Thermal stress analysis of HVOF sprayed WC-Co/NiAl multilayer coatings on stainless steel substrate using finite element methods

The scope of this study is to find out the effects of thermal cycling on the coating-substrate system of WC-Co coatings by finite element modeling. With this regard, WC-Co/NiAl coating layers were successfully deposited on 316 L stainless steel substrates by using a HVOF technique and microstructural observations were carried out using SEM. The SEM study revealed that the coating was very dense with very low oxide content and had a very good contact with the substrate, indicating a very good bonding to the substrate. Thermal cycling tests were performed at the temperature range of 373 and 873 °K without external load. In finite element modeling (FEM), thermal residual stresses, developed during and after thermal cycling, were determined by using ANSYS software package. It was found that the stress distributions were obtained in the WC-Co/NiAl architectured coating systems during heating and cooling steps because of the different thermal and mechanical properties of the coating layers and substrates. According to thermal analysis results, the calculated tensile stresses were higher than the compressive stresses and also thermal stress components for x-direction were bigger than for y-direction.