Microstructure evolution and corrosion behavior of laser metal deposited 316L stainless steel bipolar plates subjected to tensile deformation

The impact of tensile deformation on the microstructural characteristics and corrosion resistance of 316L austenitic stainless steel (ASS) produced via laser metal deposition (LMD) was systematically studied using electron backscatter diffraction (EBSD) and electrochemical analyses performed in a simulated cathodic environment representative of proton exchange membrane fuel cells (PEMFCs). The findings revealed that the specimen subjected to a 30.0 % pre-strain exhibited the highest corrosion resistance. This improvement was attributed to the synergistic effect of a refined microstructure—marked by an increased fraction of low-angle grain boundaries (LAGBs) and low Σ coincidence site lattice (ΣCSL) boundaries—and the formation of compact passive films, as evidenced by elevated Cr2O3/Cr(OH)3 and O2−/OH− ratios. In contrast, when the pre-strain reached 37.5 %, the corrosion performance deteriorated. Although the quantity of LAGBs and ΣCSL boundaries continued to rise, their positive influence was overshadowed by the formation of excessive α′-martensite, high density of dislocations, and defects within the passive films. These factors collectively compromised the corrosion resistance of LMD-processed 316L ASS under high levels of tensile deformation.

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