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The Role of Nitrogen to Hydrogen Ratio in Evolution of γN Phase and Surface Properties of Plasma-Nitrided 316L Stainless Steel Bipolar Plate
Chunpeng Liua, Fusheng Xua, Zhongyuan Suoa, Chuanwei Lib,*, Jianfeng Gub
aCollege of Mechanical and Electrical Engineering, Jilin Institute of Chemical Technology, Jilin 132022, China
bShanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Abstract:
This study investigated the impact of the nitrogen-to-hydrogen ratio on the evolution of the surface phase composition and properties of plasma-nitrided 316L stainless steel bipolar plates. The surface microstructure and phase composition of the plasma-nitrided sample were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM) with electron backscattered diffraction (EBSD). After plasma nitriding, a uniform cN phase layer formed on the sample surface under high hydrogen conditions. As hydrogen content increased, the thickness of the cN phase layer also increased because hydrogen increases sputtering, removes the oxide film, and accelerates the diffusion of nitrogen atoms into
the sample surface. After plasma nitriding, the hydrophobicity, conductivity, and corrosion resistance of the sample were considerably improved with the increasing hydrogen content in the nitriding atmosphere.
Whenthe N2–H2ratio was 1:7, the interfacial contact resistance and corrosion current density of the sample were reduced to 8mX/cm2 and 1lA/cm2, respectively. The relationship between the evolution of the cN phase and the surface properties of the 316L stainless steel bipolar plate under different nitrogen-to hydrogen ratio conditions is discussed in detail.
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