Properties of sintered WC-TiC-Co hard alloys containing tantalum carbide

1.The alloying of WC-TiC-Co alloys with tantalum carbide increases their bending strength (at moderated temperatures), hardness (at high temperatures), thermal cycling resistance, and oxidation resistance.2.It is shown that, in the brittle fracture region of WC-TiC-TaC-Co alloys, the relationship between bending strength and volumetric cobalt content is quite accurately described by the equation s²=AEC, where s is bending strength, E is the modulus of elasticity, C is cobalt content, and A is a constant. Observations under the microscope have confirmed that the rupture crack is propagated through the cementing phase (and along phase boundaries), and avoids the carbide grains.3.It is shown that, when tantalum carbide is added to WC-TiC-Co alloys, the composition of the cementing phase undergoes a marked change, which alone may be sufficient for increasing the strength of both this phase and the alloys. The latter may also be promoted by the improved wetting of the carbide crystals by the molten cementing phase during sintering.