Compressibility and strength of nanocrystalline tungsten boride under compression to 60 GPa

The compression behavior and stress state of nanocrystalline tungsten boride (WB) were investigated using radial x-ray diffraction (RXRD) in a diamond-anvil cell under non-hydrostatic compression up to 60.4 GPa. The compression properties and stress state are analyzed using lattice strain theory. Experiments were conducted at beamline X17C of the National Synchrotron Light Source. The radial x-ray diffraction data yield a bulk modulus that is qualitatively consistent with density functional theory calculations and demonstrate that WB is a highly incompressible material. A maximum differential stress, t, of about 14 GPa can be supported by nanocrystalline WB at the highest pressure. This corresponds to about 5% of the shear modulus, G, which is smaller than the values of t/G (∼8%-10%) observed for BC ₂N, B ₆O, TiB ₂, and γ-Si ₃N ₄ at high pressures. Thus, while WB is highly incompressible, its strength is relatively low at high pressures compared to other hard ceramics.