Thermophysical Properties of α‐Tungsten Carbide

Upper and lower bounds for the thermal expansion of polycrystalline tungsten carbide (α‐WC) are predicted at ultrahigh temperatures from low‐temperature experimental data. The lower bound is obtained from an α V K T V model, where α V is the volume thermal expansion, K T the isothermal bulk modulus for a randomly oriented polycrystalline sample, and V the molar volume. For many materials, the α V K T V product approaches a constant value that is similar to the specific heat at the highest temperatures. The upper bound uses Grüneisen's rule with a constant Grüneisen parameter gamma at temperatures >1.3θ D (where θ D is the Debye temperature) and experimental data below that temperature. Literature data for the thermophysical properties of α‐WC have been reviewed and used in our α V K T V model to calculate a lower bound for the thermal expansion at temperatures >2θ D and to calculate the temperature dependence of the bulk modulus. The ultrahigh‐pressure thermal expansion has been calculated from the lower bound. Model predictions of the thermophysical properties of WC are given for an extended temperature range.