Implication of nano-scale grain refinement by severe shot peening on corrosion resistance of additively manufactured 316 L stainless steel

Abstract

Microstructural analysis and electrochemical measurements were performed in a SLM 316 L steel that was submitted to SSP. In comparison to the wrought steel, the greatly smaller grain size and higher dislocation density promote nucleation sites for oxidation, and a thicker passive layer, with more stable Cr2O3 oxides, is formed on the SLM steel. SSP produces a thick-gradient surface layer with a nanostructured surface. Overall corrosion resistance decreased in comparison to the un-peened SLM. SSP induces decohesion along the MPBs, leading to pitting. High-residual stresses, twins and dislocation break the cellular-walls, promoting the imperfect cell-structure and jeopardizing the passive film stability.