Heat treatment effect on the microstructure and corrosion behavior of 316L stainless steel fabricated by selective laser melting for proton exchange membrane fuel cells

Microstructure and corrosion behavior of 316L stainless steel fabricated by selective laser melting (SLM) for bipolar plate were investigated and the subsequent heat treatment effect was also clarified. Results showed that sub-grains widely existed in the SLM 316L and the dislocations in the grain boundary migrated and disappeared after heat treatment. The as produced SLM 316L exhibited inferior corrosion resistance than the wrought in 0.5 M H2SO4 solution with 50 ppm Cl- and 2 ppm F- ions at 70 degrees C due to the SLM defects (molten pool boundaries, non-equilibrium phases etc.), and short, stress relief annealing did not homogenize the non-uniform structures. However, recrystallization heat treatment can improve the durability due to the more uniform structure and thicker passive film. Meanwhile, the proportion of the oxides in passive film formed on SLM 316L increased after heat treatment, especially for the chromic oxide, leading to a better anti-corrosive property. (C) 2018 Elsevier Ltd. All rights reserved.