Silicon Nitride Si₃N₄

Key properties of this material include thermal shock resistance as well as fracture toughness.  These coupled with high temperature strength and wear resistance even under oxidizing conditions make silicon nitride an excellent candidate for IC engine and turbine applications. 

Silicon nitride is difficult to produce as a bulk material in the preferred hot press sintering method as the components dissociate over 1850C.  Lower temperature methods have been developed using sintering aids or by spark sintering.  Results in every case though do drive the cost of this material above most technical ceramics. 

The sintered material can be further fabricated to precise features and tolerance by diamond grinding.  Some of the very properties of silicon nitride that make it attractive for application make it likewise more difficult to grind than other technical ceramics.  Grinding is most productive when the material submits to micro impacts and is less resistant to wear in general.  Grinding silicon nitride therefore forces lower material removal rates than with alumina for example which results in higher fabrication cost.

Silicon nitride does provide excellent performance for specific applications like turbochargers, rocket engines, ball bearings, and cutting tools for cast iron.  Precision machined components are possible for many new applications as well based on the unique properties of this material.  Such cases warrant careful analysis of design to minimize features requiring extensive machining. Cost can limit wider application but the unique property benefits to performance of key components can optimize project performance and make or break success.