Abstract: The mechanical integrity and operating reliability of coated devices are strongly influenced by the residual stresses in coatings. However, for a functionally graded coating system, because of the displacement compatibility condition at the interface between layers, it is difficult to obtain a closed-form solution of residual stresses within coating. A general solution used to predict the distribution of residual stresses within functionally graded coatings is developed and it is obtained based on the classical beam bending theory. The advantage of this model is that the solution of residual stresses is independent of the number of layers in coatings. The error resulting from the conventional approximate solution is discussed using the simple case of single-layer coating system. Specific results are calculated for elastic thermal stresses in ZrO2/NiCoCrAlY functionally graded coatings, which consist of different layers. Furthermore, the stress-induced failure modes of coating are also analyzed.

Key words: Closed-form solution, Failure, Functionally graded coating, Thermal residual stress