Improvement of Oxidation Resistance and Adhesion Strength of Thermal Barrier Coating by Grinding and Grit-Blasting Treatments

Abstract

The formation of thermally grown oxide (TGO), which is composed of alumina and mixed oxides, leads to the delamination of thermal barrier coating (TBC). In this study, to improve the oxidation resistance and adhesion strength of TBCs, grinding and grit-blasting treatments with alumina grits were applied to the surface of the bond-coat (BC) before deposition of the top-coat (TC). These treatments are expected to pre-form an alumina layer as an oxidation barrier and also optimize the TC/BC interfacial roughness. A high-temperature exposure test of TBC specimens grit-blasted with alumina grits of different sizes (B-TBC) revealed the growth of a continuous alumina layer in the B-TBC specimens in contrast to the formation of a complex TGO with alumina and mixed oxides in non-blasted TBC (S-TBC). Moreover, the area and thickness of TGO in the B-TBC specimens were much lower than those in the S-TBC. An indentation test was conducted to evaluate the TC/BC interfacial fracture toughness KIFC which confirmed a significantly higher KIFC of the B-TBC specimens than that of the S-TBC specimen. These results demonstrated that the grinding and grit-blasting treatments are effective in improving the oxidation resistance and adhesion strength of the TBC system.