93 / 2021-07-02 13:50:30

Laser powder bed fusion of bipolar plate channels with special cross-section shape for the application of PEMFC

Laser powder bed fusion,PEMFC,microchannels,formability

316L stainless steel bipolar plates hold great potential in the field of fuel cells because of their good formability, high corrosion resistance and low cost. However, with the continuous development of complex flow field structures of high-performance bipolar plates, there are many structures which are difficult to be manufactured by traditional subtractive manufacturing and equal manufacturing methods. Because of its ability to directly fabricate complex structures, laser additive manufacturing process has been applied to manufacture 316L stainless steel bipolar plates with complex structural characteristics. In this paper, bipolar plate channels, with the cross-section shape of 0.7 aspect ratio, were fabricated using laser powder bed fusion, and the effects of laser scanning speeds and channel sizes on the formability and surface morphology of channels were systematically studied. The results showed that with the increase of scanning speed (1500-2250 mm/s) or decrease of channel width (L_1.5-L_0.5), the forming quality of channels and the internal surfaces decreased. Under the optimized laser processing parameters (laser power 300 W and scanning speed 1500 mm/s), when the channel width was greater than L_1.25, the size deviation of the special cross-section channels remained within 8%; however, when channel width was below L_1.25, the overall size deviation rose steeply to 20%. In addition, the formability of different sections inside channels were also deeply studied. It was founded that with the inclined angle θ of the section in channels increased from 0° to 127°, the densification behavior and hardness value of the solid at the boundary of the inner contour decreased, while the surface roughness and the probability of surface defects increased. Besides, with the change of the inclined angle θ of the forming part, the morphology of the cross-section molten pool, the mechanism of defects will also change.