Surface quality and dimensional tolerances of the selective laser melting (SLM) process are not good enough for many industrial applications and grinding as a common finishing process introduces many surface modifications. Investigation on the effect of grinding induced surface residual stress (RS) on early stages of stress corrosion cracking (SCC) of SLM manufactured 316L austenitic stainless steel was conducted. Potentiodynamic and galvanostatic tests in a 3.5% NaCl aqueous solution, XRD, SEM and energy-dispersive X-ray spectroscopy (EDX) analysis were performed. For annealed and specimens with a low RS magnitude, the dominant observation was pit initiation from existing pores and growth in the build direction. For specimens with medium RS level, SCC initiation from pore sites and propagation along melt pool boundaries and for specimens with the highest detected RS, crack initiation from melt pool boundaries, grains, machining marks, and pore sites were observed. Cracks propagated in different directions, i.e., along melt pool boundaries, near-surface transgranular, and transgranular through columnar microstructure. Galvanostatic tests showed three distinctive regions that corresponded to crack and pit initiation and growth. The synergistic effect of high dislocation density along melt pool boundaries, stress concentration in pore sites, molybdenum segregation, and surface RS was the cause of SCC susceptibility of specimens with high RS magnitude.

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Experimental investigation on the relation of grinding induced surface residual stresses (RS) with stress corrosion cracking (SCC) susceptibility and electrochemical behaviour was conducted on 316L austenitic stainless steel in 3.5% sodium chloride aqueous solution. Grinding was done with the same process parameters to lower the effect of other known parameters on SCC initiation. The corrosion behaviour was characterised by Potentiodynamic and galvanostatic tests. The latest was performed under fixed current density in metastable region. There was a strong relationship between the electrochemical results with RS magnitude. Microscopic investigation showed that the RS induced by grinding could not be the reason for SCC and the dominant defect observed was pitting for all the specimens. The time needed for the breakdown of the passive layer was exponentially related to RS level but the propagation of pits was nearly the same for all the specimens.