Microstructural evolution and solidification cracking susceptibility of grain boundary engineered fully austenitic stainless steel

Abstract

Solidification cracking has been a serious problem in austenitic stainless steels. Since solidification cracking often occurs at the solidification grain boundary, the grain boundary character distribution (GBCD) in the weld metal may affect the solidification cracking susceptibility. On the other hand, the columnar grains of the weld metal are formed by the epitaxial growth from the grains in the base metal. Therefore, it is expected that microstructure and cracking susceptibility of the weld metal can be reduced by controlling the microstructure of the base metal. In this study, the effect of microstructure of the base metal on the microstructure and solidification cracking susceptibility of the weld metal was examined. The GBCDs of the base metal of the type 310S stainless steel were changed by the thermomechanical process. The solidification cracking susceptibility was evaluated by the Trans-Varestraint test. The thermomechanically processed specimen had larger ratio of coincidence site lattice (CSL) boundaries compared with those of the as-received specimen. Moreover, the specimen was found less susceptible to solidification cracking than was the as-received material. The GBCD analysis indicated that the complex shape and distribution of the grain boundaries in the thermomechanically processed specimen affect the initiation and propagation of solidification cracks.