Integrated effects of non-equilibrium microstructures on stress corrosion cracking susceptibility of post-treated laser powder-bed-fusion 316 L stainless steels

Abstract

Laser powder-bed-fusion (L-PBF) technique offers unparalleled advantages in fabricating complex geometries for the nuclear industry, while dominant microstructure features responsible for stress corrosion cracking (SCC) remain poorly understood for L-PBFed stainless steels (SSs). This work aims to untangle the integrated effects of non-equilibrium microstructure on SCC behavior of multiple post-treated L-PBFed 316 L SSs in high-temperature oxygenated water. Results unveil that the residual strain and anisotropy grains jointly deteriorate the planar SCC initiation response, while high-density low angle grain boundaries alleviate the depth attack of short-term SCC propagation. Furthermore, the cellular structure, decorated with Cr segregation and dislocation tangles, inhibits the short-term SCC propagation by enhancing the re-passivation capacity and oxide rupture resistance at the crack tip. The other concomitant factors, such as oxide precipitates and melting pools, are considered subordinate to the SCC susceptibility. These insights advance our understanding for optimizing post-heating parameters to enhance the structural integrity of L-PBFed SSs for the application in nuclear power plants.