Performance parameters of sliding bearing materials

The material used for the sliding bearing allows foreign hard particles to be embedded in the lubricant, and is resistant to scratches and has high wear resistance. For metallic materials, the low hardness and low modulus of elasticity have good embedding properties, while non-metallic materials such as carbon graphite, although the modulus of elasticity is low, it have poor embedding properties.

Run-in

During the running-in process of the journal and the bearing bush, as they adapt and match each other, the coaxiality error of the journal and the bearing bush is gradually reduced, and the surface roughness parameter value is reduced, so that the contact is uniform, also. the friction and wear rate  reduced.  

Friction compliance

Friction compliance is that the material relies on the elastoplastic deformation of the surface to compensate for the initial poor fit of the sliding friction surface, and then they gradually adapt to the deflection performance of the shaft. Materials with low modulus of elasticity have better compliance. 

Abrasion resistance

Wear resistance reflects the ability of a material to resist repeated wear. Wear resistance is expressed by the reciprocal of wear rate or wear degree and wear amount under the specified wear conditions.

Fatigue resistance

Fatigue resistance refers to the ability of a material to resist fatigue damage under cyclic loading conditions. Under normal service temperature, the strength, hardness, impact strength and uniformity of the bearing material are important factors in the fatigue resistance. Materials with good running-in and embedding properties usually have poor fatigue resistance.

Corrosion resistance

Corrosion resistance refers to the ability of a material to resist corrosion. Lubricating oil will gradually oxidize, produce acidic substances, when it is used in atmospheric conditions, and most lubricating oils also contain extreme pressure additives that corrode bearing materials. Therefore, bearing materials need to be resistant to corrosion.

Cavitation resistance

Being the solid material moves in the state relative to the liquid, as the bubbles ruptured in the liquid near the solid surface, local impact high pressure or local high temperature will be generated, which cause cavitation wear. The ability of a material to resist cavitation wear is called cavitation resistance. Generally, copper-lead alloys, tin-based bearing alloys and aluminum-zinc-silicon alloys have better cavitation resistance.

Friction compatibility

Friction compatibility refers to the performance of boundary lubrication, it prevents from the adhesion when the shaft direct contacts with bearing bush, the material factors that affect friction compatibility of the friction pair are:

(1) The difficulty of repetitive material metallurgy to form an alloy.

(2) The affinity of materials and lubricants.

(3) The friction factor of the repeated material in the non-lubricated state.

(4) The microstructure of the material.

(5) The thermal conductivity of the material.

(6) The size of the material surface and the characteristics of the oxide film.

Embeddedness

The ability of the material to prevent from scratches or (and) abrasive wear by allowing foreign hard particles to be embedded in the lubricant For metallic materials, those with low hardness and low modulus of elasticity have good embeddability, while non-metallic materials may not. For example, carbon graphite has low elastic modulus but poor embeddability. Sliding bearings are usually made of softer and harder materials to form friction pairs, and generally use softer materials as bearing bushes.