Strength, deformation, and equation of state of tungsten carbide to 66 GPa

Hard ceramics like tungsten carbide exhibit remarkable physical properties such as wear-resistance, ultra-incompressibility, and high yield stress, yet the quasi-static yield strength and deformation of WC have not been studied at high pressure. Its equation of state is also debated, with a reported bulk modulus from 329 to 452 GPa and pressure derivative from 1.25 to 5.45. We compressed bulk and nano-crystalline WC to 66 GPa in the diamond anvil cell with synchrotron X-ray diffraction at the Advanced Photon Source Sector 16. In quasi-hydrostatic Ne medium, nano WC is slightly more compressible than bulk WC, with respective bulk moduli of K₀ = 377 ± 7 and 397 ± 7 GPa and pressure derivatives K₀’ = 3.8 ± 0.3 and 3.3 ± 0.3. Strength and plasticity were determined by Rietveld refinement of lattice strain and texture. Slip mechanisms were determined by Elasto-viscoplastic self-consistent simulations of strain and texture. Preferred orientation occurs at ~30 GPa, with WC sustaining differential stress of ~12-15 GPa. Above yielding, WC has similar strength to other hard materials. Deformation is accommodated by prismatic slip on {10-10}<-12-10> and {10-10}<0001>, with pyramidal slip on {10-10}<-2113> activated at ~40-50 GPa. These mechanisms differ from basal slip in W and hcp metals.