Insights into the stress corrosion cracking resistance of a selective laser melted 304L stainless steel in high-temperature hydrogenated water

Selective laser melting (SLM) offers unprecedented advantages in manufacturing complex components used in nuclear reactors, and thus has promising application in the nuclear power industry. The compatibility of printed materials with typical reactor coolant should be carefully investigated as the printed materials possess unique microstructure features (e.g. columnar grain, dislocation cell and inclusion) which would inevitably affect the performance. In this work, the stress corrosion cracking (SCC) susceptibility of selective laser melted (SLMed) 304L stainless steel (SS) was evaluated in high-temperature hydrogenated water through slow strain rate tensile test and compared with two wrought 304 SSs. Interestingly, the SLMed 304L SS showed much lower SCC susceptibility than the two wrought 304 SSs, and this finding was mainly ascribed to its optimized composition. From the aspect of corrosion, the intergranular oxidation resistance of SLMed 304L SS is significantly improved due to the reduced contents of Si and Mn. In addition, the high dislocation density in SLMed 304L SS can accelerate the diffusion of solute atoms, thus further enhancing the resistance to intergranular oxidation and promoting the precipitation of oxide inside the crack which barricades the ingress of corrosive media. As for the mechanical aspect, under the combined effects of dislocation cells and nano-oxide inclusions, the SCC initiation can be alleviated as the dislocation motion in the grain matrix is hindered and planar slip is suppressed. Therefore, the optimized chemical composition and printed microstructure render this SLMed 304L SS more resistant to SCC initiation.