功能梯度涂层热残余应力

涂层中的残余应力严重影响着涂层零件的机械完整性与操作可靠性。对于功能梯度涂层,由于各界面位移协调条件的限制,很难得到涂层内部残余应力的闭合解。基于传统的悬臂梁理论,获得了功能梯度涂层热残余应力的闭合解;这一分析模型的优点是残余应力的闭合解与涂层层数无关。讨论了采用传统的近似解所带来的误差, 针对含不同层数的ZrO2/NiCoCrAlY功能梯度涂层内部的残余应力进行了计算。另外,对应力诱导的涂层失效模型也进行了分析。

THERMAL RESIDUAL STRESSES IN FUNCTIONALLY GRADED COATINGS

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.