Ceramic Bearing Ball

Ceramic Bearing Ball

Ceramic structural balls are typically used in bearings and have a supporting function. Ceramic bearing balls are a crucial component of deep groove ball bearings, angular contact bearings, self-aligning ball bearings, thrust ball bearings, etc.

Tags Ceramic Bearing Ball

Ceramic balls have widespread application in machinery and catalytic field. Ceramics are generally made up of atomic crystals joined together by covalent bonds. Covalent bonds have more energy than metal bonds, giving ceramics superior hardness, corrosion resistance, and stable chemical characteristics. Furthermore, because there is a cloud of free electrons around metal bonds, which is not the case in atomic crystals, ceramics are better at insulating heat than metals and are not conductive.

Ceramic bearing balls are mainly made of silicon carbide, silicon nitride, zirconia, alumina, etc. The several ceramic bearing balls are as follows.

Al2O3 Alumina Balls

ZrO2 Zirconia Balls

Si3N4 Silicon Nitride Balls

SiC Silicon Carbide Balls

Silicon Nitride Ceramic Ball

Silicon nitride ceramic ball has the following benefits:

It has a density of 3.2g/cm³. They produce low centrifugal force during high-speed operation as a result of their low density and light weight, which lessens ball slippage and the stress on the bearing sleeve.
It has excellent insulating properties, allowing it to effectively decrease the electric corrosion produced by bearing discharge.
It is corrosion-resistant and suitable for use in harsh circumstances.
It has high hardness, good wear resistance, and low thermal expansion coefficient, making it less likely to deform during high-speed rotation, while also not producing iron filings adhesion like steel bearing balls.
It has smooth surface, and is self-lubricating, which can reduce friction.

Zirconia Ceramic Ball

The following are the advantages of zirconia ceramic ball:

Zirconia bearing ball is often made of yttrium-stabilized zirconia. It has a density of 6.0g/cm3 and is ideal for harsh service environments including chemical production, oil and gas downhole, and other high-pressure, high-temperature, and corrosive applications.
It is almost twice as hard as tungsten carbide and nearly three times the hardness of silicon carbide. As a result, it is more impact-resistant and a perfect material for oil tool applications. Because of its high hardness, it is also more wear-resistant, and the use of zirconia bearing balls reduces the risk of damage from operation.
Zirconia has a thermal expansion coefficient comparable to that of steel, thus if the outside diameter of the shaft or bushing bore size changes with temperature, the zirconia sleeve and bushing will vary significantly. Hence, zirconia ensures a more stable operating preload by reducing cracking issues caused by incompatible coefficients of thermal expansion.
Zirconia bearing ball is also self-lubricating, which reduces noise and vibration while the machine is running.
It is resistant to acid and alkali corrosion, improving durability in harsh environments.
Its working temperature can reach 500°C or higher, and cold temperatures have little effect on it.
It is anti-magnetic and electrical insulating.

Silicon Carbide Ceramic Ball

It has the following advantages:

Silicon carbide has the highest operating temperature. It has outstanding high-temperature strength. When the temperature surpasses 1200 ° C, the strength of SiC begins to exceed that of Si3N4;
It has the highest thermal conductivity--approximately 150W/mK, allowing heat to be dissipated fast during bearing operation.
It has the best thermal shock resistance and can be utilized in situations where the temperature changes quickly.
It has low thermal expansion coefficient, capable of maintaining good dimensional precision in high-temperature environments (only more than Si3N4);
The high elastic modulus enhances the bearing's dynamic rigidity and enables usage in occasions that have high rigidity requirements, such as machine tool spindles;
It has the lowest density, which can be used in high-speed operation environments and reduce friction and centrifugal load;
It has the best corrosion resistance. It can resist corrosion from concentrated acids and alkalis, especially from HF.

