Microstructure and property of multilayer TiN/TiCN nanocrystalline coating used for metal bipolar plate

Metal bipolar plate (BPP) is one of the key components in proton exchange membrane fuel cell (PEMFC). However, the high interfacial contact resistance and poor corrosion resistance of BPP remain the great challenges for its commercialization. In this study, multilayer TiN/TiCN coatings were designed, and multi-arc ion plated on AISI 316L stainless steel used for BPP in PEMFC. Effects of gas pressure on the microstructure and properties of multilayer TiN/TiCN coatings were evaluated. The results show that microstructures of the multilayer TiN/TiCN coatings are dense with nanocrystalline grains. Gas pressure has no big influence on the thickness of coatings, which is about 2 μm in the present investigation conditions. The multilayer TiN/TiCN nanocrystalline coatings are shown in good corrosion resistances in the simulated solution of PEMFC, especially for the one obtained under 1.0 Pa, which achieves the best corrosion resistance. The interfacial contact resistances of the multilayer TiN/TiCN nanocrystalline coatings are decreased evidently, which can be decreased to as low as 1.82 mΩ·cm2 at 1.4 MPa for the one obtained under 1.0 Pa. The present findings offer a substantial support for the commercial viability of BPP coated with the multilayer TiN/TiCN nanocrystalline coating.