Porosity Formation due to Splat Curling-up in Thermal Spray Coating Technology: ANumerical Approach

The curling up of the splat rim in a thermal spray coating process is simulated using a 2D numerical approach (Ansys). As a simplifying assumption, the splat is considered to be a flat disk of uniform thickness and temperature. The droplet is considered to be flattened completely and the solidification process starts afterwards. The solidification process is modeled using enthalpy method. A typical case corresponding to athermal spray scenario was considered. By simulating different scenarios, it is found that the curl-up angle is sensitive to some parameters such as the thickness and radius of the splat, the splat and substrate temperature difference, and thermo physical properties of both splat and substrate materials such as their coefficient of thermal expansion (CTE), thermal conductivity, and the splat heat of fusion. Close inspection of the results reveals that the curl-up angle increases with increasing substrate temperature, the CTE, substrate thermal conductivity and adhesion of the splat to the substrate. Other factors, such as the splat heat of fusion and the splat thickness have a reverse effect on the curl-up angle.

Keywords:

curling up , thermal spray coating , thermal stress , porosity , numerical approach