Silicon nitride (Si3N4)

 

Silicon nitride (Si3N4) currently plays a clearly dominant role among nitride ceramics and has a combination of outstanding material properties that has not been achieved by other ceramics, such as

• high toughness

• high strength, even at high temperatures

• excellent thermal shock resistance

• excellent wear resistance

• low thermal expansion

• medium thermal conductivity

• good chemical resistance

 

This combination of properties results in a ceramic that is suitable for the most extreme operating conditions.

Silicon nitride ceramics are therefore predestined for machine components with very high dynamic loads and reliability requirements.

In order to produce dense silicon nitride ceramics, a submicron Si3N4 powder mixed with sintering additives (Al2O3, Y2O3, MgO etc.) is assumed, which is sintered at temperatures between 1,750 and 1,950 ° C after the shaping process. Due to the decomposition of Si3N4 to (Si and N2) from approx. 1,700 ° C at normal pressure of the sintering atmosphere, the N2 pressure is increased during sintering in order to counteract the decomposition.

Silicon nitride is used as a special material in bearing technology for hybrid bearings (rolling elements made of Si3N4) and all-ceramic bearings (rolling elements and races made of Si3N4).