Thermo-radiative and optical properties of a cutting tool based on polycrystalline cubic boron nitride (PCBN)

The normal spectral emissivity of a cutting tool based on polycrystalline cubic boron nitride (PCBN) between 400 degrees C and 1000 degrees C has been measured. Its shape shows significant differences with respect to that of pure cubic boron nitride (c-BN). Therefore, while the reflectance spectrum of pure c-BN can be fitted to a Lorentz model for linear dielectrics, the reflectance spectrum of the cutting tool (calculated from the emissivity using Kirchhoff's laws) requires a combination of a four-parameter Kurosawa model with a double-damping Drude one. A detailed study of the dependence of the emissivity spectrum with temperature is also performed. The experimental data of this paper is required for accurate temperature measurements with radiation thermometers in machining processes.