Material Factor and Control of Bearing Life (2)
The second material factor to affect bearing service life is surface hardness. When bearing rollers roll on the inner and outer raceways, they cut into the material, which causes plastic deformation of the raceway to reduce the rolling resistance and generates heat. If the raceways are too soft, the bearing will generate more heat, the raceway surface layers will be deform more quickly, and the bearing service life will be reduced significantly. Because hardness affects the plasticity and toughness of the material, it is an important factor affecting service life.
In order to improve the surface hardness of bearing raceways, surface hardening treatments such as nitriding, hardening and tempering, carbonitration and carbonizing have been developed. Hardening is a process that forms a hard wear-resistant surface layer on the bearing by heating and cooling the bearing material. It is mainly used for medium and small bearings used in internal combustion engines and other harsh environment. Carbonitration is a thermal diffusion process combined with a high temperature carburization technique often used to produce surface layers with a combined pretour and wear resistance. Carbonizing is a low temperature thermal diffusion process which is typically used to provide internal and external bearing raceways for tribological applications.
Aside from these surface hardening treatments, material selection and optimization of heat treatment process can also help improve the surface hardness of bearing raceways. The material selected should not only have high hardness and wear resistance overall, but also appropriate hardness batch by batch. This is because if the selected materials are too hard and can not produce uniform hardness on the surface of the bearing, it will lead to uneven wear, which in turn results in poor service life of the bearing. Meanwhile, the heat treatment process should be appropriately optimized according to different production conditions and enviroments to ensure that the bearing roller and raceway hardness meets the requirements.
In addition, the surface finish quality of bearing raceways also affects its service life to some extent. The surface of bearing raceway should have a certain roughness and waviness, so as to minimize sliding between the contact surface and the rolling element, reduce the rolling resistance and reduce the generated heat, so as to improve the bearing service life. However, too much or too little roughness and waviness will have a greater impact on bearing service life. Therefore, it is important to carefully control the surface finish when manufacturing bearing raceways.
In short, the surface hardness and surface finish of bearing raceway material have a great influence on bearing service life. Therefore, it is important to select the appropriate material and optimize the thermal treatments of the bearing to ensure the hardness of the bearing raceway is appropriate. The surface finish of the bearing raceway should also be carefully controlled to ensure that it meets the requirements.
