Silicon Nitride (Si3N4) has good high temperature strength, creep resistance and oxidation resistance. In addition, its low thermal expansion coefficient gives good thermal shock resistance compared with most ceramic materials. Silicon nitride is produced in two main ways; Reaction bonded silicon nitride (RBSN), and hot pressed silicon nitride (HPSN) and sintered silicon nitride (SSN). RBSN is made by direct reacting compacted silicon powder with nitrogen, and produces a relatively low-density product compared with hot pressed and sintered silicon nitride, however the process has only a small volume change allowing net shape forming. The HPSN and SSN material is made with sintering aids and offers better physical properties suitable for more demanding applications. Typical Silicon Nitride applications include: Bearing balls and rollers Cutting tools Valves, turbocharger rotors for engines Turbine blades Glow plugs Molten metal handling Thermocouple sheaths Welding jigs and fixtures Welding nozzles Advantages 1.High hardness 2.Wear resistance 3.High fire resistance 4.Corrosion preventive 5.Good chemical stability
