Silicon Nitride
Silicon nitride is an engineering ceramic which can be found in several forms with their own unique properties. These include high strength, toughness and hardness, excellent wear resistance, corrosion resistance to many acids and alkalis and outstanding thermal shock resistance. These materials have several applications and new ones are still being discovered, which has resulted in them becoming more widely accepted and used in many industrial applications. Silicon Nitride is used to produce high-quality components, which can be used in extremely demanding applications.
Types of Silicon Nitride
Silicon nitride cannot be considered as a single material, since its material properties depend on the fabrication method. The four main types of silicon nitride are:
- Reaction bonded silicon nitride (RBSN)
- Hot pressed silicon nitride (HPSN)
- Sintered silicon nitrides (SSN)
- Gas Pressure Assist Sintered (GPA Silicon Nitride)
Key Properties
Applications exploit the following properties of silicon nitride:
- Low density
- High temperature strength
- Superior thermal shock resistance
- Excellent wear resistance
- Good fracture toughness
- Mechanical fatigue and creep resistance
- Good oxidation resistance
Applications
The most common applications of silicon nitride are the following:
Automotive Industry:
Various wear and combustion parts in reciprocating engines where stresses at high temperatures are prevalent.
Diesel engines- silicon nitrides are used in glow plugs (for quicker start-up time), precombustion chambers (to reduce emissions or act as a muffler), and turbochargers (to reduce engine lag).
Cam followers, tappet shims, precision shafts and axles.
Bearings:
- Silicon nitride ceramic ball and roller bearings are preferred over steel for high-temperature applications.
- This prolongs the bearing life at higher speeds as it would possess better corrosion resistance.
- Its higher modulus of elasticity compared to steel indicates that it is more rigid, thus creating a smooth motion and less vibration with the contacting surfaces
Metalworking:
- Metal cutting tools for cast iron
- Hard steel, and nickel-based alloys due to its hardness
- Fracture toughness, and thermal shock resistance.
Material Applications:
- Handling molten metal – for which metallic components are often unsuitable.
- Weld jigs/positioners, spray nozzles, cylinder wall coatings, turbine rotor, blades, pipes for rockets, and missiles employ silicon nitride for its strength, electrical properties and shock resistance.
- Applications in the aluminum casting industry, as well, benefit from silicon nitride’s good corrosion resistance, thermal shock resistance, and thermal conductivity. These include heating tubes, pump liners, riser tubes, and thermocouple protection sheaths.
Biomedical Applications:
- Silicon nitride is projected to become a replacement for titanium and other entrenched biomaterials in many fields of medicine.
- The research indicates this is a close to ideal biomaterial for orthopedic implants.
High End Aerospace Engine Applications:
- High efficiency burners
- Ball bearings
- Radomes
- RF Windows
P R O T O T Y P E
