Dislocation driven evolution of passivity in L-PBF 316 L: Unveiling the impact of thermal exposure

This study investigates the influence of subcritical thermal exposure on the passivation behaviour of laser powder bed fusion (L-PBF) processed 316 L stainless steel, with a focus on dislocation-driven mechanisms under industrially relevant conditions. A novel approach was taken by systematically examining the evolution of corrosion resistance as a function of both residual stress and dislocation density across a temperature range of 100–400 °C. The methodology integrated electrochemical characterisation with microstructural and crystallographic analysis. Results revealed a progressive decline in passive film stability up to 300 °C, corresponding with reduced dislocation density and stress relaxation. However, at 400 °C, passive film performance improved significantly despite further residual stress reduction. This behaviour was linked to the start of microstructural recovery, dissolution of subgrain boundaries, and a redistribution of geometrically necessary dislocations. • At 400 °C passivity improves, reversing the degradation trend. • Recovery in passivation is linked to GNDs, rather than residual stress magnitude. • At 400 °C, subgrain boundary redistribution occurred, without recrystallisation. • Shift in dislocation distribution from melt pool boundaries to subgrains at 400 °C. • dislocation density is the dominant factor governing passivity in L-PBF 316L.