窒化・酸化・浸炭競合環境における ステンレス鋼製加熱管の減肉機構解明
Wastage mechanism of heating tubes made of austenitic stainless steels in a complex environment of nitriding, oxidizing, and carburizing
著者:
山本 康平 Kohei YAMAMOTO 阿部 博志 Hiroshi ABE 渡邉 豊 Yutaka WATANABE 有岡 真平 Shinpei ARIOKA 小野 雅史 Masashi ONO
発刊日:
公開日:
austenitic stainless steelchemical plantcrystal structurenitridespallingthinning
概要
It was reported that nitride layer formed on SUS310S heating tubes in the reactor of melamine production plant showed severe spalling susceptibility. After replacement to SUS304heating tubes, spalling and thinning was suppressed. According to previous studies, a crystal structure of the nitrided layers of SUS310S and SUS304 heating tubes mainly consist of γ’ and α’, respectively. The reason why the SUS304 heating tube showed low spalling susceptibility was considered to be a smaller expansion rate of α’ compared with γ’. The purpose of this study is to characterize the nitride layer which formed on SUS304 heating tubes by cross sectional observation with optical and magnetic force microscope, and by XRD analysis. As a result, nitrided layer of SUS304 heating tubes consists of thin outer layer and thick inner layer. Outer and inner layers consist of the compound layer (complex of γ’, ε, and ξ) and the diffusion layer (α’) with needlelike γ’ precipitates, respectively. These findings are consistent with the hypothesis that α’ shows low spalling susceptibility in this environment.
