Abstract:An elasticplastic finite element model for gradient coatings with sandwich structure was formulated to study stresses developed at Al2O3 gradient ceramic coatings during thermal stress.The influence of structure parameters such as the layout of interlayer/metal,the thickness of gradient coatings on the thermal barrier resistance was analyzed.Analyses were conducted for a axisymmetric cylindrical specimen geometries relevant to coating.The graded microstructure was treated as a series of perfectly bonded layers,each having slightly different properties.Constitutive relations for the interlayers were estimated using a modified ruleofmixtures approximation The results show gradient structure can reduce the shear stress mutation in the joint surface between the coating and the substrate compared with the nongraded interface,the maximum shear stresses of the coatings is significantly reduced.Reasonable graded structure can effectively improve the shear stress distribution of the coatings and change the characteristics of shear stress distribution.It shows that in some cases,optimization of the microstructure is required to achieve reductions in certain critical stress components believed to be important for controlling interface failure,and an adopting gradient structure of 10 power exponent is proposed,and 8 interlayers with 20 mm thick can effectively reduce shear stresses mutations.