silicide coating and Si-Al coating on Cr-50Nb alloy

To protect Cr-50Nb alloys from high-temperature oxidation, the silicide diffusion coating and Si-Al coating were produced by pack cementation. The results indicate that the two coatings have three-layer structure and the interfaces are smooth. Uncoated Cr-50Nb alloy occur catastrophic oxidation at the initial oxidation stage at 1200 °C. However, the scale spalling resistance of the two coatings are improved significantly, and Si-Al coating exhibits excellent resistance to oxidation. During cyclic oxidation in air at 1200 °C for 100 h, the weight loss of Si-Al coating is 1.39 mg/cm2 and the mass gain is 6.01 mg/cm2.