Determining the thermal conductivity of ceramic coatings by relative method

Abstract Thermal conductivity is a crucial parameter for evaluating the quality and thermal effects of ceramic coatings, especially for thermal barrier coatings. However, measurement by conventional method involves two problems: (a) it is difficult to peel off a ceramic coating from a substrate; (b) even if the coating can be peeled off, it is still hardly used as standard specimen in test. Therefore, the relative method was proposed to evaluate the thermal conductivity of ceramic coating. An analytical relationship among the thermal conductivities of the coating, the substrate, and the coating/substrate composite was established. Experiments on TA4 coated with YSZ coatings were carried out to demonstrate the feasibility of this novel method and to investigate the impact of temperature on the thermal conductivity of YSZ coatings. The experimental results demonstrated the validity and convenience of the relative method. With the increasing testing temperature, the thermal conductivity value of YSZ coatings displayed nonlinearity feature, that is, decreased from 1.4 to 1.3 (W m ⁻¹ K ⁻¹ ) in the temperature range of 32‐300°C and then increased up to 1.58 W m ⁻¹ K ⁻¹ at 1000°C.