17％Cr添加フェライト系ステンレス鋼の耐酸化性に及ぼすCu，Ni添加および浸炭性雰囲気の影響

抄録

Stainless steel is used as a heat-resistant material not only in air, but also in carburizing atmospheres containing CO and CO₂. Carburization may cause austenization for ferritic stainless steels. In this study, the high-temperature oxidation behaviors of 17％ Cr ferritic stainless steels with and without the addition of austenite-forming elements, such as Cu and Ni, in a carburizing atmosphere at 1123 K were investigated. The steels did not exhibit breakaway oxidation in the temperature range of 1123-1273 K in air. However, doping the steels with Cu and Ni enhanced breakaway oxidation in a carburizing atmosphere at 1123 K. Traces of austenization and carburization were observed at the base metal under the breakaway oxidation scale of the 17％ Cr steel doped with 1％ Cu and 1％ Ni. Thus, it is proposed that the breakaway oxidation of the ferritic stainless steels in a carburizing atmosphere is attributed to austenization induced by carburization and doping with austenite-forming elements.

Fig. 9　Micro-structures of 1Cu-1Ni steels oxidized at 1123 K for 720 ks in air and at 1123 K for 360 ks in a carburizing atmosphere.