How to Evaluate the Wear Resistance of Materials?

"Abrasion resistance" is also called wear resistance, the wear resistance of materials, expressed by the amount of wear or the wear resistance index. Wear is a very common phenomenon, and there are many reasons for this phenomenon, including physical, chemical and mechanical factors. The main ones are: abrasive wear, adhesive wear (bonding), fatigue wear (pitting), and corrosive wear. In terms of adhesive wear, when solid surfaces come into contact, their high and low peaks will prevent the two solid surfaces from 100% contact. The protruding parts come into contact with each other, and due to the large pressure, they produce plastic deformation, which causes cold welding, that is, adhesion. The adhesion part causes one side of the weaker material to be sheared due to friction and sliding, causing the material to be adhered from the weaker side to the stronger side.

Main factors affecting material wear resistance

Hardness

The wear resistance of metal materials can be measured by the [hardness] of the material, mainly because the hardness of the material reflects the material's ability to resist the material from pressing into the surface. The deeper the material presses into the material surface, the smaller the wear volume generated by cutting, that is, the smaller the wear and the higher the wear resistance. Therefore, increasing the hardness of the material's metal structure can generally improve the material's wear resistance. However, due to differences in the composition and structure of the material, the material structure may not be suitable for a certain specific wear condition, and the hardness cannot be a sufficient basis for comparing the wear resistance of the material.

Mutual solubility of crystals in crystal structure

Metal materials with hexagonal closepacked structure (HCP) have a friction coefficient of 0.2-0.4 and a low wear rate even when the friction surface is very clean. Cobalt stone is a typical material of this type, so it can be used as an important component of hardness-resistant alloys. A pair of metal friction pairs with poor metallurgical solubility can obtain a lower friction coefficient and wear rate. For example, if the material that forms a pair of friction pairs with steel has a low solubility in iron, or if this material is an intermetallic compound, the wear resistance of the friction pair surface is better.

Temperature

Temperature mainly changes the wear resistance of metal materials by affecting the transformation of hardness crystal structure and increasing oxidation rate. The hardness of metals usually decreases with increasing temperature, so the wear rate increases with increasing temperature. Some friction parts (such as high-temperature bearings and cutting tools) require the use of materials with high thermal hardness. The material factory should contain alloy elements such as cobalt, chromium and molybdenum. The miscibility of friction pairs can be regarded as a function of temperature. If the temperature rises, the materials are easy to dissolve, which affects the wear rate of the materials. In addition, the increase in temperature promotes the increase in oxidation rate and has a significant impact on the type of oxides generated. Therefore, it also plays an important role in the wear performance of metals.

Plasticity and toughness

High plasticity and toughness indicate that the material can absorb a lot of energy, cracks are not easy to form, the material has a large ability to deform repeatedly, and is not easy to form fatigue wear, that is, good wear resistance. Tests show that different materials with the same hardness have different wear resistance. Similarly, different materials with the same toughness have different wear resistance. For example, the hardness of the quenched state sample and the quenched + tempered sample may be the same. However, due to different toughness, the wear resistance is different. In fact, the wear resistance is different due to the different quality microstructures, but if the microstructure of the wear-resistant material is the same, the hardness can be used to measure the wear resistance.

Strength

During the wear process, the metal matrix has high strength, which can provide good support for the wear-resistant hard phase, give full play to the wear resistance of the wear-resistant hard phase, and make the wear-resistant material show excellent wear resistance. At the same hardness, high-strength wear-resistant materials have better wear resistance.

Metallurgical defects such as inclusions

Metallurgical defects such as non-plastic inclusions in steel have a serious impact on fatigue wear. For example, angular particles such as nitrides, oxides, and silicates in steel cannot be coordinated with the matrix during stress, forming gaps and stress concentration sources. Cracks appear and expand under the action of alternating stress, eventually leading to early fatigue wear.

Surface roughness

Under certain contact stress conditions, the smaller the surface roughness value, the higher the fatigue wear resistance. When the surface roughness value is small to a certain value, the impact on fatigue wear resistance will be reduced.