Thermal diffusivity characterization of bond-coat materials used for thermal barrier coatings

Abstract

Thermal barrier coatings (TBC) are the system build from ceramic insulation top-coat with internal bond-coat as an interlayer between ceramic and Ni-based superalloys substrate materials. The basic role of bond-coat is reduction of thermal strain between ceramic top-coat and metallic substrates. The second role is related to improving the oxidation resistance of metallic substrate. From thermal conductivity point of view, TBC’s system is characterized by three different materials. Usually, bond-coats and Ni-based superalloys were treated as materials with similar thermal properties such as specific heat, thermal diffusivity and thermal conductivity. Actually those materials can exhibit much higher divergences than expected. The aim of this article was the characterization of thermal diffusivity of bond-coats material of NiCrAlY type in the form of powders, massive alloy (obtained during sintering in an actual pressure of 15 MPa, in vacuum of 3 × 10−6 MPa, and at temperature 1050 °C with 2 h of exposure in press), and coating after air plasma spraying. Those studies should get the answer on the question how different morphology and processes impact on thermal diffusivity level of the same material.