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

The thermal conductivities of $\alpha {\mathrm{-Al}}_2{\mathrm{O}}_3$ and $\kappa {\mathrm{-Al}}_2{\mathrm{O}}_3$ wear-resistant coatings are measured using the $\text{3ω}$ method in the temperature range $\text{80<T<600}$ K. The coatings are 13 $\mu \mathrm{m}$ thick and deposited by chemical vapor deposition on substrates of Co-cemented WC. The $\alpha {\mathrm{-Al}}_2{\mathrm{O}}_3$ coating has a thermal conductivity comparable to sapphire at $\text{T>300}$ K. The relatively small thermal conductivity of $\kappa {\mathrm{-Al}}_2{\mathrm{O}}_3$ , a factor of $\text{∼3}$ smaller than $\alpha {\mathrm{-Al}}_2{\mathrm{O}}_3$ , suggests that this metastable phase of alumina can be applied as an effective thermal barrier for cutting tools.