１２％Ｃｒマルテンサイト系ステンレス鋼の組織と硬さに及ぼす固相窒素吸収処理の影響

概要

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Solution nitriding was applied to conventional 12%Cr stainless steels such as JIS SUS410L, SUS410, SUS420J1 and SUS420J2, and then the microstructure and hardness were examined for the as-quenched specimens as well as tempered ones. Nitrogen concentration was increased to around 0.28 mass% under the solution nitriding condition of 1473K-0.1MPa N<SUB>2</SUB> in all of the 12%Cr steels regardless of the carbon content. Solid solution strengthening by nitrogen was relatively small compared with that by carbon in as-quenched martensite. However, solutionnitrided steels exhibited a remarkably large secondary hardening during tempering, which hardly appears in conventional martensitic stainless steels without nitrogen. TEM observation and X-ray analysis for extracted residue indicated that the secondary hardening by nitrogen was caused by precipitation of fine CrN nitride.