Residual stress and stress corrosion cracking of austenitic stainless steels in nuclear environments

Abstract

This thesis investigates the potential role of thermal loads promoting stress corrosion cracking in welded type 316L SS austenitic stainless steels in the PWR environments. The representative weld sample of type 316L SS was manufactured from the PWR primary circuit piping segment. Local regions of the weld area were subjected to thermal loading to induce plastic strain and residual stresses. The thermally loaded samples were then exposed to PWR environment in the autoclaves at VTT for a period of one month. Optical and electron microscopic examination was carried out on the samples to observe potential cracks. Furthermore, EBSD analysis was carried out to observe any misorientations between the grains and crystallographic orientation of the weld and base metal. The results did not show any potential cracks in the samples indicating that SS316L can withstand thermal loads and residual stresses in corrosive environments without developing any cracks. Overall, the results demonstrated the susceptibility of type 316L SS and the effect of thermal loading and residual stresses on austenitic stainless steels when exposed to aggressive environments in the nuclear industry.