Pressureless sintering of β-SiC with Al2O3 additions

Abstract

β-SiC was pressureless sintered to 98% theoretical density using Al2O3 as a liquid-phase forming additive. The reaction between SiC and Al2O3 which results in gaseous products, was inhibited by using a pressurized CO gas or, alternatively, a sealed crucible. The densification behaviour and microstructural development of this material are described. The microstructure consists of fine elongated α-SiC grains (maximum length ≈ 10 μm and width 2–3 μm) in a matrix of fine equi-axed grains (2–3 μm) and plate-like grains (2–5μm). The densification behaviour, composition and phases in the sintered product were studied as a function of the sintering parameters and the initial composition. Typically, 50% of the β-phase was transformed to the α-phase.