Silicon Nitride exhibit characteristics such as high thermal conductivity and good wear resistance. Due to its outstanding performance there is need of development of new materials in this direction.
Silicon nitride has chemical formula Si3N4. It shows a remarkable combination of electrical, mechanical and thermal properties. It is a very important technical ceramic material. It can be used in a variety of applications such as machining, inserts formation and ceramic curling ring etc.
Processing of Silicon Nitride:
Silicon nitride is difficult to produce in bulk due to the fact that it cannot be heated over 1850 °C. At this temperature, dissociation of silicon and nitrogen occurs. Conventional hot press sintering techniques cannot be applied to the processing of Silicon Nitride.
Silicon nitride powders can be bonded together, at lower temperatures by adding additional binders that aids the sintering process. This allows the degree of liquid phase sintering.
The Spark plasma sintering process is a cleaner alternative to this. In this process, rapid heating of the material is done by passing pulses of electric current through the compacted powder. Dense silicon nitride solid has been obtained by this technique. Similar techniques are applied to the Machining Silicon Carbide Process.
Properties of Silicon Carbide:
It is an extremely hard material with exceptional thermal shock and impact resistance. It exceeds most metals, high temperature capabilities. It also has an extraordinary combination of creep and oxidation resistance. Its properties of low thermal conductivity and high wear resistance make it an excellent material with varied industrial applications. Silicon Nitride is an excellent choice when high-temperature and high-load abilities are needed.
Its machining is very easier and faster. The ceramic material is heated to a very high temperature before machining. The heat source used is generally lasers cutting tools. Several ceramic machining systems have been built that uses lasers to eliminate grinding.
The machining of silicon nitride requires special cutting tools. Polycrystalline diamond (PCD) inserts, were found to be most effective. The laser-assisted machining strengthens the ceramic part. Many companies use 200 CNC turning with stable of four lasers. This combination can be used in various configurations to heat the ceramic to the desired temperatures.
Typical Applications of Silicon Nitride
- Used for Induction heating coil supports
- Applied into Molten metal handling such as crucibles and wear plates.
- Composites reinforcement phase
- It is mainly used in Welding jigs, fixtures and weld location pins
- Several Cutting tools in machining
- Dental heat treatment supports
- TIG / Plasma welding nozzles
- Brazing jigs
- Thermocouple sheaths
- Bearings and rollers
The Machining Silicon Nitride Products use lasers to heat the ceramic to a temperature over 1,000°C. This plasticizes the material. Special diamond-tipped cutting tools are used for laser machining. This material cut the ceramic just behind the laser beam.
The intense heating raises the temperature of the ceramic’s sintering aids. The sintering aids are needed to successfully machine the silicon nitride. Silicon nitride exhibits minimal expansion and contraction under extreme temperature.
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