Studying the structure and adhesion strength of thermal barrier coating

The structure and adhesive strength of thermal barrier coatings produced by successive deposition of layers is studied. The coating is applied in three layers: i) a diffusion aluminosilicide coating that provides protection against high temperature oxidation and corrosion, with a thickness of 50 µm; ii) a metal sublayer providing a smooth transition from a metal coating to a ceramic one, with a thickness of 100 to 120 µm; iii) a ceramic layer decreasing the temperature of the blades during operation, with a thickness of 70 to 100 µm. The total coating thickness ranges from 0.17 to 0.27 mm. It is shown that the second and third layers deposited by plasma spraying are quite dense, the porosity being less than 5 vol%. During tensile tests carried out on an Instron testing machine, the failure of glued samples was always detected in the adhesive joint. The adhesive strength of the applied epoxy-based adhesive was 12 MPa; it can be stated that the adhesive strength of the coating is higher than 12 MPa.