Bearing materials

It is known to all that bearing materials are various. Different kinds of materials have different functions, advantages and disadvantages. Steel is a main kind of material that is used for producing bearing products. But in some environments, this material can not be performed well.

Compared to steel, ceramic materials have many specific advantages. They offer superior corrosion and heat resistance, higher dimensional stability, and lower density, which facilitate high speed. Ceramics are superior to steel in heat and corrosion resistance, and are lightweight and extremely hard as well. Consequently, ceramic rolling bearings can be used in environments where conventional steel bearings cannot. That is to say, the superiority of these bearings makes it possible that they can be applied in some special environments.

Firstly, they can be used in corrosive environments. Compared to stainless steel bearings, hybrid and all-ceramic bearings lasted three and twenty times longer respectively. It is presumed that water readily adheres to silicon nitride and forms a better lubrication film, leading to extended bearing life.

Secondly, they can be performed in corrosive agents. Generally, silicon nitride has excellent corrosion resistance. However, corrosion resistance varies depending on the type and quantity of sintering additives, and certain corrosive agents decrease in hardness and flexural strength. In such situation, it is can be proved that the carbide-based ceramic bearings are the most effective.

Thirdly, they can be used in high-temperature vacuum. An all-silicon nitride ball bearing with a self-lubricating laminated cage (mainly composed of MoS2) and with MoS2-coated rings and balls proved superior in durability in a high-temperature vacuum environment. Compared with the hybrid bearings, the all-ceramic bearing was superior in both dynamic frictional torque and life.

Fourthly, they can be performed with poor lubrication. As ceramics are extremely hard and have outstanding wear resistance, they outperform other materials in bearing life without lubrication. According to a test, the steel bearing seized within a short period while the hybrid and all-ceramic bearings, though sustaining wear, did not. And the all-ceramic bearing sustained considerably less wear than the hybrid bearing, indicating that its endurance life is much longer.