Effect of Y2O3 addition on the densification and mechanical properties of alumina-niobium carbide composites

Alumina-based composites reinforced with refractory carbides are potential cutting tool materials. They exceed the capabilities of cemented carbides w ith respect to hot hardness and thermal stability, resulting in faster cutt ing speeds. Liquid-phase sintering of Al2O3-NbC composites was investigated as an alternative to pressure-assisted processes. Al2O3 reinforced by NbC (5-40 wt.%) was sintered with 3 wt.% Y2O3 In order to assess the effect of the formation of a liquid phase on the properties of the composites, sinter ing was carried out either below or above the Al2O3-Y2O3 eutectic temperatu re, at 1650 and 1800 degreesC, respectively. Density, hardness, fracture to ughness and wear resistance of the composite materials were evaluated. Liqu id phase sintering did not affect the fracture toughness, but improved both the density and the hardness of the material, regardless of its NbC conten ts. Higher concentrations of NbC increased the wear resistance of the compo site. (C) 2001 Published by Elsevier Science Ltd and Techna S.r.l. All righ ts reserved.