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Investigation of evolution of γN phase anditseffect onconductivity andcorrosionresistance of plasma-nitrided 316Lstainless steel bipolar plate for proton exchange membranefuel cell
Chunpeng Liu1, Chuanwei Li2,∗, Zhenhua Ye2, Zhongyuan Suo1, Feng Jiang1, Jianfeng Gu2,∗
1CollegeofMechanicalandElectricalEngineering,JilinInstituteofChemicalTechnology,Jilin132022,People’sRepublicofChina
2 Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
Abstract:
In this work, the evolution of)x phase and its effect on conductivity and corrosion resistance ofplasma-nitrided 316 L stainless steel bipolar plate was investigated. The results shows that a certainthickness of uniform /x phase layer was formed after plasma-nitriding treatment. As the increasing inplere ytriting timg he tictnesgf)y,phase tayet and itrosenaloms in )yPhase lgyerwes wasformed in )x phase layer because the nitrogen atoms were diffused into) phase to cause the seriouslattice distortion. When the plasma-nitriding time was reached to24 h, the Fe,N compound wasfound on the sample surface. After plasma-nitriding treatment,the conductivity and corrosionresistance of the sample was obviouslyenhanced compared with the untreated sample. With theincreasing in the thickness of)x phase layer,the interfacial contact resistance (ICR)and corrosioncurrent of the sample was gradually reduced. The ICR ofthe sample was reduced to 7 mS?l under 10 hcondition. However,the formation of Fe,N compound and high roughness contributed to theincrease of ICR ofthe sample under 24 h condition, its value was reached to 15 mS2. When the plasma-nitriding time was larger than 10 h,the corrosion resistance of the sample became poor. The formationof cracks in )x phase layer and the high surface roughness resulted in the degradation of corrosionresistance of the sample. Under 5h condition,the comprehensive properties ofthe sample were thebest. The ICR and corrosion ofthe sample were current conductivity and corrosion resistance of thesample were 15 mSl and 5.1 /A cm-2, which werelow 4times and 15 times compared with theuntreated sample.
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