Material distortion in laser-based additive manufacturing of fuel cell component: Three-dimensional numerical analysis

Laser powder bed fusion (LPBF), an important additive manufacturing (AM) technique, has received a great deal of research attention and industrial application. The capability to fabricate complicated shapes and structures enables this technique to be applied for the manufacturing of rapid prototypes and complex parts. In operation, the constant melting and cooling of metal powders in a layer-by-layer fashion leads to large gradients and a rapid evolution of temperature, which may cause considerable residual stress and deformation. Polymer electrolyte membrane (PEM) fuel cells are a major type of fuel cells that operate under low temperature with high efficiency. PEM fuel cell components must be free of major distortion to avoid leakage of the reactant gases, intrusion of contaminants, and a large interfacial resistance. In this study, a three-dimensional (3D) numerical study is conducted to investigate the residual stress and deformation in a fuel cell inlet/outlet fitting directly built on the bipolar plate by LPBF. Both Inconel 718 (IN718) and stainless steel 316 L (SS316L) are used as the building materials. The distortion prifle predictions are compered with literature data. Additionally, the validated tool is employed to investigate several major parameters in LPBF fabrication to assess their impacts on distortion, including laser power, laser speed, and layer thickness. In our case, the laser power and speed have a significant impact on the distortion of the inlet/outlet fitting. SS316L shows a much less distortion (about 40 µm) than that of IN71 (about 90 µm) for the maximum distortion and a nearly 30% smaller average distortion at all measuring locations. The middle height of the fitting is subject to the largest distortion. A strain parameter ε^* is discussed to facilitate the analysis of the simulation results.