The Effects of Thermal Shrinkage on Coating Formation in Thermal Spray Processes:A Numerical Approach

In this paper, we performed a numerical study on the effects of thermal shrinkage on the deposition of molten tin droplets on a steel substrate in thermal spray coating process using Volume-of-Fluid (VOF) method. Thermal shrinkage is a phenomenon caused by variation of density during solidification and cooling down of molten metal. The Navier-Stokes equations along with the energy equation including phase change are solved using a 2-D axisymmetric mesh. We used the VOF method, applied to the fixed Eulerian mesh, to track the free surface of the droplet. For solidification, we used an enthalpy-porosity formulation. The simulations performed in this study are accomplished using both a commercial code (FLUENT) and an inhouse developed program. The results of these scenarios are presented: the normal impacts of 2.7mm spherical tin droplets at 1m/s and 2m/s, initially at 240°C, onto a 27°C steel substrate. It is seen that when the droplet impacts to the substrate with 1m/s velocity, it spreads and solidifies and during the recoil of the droplet, a single cavity forms within the splat which is the source of porosity and is caused by shrinkage.

کلیدواژه ها:

thermal shrinkage ، thermal spray coating ، VOF method ، solidification ، droplets