Characterization of thermal barrier coatings via a rockwell indentation test

Thermal barrier coating (TBC) is applied to gas turbine blades to protect the metallic substrate from high- temperature gas flow. TBC consists of the following double layers: top coating (TC) with high thermal insulation and bond coating (BC) with high oxidation resistance. To ensure the long-term reliability of TBC, it is necessary to characterize the thermal insulation and adhesion strength of TBC by using a simple method. In this study, an indentation test involving a Rockwell indenter was applied. The indenter was used on the surface of the TBC specimens prepared under different spray conditions to obtain an indentation curve. Subsequently, the relationship between the parameters based on the indentation curve and the coating properties of TBC, such as porosity, thermal conductivity, Young’s modulus, and interfacial fracture toughness, was investigated. The results indicated that the coating properties of TBC can be characterized by the non-dimensional indentation depth, defined as h_r/h_max, and the slope of the loading curve denoted as k₁ in the parameters.