Microstructure and oxidation resistance of Cr-Al-Si alloys for high-temperature applications

Abstract

Cr-Al alloys are attracting much attention as heat-and corrosion-resistant coating materials due to their excellent high-temperature properties. In order to investigate the effect of aluminum content on the microstructure and oxidation resistance of Cr-Al-Si alloys, cast specimens were prepared by using a vacuum-arc melting furnace, and high-temperature oxidation tests were conducted with the specimens, for 1 h, at 1100 °C, in air. In the case of cast microstructure of Cr-Al-Si alloys, it consists mainly of Cr single phase, up to 5 at. % Al, and AlCr phases were additionally formed in alloys containing 10% Al or more. In the specimen with 20% Al added, CrSi phase was also found in addition to the AlCr phase. The weight change of the specimens heated for 1 h, at 1100 °C, indicated that all had excellent oxidation resistance. However, when the Al content was less than 10%, the weight gain tended to be a little lower than that of 10% or more.