CONSOLIDATION AND OXIDATION OF ULTRA FINE WC-Co-HfB2 HARD MATERIALS By SPARK PLASMA SINTERING

In this study, a novel composite was fabricated by adding the Hafnium diboride (HfB2()) to conventional WC-Co cemented carbides to enhance the high-temperature properties while retaining the intrinsic high hardness. Using spark plasma sintering, high density (up to 99.4%) WC-6Co-(1, 2.5, 4, and 5.5 wt. %) HfB2 composites were consolidated at 1300 degrees C (100 degrees C/min) under 60 MPa pressure. The microstructural evolution, oxidation layer, and phase constitution of WC-Co-HfB2 were investigated in the distribution of WC grain and solid solution phases by X-ray diffraction and FE- SEM. The WC-Co-HfB2 composite exhibited improved mechanical properties (approximately 2,180.7 kg/mm(2)) than those of conventional WC-Co cemented carbides. The high strength of the fabricated composites was caused by the fine-grade HfB2 precipitate and the solid solution, which enabled the tailoring of mechanical properties.