Manufacturing complex-shaped microchannels on proton exchange membrane fuel cell(PEMFC)bipolar plates poses challenges,and surface roughness significantly affects their performance and lifespan.Laser powder bed fusion(LPBF),with its high degree of formability and capability to produce complex structures,offers significant advantages in forming these intricate microchannels.Moreover,abrasive flow machining enables efficient polishing of complex channels.LPBF was employed to fabricate 316L stainless steel PEMFC bipolar plates with complex-shaped microchannel structures.Optimized laser parameters(laser power of 150 W,scanning speed of 800 mm/s,and scanning spacing of 50 μm)resulted in a sample density of 99.5%.A custom abrasive flow polishing device and fixtures were developed to optimize the polishing process for LPBF-fabricated microchannels.Through experimen-tal techniques including optical microscopy,laser confocal microscopy,and scanning electron microscopy,the effects of different polishing pressures on the dimensional accuracy,surface roughness,and microstructure of LPBF-fabricated PEMFC bipolar plates with complex-shaped microchannels were investigated.Optimal abrasive flow pol-ishing parameters(polishing pressure of 9 MPa,polishing time of 90 min,and abrasive particle size of 0.037 5 mm)were determined.Increasing the polishing pressure effectively enhanced the quality of the microchannel inner walls and significantly improved the unevenness along the length of the microchannels.At polishing pressures of 9-11 MPa,surface roughness of the fabricated components reduced to 2.43-3.57 μm,with an improvement of up to 77.9%-85.7%.The top of the channel structure exhibited the lowest hardness and the most significant variation,correlating with the density and microstructure at the hanging position.Specifically,at a polishing pressure of 9 MPa,the total design deviation at the midpoint and exit of the microchannels was minimized,measuring 61 μm and 82 μm,respectively.The mechanism of abrasive flow polishing for LPBF-formed PEMFC bipolar plates with complex-shaped microchannels was elucidated,aiming to provide insights into surface finishing for LPBF-formed intricate structures.
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