Development of multilayer oxidation resistant coatings on Cr–50Nb alloy.

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]