Phase composition and residual stresses in thermal barrier coatings

The phase composition and the residual stresses in multilayer thermal barrier coatings, which consist of an external ZrO₂–8Y₂O₃ ceramic layer, an intermediate gradient (metal ceramic) layer, and a transient metallic NiCrAlY sublayer, are studied. It is shown that an increase in the specific volume of the metallic sublayer as a result of the formation of thermal growing oxide Al₂O₃ generates high compressive stresses in this sublayer. The ceramic layer undergoes tensile stresses in this case. A method is proposed to estimate the stresses in gradient coatings from X-ray diffraction results.