ALUMINA CERAMICS WITH PARTICLE INCLUSIONS

Alumina composites have been prepared with particle inclusions of 0-30 wt% titanium carbonitride and/or 0-5 wt% nickel, or nickel plus molybdenum metal. The metal was added in three different ways; as metal powder, as metal oxide, or as the intermetallic compound T2Ni. Pressureless sintering at 1750-degrees-C gave densities varying from 90% of theoretical density to full density. All materials were post-HIPed to full density at 1600-degrees-C before measurement of mechanical properties. Addition of metal alone increased the fracture toughness from 3.0 to 3.7 MPa m1/2, but decreased the Vickers hardness, HV 10, from 1650 to 1500. The simultaneous addition of hard titanium carbonitride inclusions compensated for the decrease in hardness and gave a further increase in fracture toughness. The alumina composites with 5 wt% metal and 30 wt% Ti(C,N) inclusions had a hardness of 1800 and a fracture toughness of about 5 MPa m1/2.