The influence of active screen plasma nitriding temperature on the microstructure and properties of LPBF-processed 316 L stainless steel fuel cell bipolar plates

Laser powder bed fusion (LPBF) technology, with advantages including high forming freedom, short preparation cycle, and significant cost-effectiveness, has successfully demonstrated its viability in the production of metal bipolar plates (BPPs) for fuel cells. However, LPBF-processed 316L stainless steel (316L SS) suffers from insufficient surface conductivity and relatively poor corrosion resistance, resulting in high energy loss and limited operational stability in fuel cell modules. This study utilized active screen plasma nitriding (ASPN) technology to modify LPBF-processed 316L SS. The surface structure evolution of LPBF-processed 316L SS and Wrought-316L SS BPPs under varying nitriding temperatures was systematically investigated. The influence of ASPN temperature on interfacial contact resistance (ICR), corrosion resistance of the nitrided layer, as well as single-cell performance was investigated. Results indicated that at a nitriding temperature of 400 °C, LPBF-processed 316L SS BPPs achieved optimal overall performance (microhardness 287.4 HV 0.3 , ICR 112 mΩ·cm 2 , corrosion potential -151 mV, corrosion current density 0.005 mA/cm 2 ). The LPBF-processed 316L SS BPP, treated under the optimized ASPN temperature, exhibited the highest peak power density (0.194 W/cm 2 ) in single-cell tests compared to the gold-sprayed LPBF-processed 316L SS BPP (0.163 W/cm 2 ) and untreated LPBF-processed 316L SS BPP (0.121 W/cm 2 ). During a 10-hour continuous operation, the ASPN-treated BPP maintained the internal resistance of only 22 mΩ, lower than gold-sprayed BPP (39 mΩ) and untreated BPP (202 mΩ), confirming its robust operational stability. These findings highlighted the potential of ASPN-treated LPBF-processed 316L SS as high-performance metal BPPs, paving the way for broader application of LPBF technology in fuel cell manufacturing.