Effect of tungsten carbide additions on the microstructure and properties of hot-pressed alumina

Studies published in the literature have shown that alumina reinforced with refractory carbides is a good alternative to cemented carbides, for cutting tools and wear-resistant applications. In this work, alumina reinforced with tungsten carbide was homogenised and mixed in a planetary ball mill and subsequently hot-pressed at 1450 °C under 20 MPa in flowing argon. Hot-pressing resulted in a material with a hardness and fracture toughness of 19 GPa and 7.1 MPa m1/2, respectively. X-ray diffraction analysis showed the presence of alumina and WC. No other new crystalline phase was identified. The sintered material showed a very homogeneous distribution of small dark grains of WC in an alumina matrix, which appears to have very large grains with very clean grain boundaries. The WC grains tend to lie on grain boundaries but can also be seen at triple points. The material also shows large alumina grains containing WC inclusions, which points to the possible occurrence of abnormal grain growth.