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

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 Cr 2 O 3 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. • CSP and SSP induce thick gradient structure from surface to the core • SSP promotes the formation of nanograins ( ~ 50 nm) in the upper layer • Corrosion resistance increases in the SLM as-built series • Passive film stability decreases after the SSP treatment • SSP leds to an imperfect cell structure