Thermal conductivity of κ-Al₂O₃ and α-Al₂O₃ wear-resistant coatings

The thermal conductivities of α-Al₂O₃ and κ-Al₂O₃ wear-resistant coatings are measured using the 3ω method in the temperature range 80<T<600 K. The coatings are 13 μm thick and deposited by chemical vapor deposition on substrates of Co-cemented WC. The α-Al₂O₃ coating has a thermal conductivity comparable to sapphire at T>300 K. The relatively small thermal conductivity of κ-Al₂O₃, a factor of ∼3 smaller than α-Al₂O₃, suggests that this metastable phase of alumina can be applied as an effective thermal barrier for cutting tools.