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Technical Ceramics


Si3N4 Silicon Nitride Ceramic Bearing Balls

The unique combination of material properties of Silicon Nitride makes it ideal for applications with high dynamic stresses, thermal rigor, and demanding reliability requirements, meanwhile, it provides advantages in severe-service applications such as turbines and high-end ball bearings.
  • Density :

    3.3 g/cm3
  • Max. Service Temp. :

    1200 degree C
  • Thermal Conductivity :

    27 W/m.K
  • Dielectric Strength :

    20 KV/mm
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Product Detail

Material Introduction

Silicon nitride ceramic balls are precision ceramics sintered at high temperature in a non-oxidizing atmosphere. It has high strength, high wear resistance, high temperature resistance, corrosion resistance, acid and alkali resistance, and can be used for a long time in seawaterand has good performance of electrical and magnetic insulation. At 800, the strength and hardness are almost unchanged. Its density is 3.20g/cm3, which is almost 1/3 of the weight of steel bearing. The centrifugal force is small during rotation. High-speed operation can be achieved. It also has self-lubricating properties, and it can be used in environments where no lubricating medium is highly polluted. Become the first choice for ceramic bearings and hybrid ceramic ball bearings.

The superiority of silicon nitride bearing material:

- Small density, small centrifugal force, more conducive to high-speed operation

The density of silicon nitride ceramic material is about 3.2, while the density of steel bearing is about 7.8. The density of silicon nitride ceramics is only about 40% of the density of steel bearing. Therefore, when the rolling element uses silicon nitride ceramics, the bearing can effectively suppress the increase in the rolling element load caused by the centrifugal force when the bearing rotates at high speed. Therefore, the use of low-density silicon nitride balls is more conducive to the development of high-speed bearings.

- Heat resistance, can adapt to higher temperature working conditions

Generally, when the operating temperature of steel bearings exceeds 120°C, the hardness will decrease and the rolling life will also decrease. For example: the service temperature limit of M50 high-temperature steel bearing is about 400℃. When this temperature is reached, the hardness of the steel decreases greatly. However, silicon nitride completely maintains its original hardness in this temperature range. Only at about 800℃, its hardness and strength began to decline. Therefore, for bearings used in high-temperature environments, silicon nitride materials are very suitable. For example: aviation jet engines, gas turbines, nuclear reactor systems, X-ray tube tungsten disks, and rockets and spacecraft.

- small linear expansion coefficient, can be used in the field of environmental temperature changes

The linear expansion coefficient of silicon nitride is about 1/4 of that of steel bearing, so the dimensional change of silicon nitride bearing material with temperature changes is small.

Anti-locking: Therefore, the bearing made of silicon nitride ceramic material can effectively prevent the bearing material from "locking" due to temperature changes and dimensional changes. So as to ensure the stable operation of the equipment and reduce the loss due to equipment failure.

- Excellent self-lubricating performance

Silicon nitride ceramic material itself has the functions of anti-friction, anti-wear and lubrication. Under bad lubrication conditions, such as oil-lean lubrication and oil-free dry friction, it shows superior anti-friction and self-lubricating performance. It has a good emergency state, which can effectively avoid losses caused by sudden equipment failures.

The self-lubricating mechanism of silicon nitride is still controversial. At present, some scholars believe that the main reason for this characteristic is that silicon nitride decomposes in a small amount during the friction process and forms a very thin film on the surface, thereby reducing the frictional resistance. And as the friction continues, the friction surface becomes more and more smooth, and the resistance becomes smaller and smaller, which has the effect of lubricating and reducing wear.

- Stable chemical properties-corrosion resistance

Silicon nitride has good chemical resistance to most acids, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and alkali. Only hydrofluoric acid or a mixture of hydrochloric acid and nitric acid can corrode silicon hydride.

Therefore, the bearing material made of silicon nitride can be exposed to corrosive acid, alkali, salt and other solutions for a long time. Compared with steel bearings, its average life will be 4-25 times longer than stainless steel bearings. It can be applied to machinery used in chemical machinery equipment, food, marine, sewage treatment and other departments to reduce the trouble caused by corrosion.

- Non-magnetic, insulating

In a strong magnetic environment, when steel bearings are used, the fine powder worn down from the bearing itself is adsorbed on the rolling elements and rolling surfaces, which will become the main cause of early spalling damage and increased noise.

The use of bearing steel to prepare the bearings of the railway vehicle traction motor will cause electric corrosion, which will reduce the life of the traction motor bearing. The use of insulated full ceramic silicon nitride bearing materials can effectively improve the impact of electrical corrosion on the bearing.

Compared with steel bearings, the main advantages of silicon nitride bearings are:

1. It is 59% lighter than steel bearings, which greatly reduces the centrifugal force, rolling and wear of the bearing on the raceway during high-speed and accelerated operation;

2. The modulus of elasticity is 44% larger than that of steel, which means that the amount of deformation is much smaller than that of steel balls when subjected to force;

3. The hardness is higher than steel, HRC reaches 78;

4. Small friction coefficient;

5. The thermal expansion coefficient is 1/4 of that of steel, which can withstand drastic changes in temperature;

6. It is easy to obtain almost perfect surface finish, Ra can reach 46nm;

7. High temperature resistance: Silicon nitride ceramic balls still have high strength and hardness at 1050°C;

8. Never rust, and can work without oil lubrication;

9. More resistant to chemical corrosion than steel;

10. No metal pollution;

11. Non-magnetic;

12. Electrical insulation.

13. There is no adhesion and wear;

The combination of these excellent properties makes silicon nitride the first choice for high-performance bearing rolling element materials.

Technical Properties of Si3N4 Silicon Nitride Ceramic

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