Ceramic Shoulder Bushing

Ceramic shoulder bushing generally has the characteristics of high temperature resistance, corrosion resistance and electrical insulation. Common ceramic materials of ceramic shoulder washer include alumina, zirconia, silicon carbide, silicon nitride and boron nitride, except for boron nitride, which is a soft, low-hardness material, the Mohs hardness of other ceramic materials is as high as 8.0-9.5, this is why they are very good wear-resistant materials. Because of the ultra-high hardness of ceramics, diamond tools can only be selected for ceramic processing. Special fixtures and processes are required to obtain complex shapes and high precision, and the cost will also rise very much. The following is a brief introduction of several materials of ceramic flanged bushings.

◆ Alumina Shoulder Bushing

Alumina(Aluminum Oxide) is the most common technical ceramic material, and it is also a relatively traditional fine ceramic material. The various mechanical properties of aluminum oxide are relatively balanced. Aluminum oxide ceramics have a variety of purity options, the most common are 95% Al2O3 and 99% Al2O3. As the most mature advanced ceramic material, the production process of alumina is the most diverse. Unless there are special requirements, alumina materials can meet the most requirements of the application.

◆ Zirconia Shoulder Bushing

The characteristics of zirconia are wear resistance and insulation. Under normal temperature environment, zirconium oxide has better wear resistance than aluminum oxide, and it can also maintain good electrical insulation in an environment below 500 degrees Celsius. In addition, the elastic modulus and thermal expansion coefficient of zirconium dioxide ceramics are similar to those of steel, so it can be organically combined with steel to form a composite workpiece, and will not be damaged or burst due to inconsistent thermal expansion. Finally, the thermal conductivity of zirconium oxide is very low, only 2.2 W/m.K, so it can also play a role in heat insulation under the conditions of ensuring wear resistance and electrical insulation. This is a characteristic that most other ceramics cannot have.

◆ Silicon Carbide Shoulder Bushing

Silicon carbide ceramic is an artificial mineral with strong covalent bonds and has a hardness that exceeds that of alumina, zirconia and silicon nitride. It has excellent mechanical properties, high-energy bending strength, excellent oxidation resistance, good corrosion resistance, high wear resistance and low friction coefficient, its high temperature strength can be maintained up to 1,400 ℃, it is the best high temperature strength material among ceramic materials, and its oxidation resistance is also the best among all non-oxide ceramics. In particular, silicon carbide ceramics are extremely resistant to sliding wear. However, in terms of electrical insulation performance, silicon carbide is a semiconductor, so it cannot be used as an electrical insulating material.

◆ Silicon Nitride Shoulder Bushing

Silicon nitride (Si3N4) material has a small thermal expansion coefficient and is extremely resistant to high temperatures. Its strength can be maintained to a high temperature of 1,200°C without degradation. It has excellent thermal shock stability and good resistance to cold and thermal shocks. Even it is heated to 1,000°C and cooled rapidly, it will not break, and it has amazing chemical corrosion resistance. It can withstand almost all inorganic acids and caustic soda solutions below 30%. It is a high-performance electrical insulating material.

◆ Boron Nitride Shoulder Bushing

The main application of h-BN hexagonal boron nitride ceramic top hat washer is as a component of a vacuum high-temperature furnace. H-BN material is light in texture. Although its strength and wear resistance are poor, it is very suitable as an electrical insulation and temperature-resistant component in a vacuum high-temperature furnace. Hex BN ceramic top hat washer can withstand up to 2,000 degrees Celsius, and BN has very outstanding thermal shock resistance, so there will be no cracks caused by changes in temperature rise and fall.

A Simple Comparison of Ceramics, Metals and Polymers

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