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A Cr 0.50 Al 0.50 N coating has been prepared by a reactive-magnetronsputtering method on alloy K38G. The coating possesses mainly the B1 type with a small amount of B4-type crystal structure phase. Isothermal oxidation tests were performed at 900-1,100°C for 20 h by thermogravimetric analysis (TGA) in air. The results reveal that the coated samples have much lower mass gain than that of the bare alloy. The parabolic rate constants of the coated samples decrease by 2 orders of magnitude compared with the bare alloy at 1,000 and 1,100°C. During the oxidation of the coated samples below 1,000°C, the main oxide is Cr 2 O 3 , but above 1,000°C, the scale changes to a-Al 2 O 3 . The observed oxidation behaviors demonstrate that the Cr 0.50 Al 0.50 N coating can provide good protection against corrosion over a wide temperature range.

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