Classification of Surface Hardening Technology of Imported Bearing Materials

Chemical heat treatment

• Using solid phase diffusion to some elements to change the chemical composition of metal surface layer, in order to realize surface strengthening, it means strengthening chemical heat treatment, also known as thermal diffusion. 
• Including boronizing, carburizing, carburizing and carbonitriding, nitriding and nitrocarburizing, sulfide and sulfur nitrocarburizing, chromizing, infiltration of aluminum and silicon, graphitization layer, etc. Infiltrate elements or dissolve into base metal to form solid solution, or form compounds with other metal elements.Classification of Surface Hardening Technology of Imported Bearing Materials
•  In the short chemical composition, the elements of the surface layer can be changed, and different phase structures can be obtained. The strengthening process of carburized bearing steel and the surface of Timken imported needle roller bearing sleeve are nitrided.Classification of Surface Hardening Technology of Imported Bearing Materials
• Surface deformation strengthening
• The metal surface layer is deformed mechanically and plastically to form a hardened layer with high hardness and high strength. The surface strengthening method is called enhanced surface deformation, also known as work hardening. Including shot blasting, sand blasting, cold extrusion, rolling, rolling and impact, explosion impact, etc. 
• The characteristics of these methods are: strengthening the increase of dislocation density and the refinement of substructure, increasing its hardness and strength and reducing the surface roughness, which can significantly improve the surface fatigue strength of parts and reduce the fatigue notch sensitivity. Classification of Surface Hardening Technology of Imported Bearing Materials
• This reinforcement method has the advantages of simple process, remarkable effect, hardening layer and matrix structure, no obvious boundary between continuity, not easy to fall off and easy to use. Many methods have been applied to the imported bearing industry: using the method of surface impact strengthening this rolling element, precision rolling has become a new reinforcement method for ferrule processing.Classification of Surface Hardening Technology of Imported Bearing Materials
• Surface heat treatment
• The use of solid-state phase transformation and quenching treatment of parts is called surface heat treatment, and the surface layer is rapidly heated, commonly known as surface hardening. Including flame quenching, high (medium) and high frequency induction heating quenching, laser heating or electron beam heating quenching. 
• These methods are characterized by local surface quenching and small workpiece deformation; Fast heating speed and high production efficiency; The heating time is short, and the surface oxidation and decarburization are very slight. This method is especially used to improve the wear resistance and fatigue strength of large and super large imported bearings under obvious impact load.Classification of Surface Hardening Technology of Imported Bearing Materials

Surface metallurgical strengthening

• The melting and solidification of metal surface layer is surface metallurgical strengthening in order to obtain the composition or structure of the expected surface strengthening technology. 
• It includes surface autolytic alloy or composite powder coating, surface melting, crystallization or amorphous treatment, and surface alloying. Rapid heating with high energy density, melting of metal surface layer or coating alloy material, followed by strengthening cooling and curing to obtain special structure or specific properties. Classification of Surface Hardening Technology of Imported Bearing Materials
• This special structure or crystal structure refinement, or perhaps supersaturation stage, metastable phase, or even amorphous structure, according to different process parameters and surface metallurgy methods. The research on laser heating surface strengthening of rolling work in micro imported bearing industry has good results.Classification of Surface Hardening Technology of Imported Bearing Materials
• Membrane surface strengthening
• Using physical or chemical methods, the properties of substrate materials with different reinforcement layers are coated on the metal surface, which is called reinforced surface film. 
• It includes electroplating, electroless plating (chromium, nickel, copper, silver, etc.) and composite electroplating, brush plating or conversion processes, including high technologies that have developed rapidly in recent years, such as CVD, PVD, p-cvd and other vapor deposition film strengthening methods and ion implantation surface strengthening technology (also known as atomic metallurgy Technology). Classification of Surface Hardening Technology of Imported Bearing Materials
• Their common feature is that the film can form specific properties on the working surface, and improve the wear resistance, fatigue resistance, corrosion resistance and self-lubricating performance of the surface. For example, the surface strengthening technology of ion implantation imported bearing can significantly improve the wear resistance, corrosion resistance and contact fatigue resistance of the imported bearing surface, and double the service life of the imported bearing.Classification of Surface Hardening Technology of Imported Bearing Materials