18-8ステンレス鋼の孔食に対する結晶粒界の役割

抄録

The role of grain boundaries in pitting corrosion of 18-8 stainless steels was studied by means of the potentistatic technique, transmission electron microscopic observation and micro-vickers indentation measurements.
The following results were obtained:
(1) Observation results of transmission electron microscopy that pits initiate from the grain boundaries at which chromium carbides are precipitated show that local cells are produced as a result of the accumulation of impurities at grain boundaries, and also that the parts preferentially attacked due to the actions of cells grow into pits.
(2) The fact that pits form on the region of micro-vickers indentations shows that local cells are produced as a result of the presence of regions with weak or broken surface films and the high chemical potential, and also that the parts preferentially attacked due to the actions of cells grow into pits. It seems that such parts correspond to grain boundaries.