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Surface strengthening method of stainless steel bearing

wallpapers Industry 2020-02-23

What are the methods to strengthen the surface of stainless steel bearing

The working surface and the core of stainless steel bearing parts are quite different in the state, structure, and performance requirements. However, the overall heat treatment often makes the two aspects unable to be considered, and the potential of the material is not fully exploited. The surface strengthening technology of stainless steel bearing materials can not only solve the differences in structure and requirements between the surface and the center but also make the surface obtain some special working performance, so as to meet the requirements of working surface performance of bearings working under specific conditions. This is of great significance in the development of modern science and technology.

The traditional surface strengthening method belongs to the category of heat treatment. The surface strengthening methods developed in modern times, such as laser, electron beam, an ion beam, not only apply some high and new technologies to the surface strengthening of materials but also go beyond the scope of traditional heat treatment in technology, forming a new technical field. Therefore, the current surface strengthening technology can form a variety of classification methods from different perspectives. According to the physical and chemical process of surface strengthening technology, it can be roughly divided into five categories:

1. Surface deformation strengthening

2. Surface heat treatment strengthening

3. Chemical heat treatment strengthening

4. Surface metallurgical strengthening

5. Surface film strengthening.

Methods of surface strengthening

1. Deformation strengthening of stainless steel bearing surface

The metal surface layer is plastically deformed by the mechanical method to form a hardening layer with high hardness and strength. This surface strengthening method is called surface deformation strengthening, also known as work hardening. Including shot peening, it is sandblasting, cold extrusion, rolling, cold rolling and impact, explosion impact strengthening, etc.

Characteristic:

1.1 with the increase of dislocation density and refinement of sub crystal structure, the hardness and strength of the strengthened layer are increased, and the surface roughness value is reduced, which can significantly improve the surface fatigue strength of the parts and reduce the sensitivity of fatigue notch.

1.2 the strengthening process is simple and effective, there is no obvious boundary between the hardening layer and the matrix, the structure is coherent, and it is not easy to fall off in use.

1.3 most of its methods have been applied in the stainless steel bearing industry: the surface impact strengthening of the rolling body is the application of such methods, and precision rolling has become a new method of ring processing and strengthening.

Heat treatment strengthening of stainless steel bearing surface

The surface heat treatment, commonly known as surface quenching, is to quench the surface layer of parts by means of solid-state transformation and rapid heating. It includes flame heating quenching, high (medium) frequency induction heating quenching, laser heating or electron beam heating quenching.

Characteristic:

2.1 the surface is locally heated and quenched, and the workpiece deformation is small;

2.2 high heating speed and high production efficiency;

2.3 short heating time and slight surface oxidation and decarburization.

2.4 especially, it can improve the wear resistance and fatigue strength of large and extra-large bearing parts under certain impact load.

Strengthening of stainless steel by chemical heat treatment

3.1 to change the chemical composition of the metal surface layer by the solid diffusion infiltration of an element, the method to realize the surface strengthening is called chemical heat treatment strengthening, also known as diffusion heat treatment.

3.2 it includes boronizing, metalizing, carburizing and carbonitriding, nitriding and nitrocarburizing, sulfurizing and sulfur nitrocarburizing, chromizing, aluminizing, and chromizing aluminosilicate, graphitizing layer, etc., with various types and characteristics. Infiltrate elements or dissolve into the base metal to form a solid solution, or combine with other metal elements to form a compound.

3.3 in a word, penetrating elements can change the chemical composition of the surface layer and obtain different phase structures. The treatment process of carburized stainless steel bearing parts and the surface nitriding treatment of needle bearing sleeve belongs to this kind of strengthening method.

Metallurgical strengthening of the stainless steel surface

Surface metallurgical strengthening is a technology that uses the remelting and solidification of the surface layer metal to obtain the desired composition or structure. It includes surface self soluble alloy or composite powder coating, surface melting crystallization or amorphous treatment, surface alloying, and other methods.

Characteristic

4.1 high energy density rapid heating is used to melt the metal surface layer or the alloying material coated on the metal surface, and then it is cooled by itself to solidify to obtain the strengthening layer with the special structure or specific performance.

4.3 the special structure may be fine crystal structure, supersaturated phase, metastable phase, or even amorphous structure, which depends on the process parameters and methods of surface metallurgy.

Thin-film strengthening of the stainless steel surface

Using physical or chemical methods to coat the metal surface with different strengthening films of different properties on the base material is called surface film strengthening. It includes electroplating, electroless plating (chromium plating, nickel plating, copper plating, silver plating, etc.) and composite plating, brush plating, or conversion treatment, as well as high and new technologies that have developed rapidly in recent years.

Characteristic

5.1 it can form special performance film on the working surface so as to strengthen the wear resistance, fatigue resistance, corrosion resistance, self-lubrication, and other properties of the surface.

5.2. for example, the strengthening of bearing working surface by ion implantation technology can significantly improve the wear resistance, corrosion resistance, and contact fatigue resistance of bearing working surface, so that the service life of bearing can be multiplied.


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