Fracture behaviour of WC-Co hardmetals with WC partiaEy substituted by titanium carbide

摘要

The addition of various amounts of TiCo.9 phase in the range from 5wt.% to 20wt.% substituting WC phase was applied in WC-Co hardmetals with 9.5 wt.% bonding cobalt phase. The hardmetals were consolidated using Hot Iso static Pressing (HIP) method at temperature of 1573K and pressure of 1500 atm. The plain strain fracture toughness has been determined from 3PB test on a pre-cracking single edge notched beam (SENB) specimen. The indentation fracture toughness with Vickers cracks for comparison was also measured, which changed from 12 to 9.0 MPa-m~(1/2). The amount of the TiCo.9 phase affected the mechanical and physical properties: Vickers hardness from 12.5 to 14.0 GPa, Young's modulus from 550 to 460 GPa, density from 13.1 to 9.6 g/cm~3, friction coefficient from 0.24 to 0.45, fracture toughness from 16.8 to 11.0 MPa-m~(1/2). Scanning electron microscopy (SEM), X-ray and electron diffraction phase analysis were used to examine the WC-Co hardmetal with addition of the TiCo.9 phase. For comparison, physical and mechanical properties of the WC-Co hardmetals before modification were tested.