High temperature hardness and thermal analysis of CoNiCrAlY alloys used as bond coats for thermal barrier coatings

CoNiCrAlY alloys, commonly used as the bond coat of thermal barrier coatings (TBCs), are often exposed to high temperatures of about 1000 °C, the evolution of mechanical and thermal properties is critical to the reliability and durability of TBCs. In this paper, the hardness and thermal properties (weight change and heat flow) of CoNiCrAlY alloys at temperatures within 1000 °C were evaluated by indentation and TGA-DSC thermal analysis. It was found that hardness and thermal properties change gradually within 600 °C but change sharply above 600 °C, exhibiting an approximately synchronized evolution. An illustrative explanation was given for the correlation in terms of the Boltzmann energy distribution theory of microscopic particles. Based on these findings, an idea of inter-calibration between the two evolutions was proposed.