奥氏体不锈钢双极板的低温超饱和气体渗碳表面改性

By the means of low temperature colossal supersaturation gaseous carburization (LTCSGC) technique, a carburizing layer of 30 μm was formed on the surface of 316L austenitic stainless steel bipolar plate. The carbon concentration, compressive residual stress, nano-hardness and the phase structure along cross-sectional depth direction of the specimens were investigated, respectively. Besides, the contact resistance of carburized 316L stainless steel bipolar plates was measured and the corrosion resistance of the samples in simulated proton exchange membrane fuel cell (PEMFC) environment was analyzed. Results demonstrate that the LTCSGC layer was a functionally gradient material which was composed of expanded austenite. Moreover, its carbon concentration, residual stress and hardness decline continuously along cross-sectional depth direction from surface to substrate. Compared with 316L stainless steel bipolar plates, the contact resistance of carburized samples after LTCSGC treatment was reduced by 34%. The self-corrosion potential in PEMFC anode environment was improved to -79 mV, which was higher than the PEMFC work potential (-0.1 V). Therefore, it was protected by cathode. In PEMFC simulated cathode environment, the self-corrosion potential was increased by 260 mV and the corrosion resistance was remarkably improved. Meanwhile, the potentiostatic polarization etching current density was reduced by 75%.