Thermal Stress and Residual Stress Control of Thermally Sprayed 80Ni20Cr Coating

In order to find an effective method to control the residual coating stress after thermal spraying, an analysis and experiment were carried out on a cylindrical member of 80Ni20Cr/SUS304. Temperature measurements during the processes of thermal spraying, heating and cold thermal shock were carried out. Using these measured results, thermal stress analyses were perfomed by the finite element method(FEM) and a proposed simplified method for estimating the coating stress. Thermal stress of the coating obtained by FEM was compared to that obtained by the simplified method and good agreement was obtained between them. Moreover, the residual coating stress after the thermal spraying was measured by the X-ray diffraction method and compared with the estimated results, and good agreement was obtained between them. Based on the simplified method, a control method of the residual coating stress after the thermal spraying was proposed. According to this control method, compressive residual stress can be expected by controlling the preheating temperature of the substrate irrespective of the magnitude of the thermal expansion coefficient of the coating and that of the substrate.