Effect of Anisotropic Conductive Properties on Heat Transfer and Temperature Distribution of Coatings and Substrates

Abstract

Thermal conductivity was the main thermal parameter that greatly influenced temperature distribution of materials especially in coatings. Some materials such as plasma-sprayed coatings that had a lamellar microstructure displayed the anisotropy of thermal conductivity. Thermal conductivities of isotropy and anisotropy metallic ceramic coatings were calculated and analyzed using Markworth method and parallel plate model, respectively. The influence of anisotropy on heat transfer and temperature distribution of coatings using finite element analysis and Gaussian heat source modal applied locally was investigated. Results showed that in anisotropic coatings the ratio of transverse and vertical thermal conductivity had a maximum value when metal volume fraction was 50%. The temperatures on the edge of heat sources (Th) had a maximum value, and the highest temperatures of substrate (Ts) had a minimum value with the same fraction. The value decreased by 79°C compared to that in the isotropy coatings. The highest temperatures of coatings (Tc) decreased expectedly with metal volume fraction rised. The maximum width of heat affected zone (HAZ) of coating and substrate was 4.52 mm at the metal content of 40%. The minimum HAZ depth was 0.27mm which was very small at the content of 50%, compared with 1.25 mm in isotropic coatings. It revealed that anisotropic conductive properties caused more heat transfer to outer regions and provided better protection for substrate.