Alumina Ceramic Ball

Alumina ceramic ball has the following benefits:

Alumina balls with 99.6% alumina content have a density of 3.95g/cm3, and are 50% lighter than steel balls, which reduces centrifugal force, rolling, and wear on the raceway during high-speed and accelerated bearing operation.
It is resistant to high temperatures that it can maintain dimensional stability when the working temperature is as high as 1000°C.
It has excellent resistance to abrasion, heat and oxidation, and is corrosion-resistant to water, salt solution, acids, and other chemical compounds, but not resistant to hydrochloric acid and hydrofluoric acid, and strong alkali solutions.
It provides high hardness, but poorer fracture toughness than zirconia.
Alumina balls are better suited for occasions with low cost requirements.

The size ranges of ceramic bearing balls are shown below:

Use Fields of Bearing Ball

Aerospace: satellites, jet engines, and wing flap ball screw actuators
Automotive: electric vehicle traction motor shaft bearings, fuel injection systems
Medical: dental drills
Renewable Energy: wind turbine engines
Industrial: machine tools spindles

Applications of Ceramic Bearings

High-Speed Bearing

It has benefits such as cold resistance, low elastic force, high pressure resistance, poor thermal conductivity, light weight, low friction coefficient, etc., and can be utilized on high-speed spindles ranging from 12000 to 75000 rp, as well as other high-precision devices;

High-Temperature-Resistant Bearing

The material itself is self-lubricating and can withstand high temperatures up to 1200°C. The operating temperature does not cause expansion owing to temperature differences between 100°C and 800°C. It can be utilized in high-temperature equipment such as kilns, plastic manufacturing, and steel production.

Corrosion-Resistant Bearing

The material itself features corrosion resistance, making it suitable for use in corrosive environments such as strong acid, strong alkali, inorganic environment, organic salt, seawater, and other fields. To be specific, it can be used in electroplating equipment, electronic equipment, chemical machinery, shipbuilding, medical equipment, etc.

Anti-Magnetic Bearing

Because it is non-magnetic, it does not absorb dust, which can prevent the peeling of the bearing surface, consequently lowering the running noise. It is suitable for use in demagnetization devices and precision instruments.

Electrically Insulated Bearing

It can be used in a variety of electrical devices requiring insulation because of their high resistivity, which helps to prevent arc damage to the bearings.

Vacuum Bearing

Due to the special oil-free self-lubricating properties of ceramic materials, it can overcome the issue that ordinary bearings cannot accomplish lubrication in an ultra-high vacuum environment.

Ceramics vs. Ball Bearing Steel

Ceramics have a self-weight that is 30%-40% that of bearing steel, which can help to lessen the rise in dynamic load and sliding induced by centrifugal force.
The high wear resistance of ceramics allows for rotational speeds that are 1.3–1.5 times that of bearing steel, which helps reduce the damage that high-speed rotation causes to the groove's surface.
The elastic modulus of ceramics is 1.5 times greater than that of bearing steel. Little stress elasticity can diminish deformation brought on by high loads.
The hardness of ceramics is twice that of bearing steel to minimize wear.
Ceramics have 5-7 times the compression resistance of bearing steel.
The thermal expansion coefficient of ceramics is 20% less than that of bearing steel.
The coefficient of friction of ceramics is 30% lower than that of bearing steel, lowering the heat produced by friction and reducing the early peeling failure of bearings brought on by high temperature.
The control variable method simulates the wear of ceramic and steel balls under actual working conditions while subjecting the bearing to the same stress levels, and ceramic balls exhibit greater wear resistance.

Molding Methods of Silicon Nitride Ceramic Balls

Gas pressure sintering and hot isostatic pressing are the two molding methods most commonly used to manufacture silicon nitride ceramic balls. Gas pressure sintering is the process of sintering silicon nitride compact at 1800–2100 °C in nitrogen of 5–12 MPa to yield dense ceramics. And the isostatic pressing uses gas as the pressure medium to ensure that the material (powder, green body, or sintered body) withstands uniform pressure in all directions during the heating process and promotes densification with the aid of high temperature and high pressure, which is advantageous in obtaining ceramic material with high density and uniform structure.

The ball grade is as follows(the unit is μm):