Simulation of thermal stress predictions for NiTi coating on a stainless-steel substrate using thermal plasma spraying

Thermal stresses arise during the thermal plasma spraying of composite coatings, influenced by the differing thermophysical properties of the substrate and coating materials. This study focuses on a thick coating with a top NiTi layer and a base stainless steel (AISI 304) substrate, along with an epoxy carrier layer. Initially, the substrate is stress-free at the deposition temperature of 1400 °C. Once the coating is applied, the carrier layer activates at 150 °C, introducing thermal stresses before cooling to room temperature (20 °C). Using COMSOL Multiphysics, we examine stress distribution within the assembly at both 150 °C and room temperature. The model treats the thick plate as a two-dimensional solid, with layers assumed to be isotropic and linear elastic. The higher coefficient of thermal expansion in the substrate (17.3 × 10⁻⁶) compared to the coating (11 × 10⁻⁶) results in tensile stresses in the substrate and compressive stresses in the coating.