Measurement of temperature-dependent thermal conductivity for PVD Ti0.55Al0.45N ceramic coating by time domain thermo-reflectance method

Abstract

Accurate measuring temperature-dependent thermal conductivities of (Ti,Al)N ceramic coating is important to quantitatively analyze the thermal effects of (Ti,Al)N ceramic coating on the heat generation and heat transfer during cutting process by PVD (Ti,Al)N coated cemented tools. In this paper, the temperature-dependent thermal conductivities of PVD Ti0.55Al0.45N ceramic coating with coating thickness of 2 µm in the temperature ranges of 25–500 °C are measured by time domain thermo-reflectance method. Firstly, the detailed deposition process and microstructure characterization of PVD Ti0.55Al0.45N ceramic coating are presented. Secondly, the measuring principle and measuring procedure of PVD ceramic coating thermal conductivity with the time domain thermo-reflectance are proposed. Then, the measured thermal properties of substrate are used in the calculation algorithm to obtain the thermal conductivity of Ti0.55Al0.45N ceramic coating at the specific temperature, which can eliminate the variation influences of substrate thermal properties with temperature. Lastly, the obtained thermal conductivities of PVD Ti0.55Al0.45N ceramic coating are verified to be increased with the increase of temperature in the temperature ranges of 25–500 °C. The relationship between the thermal conductivity of PVD Ti0.55Al0.45N coating and temperature can be represented by quadratic polynominal equation. The applied time domain thermo-reflectance method is useful for measuring the temperature-dependent thermal conductivities of similar ceramic coatings in the temperature ranges of 25–500 °C.