準安定オーステナイトステレレス鋼の表層組織に及ぼすドライアイスピーニングの影響

抄録

Effect of dry-ice peening on the development of surface microstructure of metastable austenitic stainless steels SUS304 was investigated. Directed spraying of dry-ice particles was emitted on the surface of SUS304 sheets for one and three hours. The surface was cooled and deformed plastically by kinetic energy of dry-ice particles. It was found that deformation-induced martensite (DIM) was formed on the surface, and the area fraction of DIM increased with increasing peening time. Namely, DIM was scattered after 1 hour and was formed uniformly with a thickness of 200μm after 3 hours. Hardness increased at the surface and decreased with a distance from the surface. It was reported in the literature that reverse transformation of DIM by annealing at an appropriate temperature leads to nanocrystalline structure. Therefore, it is applicable to form the surface nanocrystalline structure in metastable austenitic stainless steels by dry-ice peening followed by annealing.