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To protect Cr–50Nb alloys from high-temperature oxidation, the Al 2 O 3 /Si–Al multilayer coatings were produced by pack cementation process, followed by sol–gel process and hot pressing. The results indicate that the multilayer coating is dense and exhibits good adherence to the substrate, which consists of a compact Al 2 O 3 outer layer and an inner layer composed of Si, Al, Cr, Nb. Uncoated Cr–50Nb alloy occurs catastrophic oxidation at the initial oxidation stage at 1200 °C. However, the scale spalling resistance of the multilayer coating is improved significantly, and the multilayer coating exhibits good resistance to oxidation. During cyclic oxidation in air at 1200 °C for 100 h, the weight loss is 0.13 mg/cm 2 and the mass gain is 3.38 mg/cm 2 . [ABSTRACT FROM AUTHOR]

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/cm 2 and the mass gain is 6.01 mg/cm 2 . [ABSTRACT FROM AUTHOR]