Guide to Common Bearing Materials Selection

The selection of bearing materials directly impacts the reliability and service life of mechanical systems, requiring alignment with operational conditions (load, speed, environment). Mainstream bearing materials are categorized into three types: metallic, nonmetallic, and porous metallic materials. Below is a technical analysis of their characteristics and application scenarios.

I. Metallic Materials: Core Choice for High-Strength Load Bearing

1. Bearing Alloys (Babbitt Alloys/White Metals)

• Composition & Structure: Soft-matrix alloys with tin or lead as the base, containing hard grains of antimony-tin (Sb-Sn) and copper-tin (Cu-Sn).
• Key Advantages:
  • Soft matrix provides high ductility and conformability, while hard grains enhance wear resistance;
  • Exceptional embedability (allows impurity particles to embed, preventing journal scratches) and anti-adhesive wear properties;
  • Good thermal conductivity (reduces frictional heat accumulation) and oil adsorption (improves lubrication).
• Limitations:
  ▪ Low strength, requiring use as a thin coating (0.5–5mm) cast onto bronze, steel, or cast iron bearing shells;
  ▪ High cost, suitable for heavy-load, medium-speed applications with strict lubrication requirements (e.g., steam turbines, internal combustion engine main shafts).

2. Copper Alloys

• Typical Types:
  ▶ Tin Bronze: Excellent anti-friction properties, used in medium-speed heavy-load scenarios (e.g., marine propeller shaft bearings), but with inferior conformability to bearing alloys;
  ▶ Lead Bronze: High anti-seizure capability, suitable for high-speed heavy loads (e.g., aircraft engine bearings);
  ▶ Aluminum Bronze: High strength and hardness, weak anti-seizure, used in low-speed heavy loads (e.g., mining machinery bearings).
• Common Advantages: Higher hardness and load capacity than bearing alloys, offering better cost-effectiveness.

3. Aluminum-Based Alloys

• Technical Features:
  • Low density (about 1/3 of copper alloys), strong corrosion resistance, and high fatigue strength;
  • Can be manufactured as monometallic components or bimetallic structures (aluminum-based lining + steel backing), replacing some bearing alloys and bronzes.
• Applications: Automotive engine bearings, compressor bearings in medium-load high-speed scenarios.

4. Cast Iron (Gray Cast Iron/Wear-Resistant Cast Iron)

• Reinforcement Mechanism: Graphite flakes (lamellar or nodular) form a solid lubricating layer, adsorbing lubricants to improve boundary lubrication.
• Restrictions:
  ▪ Brittle with poor conformability, only suitable for light-load low-speed applications (e.g., agricultural machinery, hand tool bearings);
  ▪ Requires lubrication, unsuitable for impact load environments.

II. Nonmetallic Materials: Solutions for Special Environments

1. Polymer Materials (Plastics)

• Common Types:
  ▶ Phenolic Resin: High-temperature resistance (150℃), high strength, used in gearbox bearings;
  ▶ Nylon (PA): Good self-lubrication, shock absorption, suitable for dusty environments;
  ▶ Polytetrafluoroethylene (PTFE): Extremely low friction coefficient (0.04), corrosion resistance, operable without lubrication.
• Application Limitations:
  ▪ Poor thermal conductivity (1/200 of steel), requiring control of operating speed (≤0.5m/s) and pressure (≤3MPa);
  ▪ High linear expansion coefficient (10x that of steel), requiring fit clearances 2–3 times larger than metallic bearings;
  ▪ Low strength and prone to creep, unsuitable for precision clearance bearings.

2. Carbon-Graphite Materials

• Performance Advantages:
  • Self-lubrication relies on adsorbed water vapor and impregnated lubricants (e.g., metals, PTFE, molybdenum disulfide);
  • High-temperature resistance (over 600℃), corrosion resistance, suitable for vacuum or strongly corrosive environments (e.g., chemical pump bearings).
• Material Property: Higher graphite content leads to lower hardness and smaller friction coefficient (as low as 0.08).

3. Rubber and Wood

• Rubber: High elasticity, impurity adsorption, used in water-lubricated or polluted environments (e.g., wastewater treatment equipment bearings);
• Wood: Porous structure for oil impregnation, suitable for dusty environments (e.g., textile machinery, agricultural machinery bearings), requiring surface treatment for enhanced wear resistance.

III. Porous Metallic Materials: Optimal for Self-Lubricating Scenarios

1. Material Principle

• Manufacturing Process: Metallic powders (mainly iron/bronze) are pressed and sintered into a porous structure (porosity 10%–35%), saturated with oil before use to form oil-impregnated bearings.
• Lubrication Mechanism:
  ▶ During operation: Journal rotation and temperature rise release oil from pores to the friction surface;
  ▶ During shutdown: Capillary action draws oil back into the bearing, enabling periodic self-lubrication.

2. Typical Materials & Applications

• Porous Iron: Higher strength, used in medium-load low-speed scenarios such as mill liners, internal combustion engine camshaft bearings;
• Porous Bronze: Good wear resistance, suitable for electric fans, textile machinery, and automotive generator bearings (load ≤10MPa, speed ≤2m/s).
• Usage Recommendations: Regular oil replenishment for optimal performance, unsuitable for impact loads or high speeds (>3m/s).

Selection Decision Reference

Conclusion

1. Heavy load & high speed: Prioritize bearing alloys or lead bronze with forced lubrication systems;
2. Corrosive/oil-free environments: Use PTFE plastics or carbon-graphite materials, trading some load capacity for environmental adaptability;
3. Low-cost self-lubrication: Porous metallic materials are ideal for low-speed light-load scenarios.
   By comprehensively evaluating parameters such as load, speed, temperature, and environmental media, and combining material physical-mechanical properties with cost, the service life of bearings and operational reliability of equipment can be significantly enhanced.