High-temperature deformation of plasma-sprayed ZrO2 thermal barrier coatings

The high-temperature deformation of atmospheric plasma-sprayed ZrO2 thermal barrier coatings (TBCs) was investigated. Compression creep tests were performed at temperatures between 900 and 1300°C at stresses between 1.8 and 80 MPa. During 100 h creep time a secondary creep region was not achieved. The creep behavior can be described by a power law. Besides the creep deformation, a shrinkage of the material was observed in a differential dilatometer, leading to a tremendous change of the elastic properties. Finite element calculations showed that the coatings are in a tensile stress state during high-temperature application in gas turbine engines so that two competing high-temperature deformation mechanisms exist in such an application. The thermomechanical state of stress of a coated gas turbine component was simulated by laser irradiation in relaxation tests to investigate which mechanism would control the deformation. An interferometric measurement of the deformation showed a stretching of the coating, due to either tensile creep or crack growth.