Sintering behaviour of alumina-niobium carbide composites

Ceramic cutting tools have been developed as a technological alternative to cemented carbides in order to improve cutting speeds and productivity. Al2 O3 reinforced with refractory carbides improve fracture toughness and hardn ess to values appropriate for cutting applications. Al2O3-NbC composites we re either pressureless sintered or hot-pressed without sintering additives. NbC contents ranged from 5 to 30 wt%. Particle dispersion limited the grai n growth of Al2O3 as a result Of the pinning effect. Pressureless sintering resulted in hardness values of approximately 13 GPa and fracture toughness around 3.6 MPa m(1/2). Hot-pressing improved both hardness and fracture to ughness of the material to 19.7 GPa and 4.5 MPa m(1/2), respectively. (C) 2 000 Elsevier Science Ltd. All rights reserved.