What is the relationship between material hardness and wear resistance

Wear resistance refers to the influence of the ability to resist friction. The factors of this ability not only depend on the composition, structure and properties of the steel, such as hardness, carbide characteristics, quantity, shape and distribution, but also closely related to the conditions of use and the stretching process, such as: There is a large amount of ash layer sand on the surface of the wire.

　　 Hardness is an important performance index to measure the hardness of metal materials. It can be understood as the ability of the material to resist elastic deformation, plastic deformation or destruction, and it can also be expressed as the ability of the material to resist residual deformation and anti-destruction.

　　 Without considering other factors, the higher the hardness, the better the wear resistance. The good wear resistance of cast iron is because gray cast iron contains flake graphite. We know that graphite has lubricating properties. Therefore, although the hardness of cast iron is low, the wear resistance is good because of the reduction of graphite and the surface finish. The higher the surface finish, the lower the friction. Relatively speaking, the hardness and wear resistance of the same material are different depending on the surface treatment. proportional.

　　The higher the hardness of the material, the better the wear resistance, so the hardness value is often used as one of the important indicators to measure the wear resistance of the material.

However, the material with the best wear resistance is not necessarily high in hardness. The most commonly used wear-resistant materials such as cast iron have low hardness. The camshaft of the engine is usually cast iron. More typically, the wear-resistant layer in the sliding bearing is Babbitt alloy. The hardness is not high, and in order to enhance the wear resistance of the worm and worm gear reducer, the worm wheel is generally made of a low-hardness bronze alloy. Wear resistance requires embedding and friction compliance, that is, the friction surface with the unevenness of the two friction surfaces can be formed the fastest after the material is ground. If the surface hardness is purely pursued, too hard materials are not easy to run-in, but will reduce the wear resistance of the friction surface.

　　According to the mechanism of wear:

　　 If it is plunge wear, increasing the surface hardness can better improve the wear resistance; if it is impact wear, the improvement effect will be less.

　　 High manganese steel should be familiar to everyone, and it has good impact and wear resistance. The austenite with good toughness undergoes strong work hardening during impact, improves the surface hardness, and achieves a good combination of hardness and toughness, and has a good wear resistance effect.

　　 If the material contains materials with a lamellar structure such as graphite, hexagonal boron nitride, iron sulfide, etc., these materials act as solid lubricants in friction and can improve wear resistance. Common cast iron, seal coating in aircraft engines, etc.

　　 When plastic and metal are rubbed against each other, the plastic has good adaptability, and it can also form a thin layer of transfer film on the metal surface to improve the wear resistance. The use of PEEK valves instead of metal valves in reciprocating compressors is a good example.

　　 Babbitt alloy is a very classic alloy under oil lubrication conditions. Its structure is that the hard points are distributed on the soft phase. During friction, the hard points play a supporting role, and the soft phase is slightly worn away. The gap formed just contains the lubricating oil and improves the lubricating condition.

　　 High hardness does not mean good wear resistance. High hardness and good wear resistance, it is still useful as an empirical preliminary judgment. If under the same conditions (same friction coefficient, composition, structure, environmental conditions, etc.), there is a non-linear proportional relationship between hardness and wear resistance.

　　Abrasion should actually be the category of contact surface stress, that is, the ratio of material consumption to the interaction of two moving metals under a certain pressure. under these circumstances,

　　High hardness is better than low wear resistance;

　　 Good lubrication is better than bad lubrication;

　　The surface specific pressure is smaller than the larger, and the wear resistance is better (including contact area and pressure);

　　 Low surface roughness is better than high surface roughness;

　　The internal structure of carbide is better than other crystal structures (martensite, ferrite, etc.).

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