Active screen plasma nitriding of 316 stainless steel for the application of bipolar plates in proton exchange membrane fuel cells

Proton exchange membrane fuel cell (PEMFC) has attracted considerable interest because of its superb performance, and many researches are focused on the development of highperformance, long-life bipolar plates. Stainless steel bipolar plates offer many advantages over the conventional graphite bipolar plates, such as low material and fabrication cost, excellent mechanical behaviour and ease of mass production. However, the insufficient corrosion resistance and relatively high interfacial contact resistance (ICR) become the major obstacles to the widespread use of stainless steel bipolar plates. In this work, active screen plasma nitriding (ASPN), a novel plasma nitriding technique, was used to modify thesurfaceof316austeniticstainlesssteel.Avarietyofanalyticaltechniques,includingXraydiffraction(XRD),scanningelectronmicroscopy(SEM),glowdischargeopticalemission spectrometer (GDOES), were employed to characterize the nitrided samples. The results reveal thatanitrogen supersaturated S-phase layerhasbeensuccessfully produced onthe surface of all nitrided 316 stainless steel samples. The interfacial contact resistance (ICR) valuecanbedecreaseddramaticallyafterASPNtreatmentandthecorrosionresistancecan also been improved. In addition, better corrosion resistance can be achieved by active screen plasma nitriding with a stainless steel screen than with a carbon steel screen. This technique could beusedtoimprovetheperformanceand lifespan ofbipolar platesforfuel cells.