Formation and Effect of Hierarchical Structures on Corrosion Performance of Stainless Steel Bipolar Plate Fabricated by Powder Bed Fusion

Bipolar plate (BP) is a conductive element in proton-exchange membrane fuel cell (PEMFC), which is developing towards the ultra-micro and ultra-lightweight directions, as well as complex shape channels. Additive manufacturing (AM) exhibits unique superiority in printing micro-BP with complex flow channels. However, the special non-equilibrium microstructures generated by quick heat and cooling process of AM, characterized by hierarchical and multi-scaled microstructures, display a complex effect on the corrosion resistance in PEMFCs, and require to be systematically investigated. Thin-walled stainless steel (SS) BPs with a star-shape flow field were fabricated by powder bed fusion (PBF). Considering the structural heterogeneity induced by the cooling rate of the different thin-walled shapes, full-scaled microstructure analysis and its effect on corrosion performance are investigated in simulated PEMFCs operating environments. The results show that the PBFed 304L SS delivers a multi-scaled microstructure, featured with micron-scaled melting arc, submicron-scaled grains, nano-scaled cluster cells, nanotwins/ stacking faults, and nanoinclusions, as well as high-density dislocations. The effects of all these microstructures on the pitting and passivation behaviors are explored in the anode and cathode conditions, and compared with the wrought counterpart. Additionally, another two practical performances of conductivity and hydrophobicity required by PEMFCs are also evaluated. The PBFed specimens exhibit a significant improvement of intergranular corrosion in the anode and pitting in the cathode, represented by higher E corr and lower I corr during the electrochemical tests. Compared with the wrought SS specimens, the ultra-fined grains and nano-scaled cluster cells in PBFed SS advance the spread of passivation film, while the melting arc and column grains slightly degrade the corrosion resistance performance. The dependent relationship of multiscaled microstructure with the cooling rate is discussed.

Keywords: powder bed fusion, Stainless steel, Microstructure, Corrosion resistance, Passive film

Suggested Citation: Suggested Citation

Chen, Aiying and Jiang, Jungan and Li, Xiang and Hou, Juan and Ding, Zhiyi and Gan, Bin and Zhang, Kai, Formation and Effect of Hierarchical Structures on Corrosion Performance of Stainless Steel Bipolar Plate Fabricated by Powder Bed Fusion. Available at SSRN: https://ssrn.com/abstract=4239103 or http://dx.doi.org/10.2139/ssrn.4239103