Common bearing surface treatment technologies

Rolling bearings vary in type ( puller bearing, one-way clutch bearing, turret bearing, conrod bearing), size ( 17 x 37 x 12 bearing), and application conditions. Different materials are used for various components, such as bearing steel GCr15SiMn or carburized steel G20Cr2Ni4A. Manufacturing typically involves processes like outer ring forging, lathe machining, heat treatment, grinding, and automated assembly. From a market perspective, the cost of different types of bearings varies significantly. Ball bearing prices fluctuate greatly depending on materials and precision. For example, SKF bearings are generally more expensive than ordinary products due to brand premium and technological advantages. Cheap ball bearings are often suitable for simple equipment with low performance requirements. Full ceramic bearings are relatively expensive due to their high temperature and corrosion resistance. Sealed waterproof bearings are widely used in humid or dusty environments because of their dustproof and waterproof features. To ensure bearings meet various technical requirements such as greater durability, longer lifespan, higher reliability, and suitability for harsher operating environments, surface treatment technologies for bearing working surfaces have become widely used, driven by the continuous emergence and development of new processing technologies. Common bearing surface treatment techniques include physical surface deformation treatment, chemical treatment, heat treatment, and surface thin-film coating treatment, among others.

Mechanical processing methods induce plastic deformation on the bearing surface, forming a high-strength, high-hardness, and high-density hardened layer. This physical deformation strengthening treatment is also known as deformation strengthening or work hardening. Commonly used processes include shot peening, sandblasting, finishing, cold rolling, polishing, and ultra-precision finishing. Whether it's a connecting rod bearing subjected to impact loads or a 17 x 37 x 12 bearing with high precision requirements, the performance is significantly improved after this treatment. Mechanical extrusion deformation of the bearing surface increases dislocation density and refines the subgrain structure, enhancing surface hardness and strength, and significantly improving the surface fatigue strength of the parts. Simultaneously, sandblasting eliminates surface stress and reduces heat treatment cracking; polishing and ultra-precision finishing reduce surface roughness, improve surface microstructure, and enhance the fit and oil film quality between components in the bearing's rolling area. For example, after polishing, the friction coefficient of a puller bearing is significantly reduced, extending its service life; and ultra-precision finishing optimizes the reverse locking accuracy of a one-way clutch bearing. Physical deformation surface strengthening methods are simple, effective, and facilitate process quality control.

The method of strengthening a bearing surface by altering its chemical composition through the solid-state infiltration of a certain element is called chemical heat treatment or diffusion heat treatment. This includes processes such as chromizing, carburizing, carbonitriding, sulfide and sulfur-nitrogen-carbon co-diffusion, and graphitization, where the infiltrating element either dissolves into the base metal to form a solid solution or forms compounds with other metallic elements. Commonly used carburizing steel heat treatment processes result in a bearing surface hardness similar to high-carbon chromium bearing steel, with a softer core. The carburized layer depth is typically 0.8–3.5 mm, with a surface hardness of HRC58–64 and a core hardness of HRC32–48. Carburized steel possesses high hardness and is suitable for turret bearings and other applications in the machine tool industry where they withstand harsh, high-impact loads. It also meets the additional corrosion resistance requirements of sealed waterproof bearings in humid environments. Blackening modification of the bearing surface involves heating the parts in a strong alkaline solution to oxidize the surface, creating a dense, firmly bonded iron oxide film on the bearing surface. The purpose of blackening treatment is to give bearings good rust and corrosion resistance, high wear resistance, self-lubricating properties, and a glossy and aesthetically pleasing surface. The blackening heating process also helps reduce internal stress. Cage phosphating and bearing component pickling are also considered blackening processes. Inexpensive ball bearings often undergo blackening treatment to reduce production costs while simultaneously improving basic rust resistance. Although full ceramic bearings are inherently highly corrosion-resistant, this process is still used to further optimize surface properties under certain special operating conditions.

Surface heat treatment utilizes solid-state phase transformation, employing rapid heating to harden the surface layer of bearings; this is known as surface hardening. Methods include flame hardening and high (medium) frequency induction hardening. Its characteristics include: rapid localized surface hardening with minimal workpiece deformation, short heating time, high production efficiency, and slight surface oxidation and decarburization. It is suitable for the surface heat treatment of large bearings, such as turret bearings. Surface hardening improves their impact load resistance and provides higher wear resistance and contact fatigue strength. For conrod bearings, which frequently withstand cyclic loads, surface hardening is also a key process for extending their service life.

A coating is applied to a metal surface and then physically or chemically bonded to the substrate to form a reinforced film with different material properties. This includes electroplating, chemical plating (chromium, nickel, silver, etc.), composite plating, and brush plating. The key feature is that all of these methods form a thin film with specific properties on the bearing surface, improving its wear resistance, fatigue resistance, corrosion resistance, and self-lubricating properties. This treatment method is also used in bearing repair solutions. For example, SKF bearings, which are relatively expensive, can have their service life extended through brush plating repair for some slightly worn bearings; sealed waterproof bearings can have their waterproof sealing further enhanced through nickel plating; and for full ceramic bearings with minor scratches, composite plating processes can achieve precise repair, avoiding the high costs of complete replacement.

The above are some common bearing surface treatment technologies that are frequently used by many bearing manufacturers for the outer ring surface treatment of bearings. For more practical bearing anti-rust processes and durable stainless steel bearing models, please contact BLH Bearing Factory.

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