フェライト系ステンレス鋼の粒界腐食感受性と炭化物および窒化物析出の関係(<特集>ステンレス鋼)

概要

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To clarify the cause of intergranular corrosion of 17%Cr ferritic stainless steels, precipitation of chromium carbides and nitrides at grain boundaries was studied by electrical resistivity measurement and electron microscopic observation on the steels having various amounts of carbon and nitrogen. On the quenched and isochronously annealed specimens, precipitation was found at two stages for chromium carbides, (Fe, Cr)_7C_3 at 550°∿650℃ and Cr_<23>C_6 at above 700℃, and also at two stages for chromium nitrides, the one of not identified structure at 400°∿550℃ and Cr_2N at 650°∿750℃. Intergranular corrosion susceptibility was remarkably raised by the precipitation of (Fe, Cr)_7C_3 at 550°∿600℃ and "unknown" nitride at 400°∿550℃. Chromium depletion zone along grain boundaries formed by the very rapid precipitation of these special types of carbide and nitride at the intermediate temperatures around 550℃ was indicated as the most probable reason for intergranular corrosion.
社団法人日本鉄鋼協会の論文
1977-04-01