Silicon Nitride is a monolithic ceramic, boasting exceptional hardness and superb fracture resistance.
It is used as a material for cutting tools thanks to its toughness, thermal stability and resistance to wear, which make it particularly suitable for speed machining of cast iron.
For steel machining, it is usually coated by titanium nitride in order to increase chemical resistance.
Silicon nitride is useful in such applications subjected to a constantly important thermal shock and high loads stress ( for instance welding points) as well as in high temperature machining, demanding good electric insulation.