Residual Stresses in Suspension Plasma Sprayed Electrolytes in Metal-Supported solid Oxide Fuel Cell

This study is aimed at identifying the change of residual stresses in suspension plasma sprayed (SPS) 8 mol% YSZ electrolytes on top of porous stainless steel substrate with varying processing parameters and temperatures. The residual stresses in the electrolyte layer are tensile with a value of approximately 90 MPa at room temperature. Porosity, microcracks and segmentation cracks are observed to form in the coating during post-deposition cooling. The decrease of residual stresses with increasing temperature is related to the changes in the Young’s modulus, thermal expansion mismatch, micro-defects and possible creeping of porous stainless steel substrate. The coating fabricated using a torch power of 133 kW and stand-off distance of 90 mm exhibits the highest residual stress due to the formation of a denser microstructure and less cracking. Furthermore, the fracture toughness and interface fracture toughness of the SPS YSZ coating at the optimized condition was determined and discussed.