Assessment of the amount of residual stresses in a thermal barrier coating system due to deposition process using analytical, experimental and numerical methods

In this paper, residual thermal stresses caused by quenching of layers as well as the thermal expansion mismatch between the coating layers due to a sharp drop in temperature during the deposition process in the thermal barrier coating system is evaluated using an analytical model, experimental tests and a finite element model. Due to the inherent complexity of these coatings, the problem is solved analytically after some simplification. The residual stresses of the coated samples were measures using XRD method. In order to calculate the stress distribution in the whole system, a finite element model is proposed. In this model, the interface profile of the coating layers was extracted based on SEM images so it was considered to be resemble the real case. Also the boundary conditions were applied to this sub model in a way that it is in a good accordance with the experimental tests loading. The analytical results showed that the quenching residual stresses of the layers have a minor amount compared to the thermal mismatch stresses between the layers in the tests. The average value of the measured residual stresses is -150 MPa, which has a good agreement with the results obtained from the analytical and finite element methods.