Silicon nitrides (Si3N4) are a range of advanced engineering ceramics characterised by high strength, toughness and hardness and excellent chemical and thermal stability. The current interest in silicon nitride based engineering materials essentially developed from the research in the 1980s into ceramic parts for gas turbine and piston engines. It was envisaged that an engine, predominately made from silicon nitride based parts, such as sialon, would be light weight and be able to operate at higher temperatures than traditional engines resulting in higher efficiencies. Ultimately however, this goal was not realised as a result of a number of factors including cost, the difficulty in reliably fabricating the parts and the inherent brittle nature of ceramics. However, this work led to the development of a number of other industrial applications for silicon nitride based materials, such as in metal forming, industrial wear and molten metal handling.