Anatomy: Reasons for Failure of FAG Bearings

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FAG bearings are widely used in industrial applications due to their high precision and durability. However, despite their robust design, these bearings can still fail under certain conditions. Understanding the root causes of failure is crucial for maintaining performance and extending service life. One of the main factors contributing to FAG bearing failure is the grinding process itself. During grinding, the interaction between the grinding wheel and the workpiece generates significant heat and mechanical forces. These factors can lead to various surface and subsurface changes that affect the bearing's integrity. First, the **grinding heat** can reach extremely high temperatures—up to 1000–1500°C—within a very short time frame (0.1 to 0.001 ms). This intense heat can cause several issues: - **Oxidation layer**: A thin layer of iron oxide forms on the surface, typically 20–30 nm thick. The thickness of this layer correlates with the depth of the affected area, making it a useful indicator of grinding quality. - **Amorphous layer**: At such high temperatures, the surface may melt slightly, forming a very thin amorphous layer (around 10 nm). While this layer has high hardness, it is easily removed during fine grinding. - **High-temperature tempering**: If the temperature exceeds the material’s tempering point, it can lead to a reduction in hardness and structural changes. - **Secondary quenching**: When the surface reaches above the austenitizing temperature (Ac1), it can transform into martensite upon cooling. However, this often results in a high-temperature tempering layer beneath it. - **Grinding cracks**: The stress from rapid heating and cooling can cause microcracks, especially at the interface between different layers, which can propagate and eventually lead to bearing failure. In addition to thermal effects, **mechanical forces** from the grinding wheel also play a critical role. The cutting, friction, and clamping forces exerted by the wheel can cause plastic deformation and work hardening on the surface. - **Cold plastic deformation**: As the abrasive grains interact with the workpiece, they can cause a plastic deformation layer, especially when the wheel becomes dull or the feed rate increases. - **Thermoplastic deformation**: High temperatures reduce the elastic limit of the material, leading to further deformation under pressure. - **Work hardening**: This is a common result of repeated grinding, where the surface becomes harder due to plastic deformation. It can be detected using microhardness testing or metallography. Moreover, residual layers from previous manufacturing steps—such as decarburization from casting or heat treatment—can remain if not fully removed. These layers can weaken the surface, increasing the risk of early failure. To prevent FAG bearing failures, it's essential to monitor and control the grinding parameters, ensure proper cooling, and maintain high-quality finishing processes. Regular inspection and maintenance can also help identify early signs of wear or damage. For more information on bearing technology, check out our related articles: - Detailed analysis: "Sliding bearing" skills and layout features of thrust ball bearings used in the automotive industry - Timken bearing introduction: bearing application (2) - SKF Swedish bearing front and rear code (1) This article is sourced from China Bearing Network. For more details, visit [http://www.chinabearing.net](http://www.chinabearing.net). Previous: DL linear drive simplifies installation Next: Features of imported bearings, bearing seals, and dust covers

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