オーステナイト系ステンレス鋼の粒界腐食シミュレーション

抄録

Intergranular corrosion of austenitic stainless steel is associated with the Cr depleted zone surrounding Cr carbide precipitated at grain boundary. Computer simulation program of intergranular corrosion, caused by attack of Cr depleted zone, was developed to predict intergranular corrosion susceptibility. Assuming that the formation of Cr depleted zone adjacent to grain boundary is controlled by carbide nucleation rate, thermodynamical property of carbide and Cr diffusion coefficient, two-dimensional redistribution of Cr concentration on grain boundary was calculated by differential method. Induction time of carbide precipitation was calculated by taking account of the effect of C, Cr and Ni content based on the nucleation theory. Calculated corrosion depth in Strauss test coincided well with experimental data in specimens heated at the temperature range of 823 to 1073K and cooled from 1073K. From these results, this computer simulation is found to be able to predict the sensitization of SUS 304 steel heated at the range of 823 to 1073K.