Sintering behaviour of alumina-tungsten carbide composites

Alumina reinforced with tungsten carbide has been investigated as an altern ative material for metalworking, combining resistance to high service tempe ratures and improved toughness. Pressureless sintered and hot-pressed Al2O3 -WC composites were manufactured and characterised. The use of Y2O3 as a si ntering additive has also been evaluated. Additions of up to 30 wt.% WC res ulted in limited grain boundary pinning and corresponding high densificatio n. Although the addition of Y2O3 improved sintering, the presence of a resi dual grain boundary phase (YAG) was harmful to the fracture toughness of th e composites, as it affected the effectiveness of the crack deflection mech anism that takes place at the interfaces between Al2O3 and WC grains. Hot-p ressing resulted in hardness similar to 17.5 GPa and fracture toughness sim ilar to 7 MPa m(-1/2), which is an improvement compared to alumina reinforc ed by other refractory carbides. (C) 2000 Elsevier Science S.A. All rights reserved.