Abstract
The WC-(10, 20)%Co medium carbon alloys with a carbide grain-size smaller than about 0.6 μm (which is the common size in commercially available micrograined alloys) were sintered by using starting WC powder of 0.20μm and adding VC to check grain growth during sintering. The microstructure and transverse-rupture strength of the alloys were mainly studied as functions of grain-size and cobalt content, or mean free path of binder phase (λ).
The strength and hardness of micro-grained alloys with the grain-size from 0.38 to 0.55 μm, which were obtained by adding 3-5% VC in binder, increased and decreased, respectively, with increasing A. Taking an example of the HIP-ed alloy, the strength became higher and it reached the value from 3.3 to 3.9 GPa, depending on A, when the size of structural defects acting as a fracture source was deminished to the size of about 6 μm. The structural defects in micro-grained alloys were often associated with an agglomerated area consisting of CaS and CaO.
