Properties of hardmetals related to their constitution

Alloys with a cobalt binder content in the range from 3 to 15 wt.% were studied. The carbides grain size also range between 0.7 and 5 μm. Mechanical properties, such as transverse rupture strength and hardness, were tested. The residual porosity and the micro structure were accurately observed by optical microscopy and the carbide grain size was estimated using an optical image analyser. The results of this study show that it is possible to increase the hardness characteristics by decreasing both the carbide grain size and the Co content, whilst the transverse rupture strength increases with higher Co content. So the properties of hardmetals result in a compromise between the competing requirements of hardness and of toughness.