Thermomechanical analysis of Alumina coatings by APS using a submodelling procedure

Resumen

Protective coatings are an effective way to improve the surface properties of low cost bulk materials. A representative example for this is the alumina coating of aluminium substrate, which is widely implemented in industrial applications for lightweight components with high tribological loads. However, coating processes face difficulties like the difference in thermophysical properties of the involved materials, or the great thermal gradient developed in the coated surface, requiring an analysis of the residual stress distribution to find suitable parameters for the process. The proposed transient heat transfer model of an APS coating process considers the displacement of the heat source associated to the flame. In such cases, it is necessary to build a mesh fine enough to capture the detailed stress/strain states due to thermal expansion at the local region of interest, a thin layer - a few microns - on the metal substrate surface. Unfortunately, the resulting mesh shows an excessive number of nodes and degrees of freedom, and thus, can exceed the available computing resources. An alternative approach is submodelling, in which a global, coarse grid is considered and a local region of interest is analysed separately with a finer mesh in a submodelling procedure. The boundary conditions of the submodel are adopted from the global mesh. In this work, two submodelling levels have been used to arrive at the scale of a single thermal spray splat. Simulation results of the stress inside an alumina coating on aluminium substrate during the coating process are introduced.