What are the advantages and disadvantages of different materials for plane bearings?

In mechanical structures and equipment systems, bearings are key components that enable relative motion, reduce friction, and support loads. While there are numerous types of bearings, plain bearings are a key type, widely used in low-speed, heavy-load, intermittent motion, and vibration or oscillation conditions. Compared to rolling bearings, plain bearings offer a simpler structure and greater adaptability, but their performance and lifespan depend significantly on the type and properties of the material used.
Plain bearings made of different materials have their own advantages and disadvantages in terms of load capacity, wear resistance, lubrication requirements, corrosion resistance, processability, and cost. To optimize material selection, extend service life, and improve efficiency, engineers and users must have a comprehensive understanding of the advantages and disadvantages of various materials. This article comprehensively introduces common plain bearing material types and their advantages and disadvantages, helping readers grasp the key points of material selection.

Copper-Based Alloys
Copper-based alloys (such as bronze, tin bronze, and lead bronze) are a long-standing bearing material, widely used for their excellent tribological properties. Advantages:
Good friction properties: The coefficient of friction between the copper alloy and the steel shaft is low, resulting in low starting resistance.
Excellent embeddability and conformability: Able to accommodate small particles and accommodate slight shaft misalignment.
Good thermal conductivity: Helps dissipate heat and prevents high-temperature seizure.
Good corrosion resistance: Suitable for humid or chemically exposed working environments.
Easy to combine with solid lubricants (such as graphite) to enhance self-lubricating properties.
Disadvantages:
High cost: Especially for high-tin bronze or alloys containing precious metals.
Limited strength: May wear faster under high loads or high speeds.
Heavy weight: Not ideal for lightweight structures.
Copper-based bearings are commonly used in low- to medium-speed environments with moderate loads and good lubrication conditions, such as motors, fans, and machine tools.

Powder Metallurgy Materials (Self-Lubricating Alloys)
Powder metallurgy bearings are made by compacting metal powders and then sintering them. They have a porous structure that can store lubricant, achieving self-lubrication. Advantages:
Excellent self-lubricating performance: No external lubrication system required, easy maintenance;
Low processing cost, suitable for mass production: Suitable for standard parts manufacturing;
Low operating noise, suitable for home appliances or office equipment;
Customizable shape: Complex structures can be formed through molds;
Stable friction coefficient, smooth operation.
Disadvantages:
Unsuitable for heavy loads or high-speed applications: Relatively low load capacity;
Porous structure easily absorbs impurities, leading to lubricant contamination;
High-temperature operation easily causes lubricant volatilization, losing self-lubricating properties;
Lower strength and impact resistance than forged or cast materials.
Suitable for small machinery with light loads, difficult lubrication, and confined working space, such as printers, fans, and micromotors.

Engineering Plastics (such as PA, POM, PTFE, and UHMWPE)
With the advancement of polymer material technology, an increasing number of engineering plastics are being used in plane bearings, especially in applications where lubricant is not permitted or in specialized operating environments. Advantages:
Good self-lubrication: Some plastics, such as polytetrafluoroethylene, inherently possess excellent friction-reducing properties;
Strong corrosion resistance and acid-base resistance: Suitable for use in chemical industry environments;
Lightweight and silent: Ideal for applications requiring lightweight or low noise levels;
Low cost and easy processing: Suitable for rapid, small-batch manufacturing;
Strong insulation: Suitable for electrical applications.
Disadvantages:
Limited load capacity and temperature resistance: Susceptible to deformation or aging under high temperatures or heavy loads;
Poor dimensional stability: Susceptible to expansion due to humidity and temperature;
Low wear resistance compared to metal materials, resulting in a shorter lifespan;
Unsuitable for long-term continuous operation: Heat accumulation can easily lead to performance degradation.
Suitable for clean, lightly loaded, and noise-critical working environments, such as medical equipment, food processing machinery, and packaging equipment.

Composite materials (polymer + metal, metal + solid lubricant)
Composite bearings enhance overall bearing performance by combining different functional materials, such as a metal matrix with a polymer layer, or a metal with a solid lubricant such as graphite or molybdenum disulfide. Advantages:
Excellent overall performance: Combining the strength of metal with the self-lubricating properties of polymer/solid lubricants;
Long service life: Stable operation even under dry or boundary lubrication conditions;
Low coefficient of friction: Suitable for high-frequency reciprocating motion;
Strong wear resistance and good friction stability;
Some materials can be used for dry friction or grease lubrication.
Disadvantages:
High cost: Complex material compounding and processing;
Limited operating adaptability: Not all composite structures are suitable for high loads or temperatures;
Difficult maintenance: Some composite structures cannot be repaired and must be replaced.
Widely used in applications requiring high wear and impact resistance, such as construction machinery, agricultural equipment, railway equipment, and automotive chassis components.

Cemented Carbide and Ceramic Materials
In some special operating conditions, such as high temperatures, high speeds, and highly corrosive environments, conventional metals and plastics are insufficient. In these cases, high-performance materials such as cemented carbide (such as tungsten carbide) or ceramics (such as silicon nitride) are used. Advantages:
Wear resistance: Can be used in harsh conditions such as sand, corrosion, and high pressure;
High temperature resistance: Remains stable in environments up to 800°C;
Excellent corrosion resistance: Suitable for chemical and marine environments;
Long service life, virtually maintenance-free;
Suitable for dry friction or low-lubrication applications.
Disadvantages:
Material brittleness and poor impact resistance;
Processing difficulty and high cost: Requires specialized equipment for forming and surface treatment;
Heavy weight (carbide) or demanding assembly conditions (ceramic);
Suitable for damage during installation, requiring specialized personnel.
This type of bearing is commonly used in applications such as aerospace, power generation equipment, offshore platforms, and high-temperature furnaces, and is a high-tech bearing product.

Metal Matrix + Coated Bearings
Some plane bearings utilize a steel or aluminum alloy substrate coated with specialized materials, such as PTFE, ceramic, or metal spraying, to enhance surface friction and corrosion resistance. Advantages:
Improves wear resistance and lubrication performance;
The surface coating can be customized to meet specific requirements: varying thicknesses and materials can achieve specific functions;
Relatively low cost: no need to use high-priced materials throughout;
High substrate strength and reliable structure.
Disadvantages:
Coating thickness is limited, resulting in a limited wear life;
Performance degrades sharply after the surface layer falls off;
The manufacturing process is complex and requires high craftsmanship;
Unable to withstand excessive impact loads.
This structure is commonly used in medium-load applications, such as agricultural machinery, construction equipment, industrial conveyor lines, and other mid-range mechanical systems. VII. Material Selection Recommendations and Summary
In practical applications, the following factors should be considered when selecting a plane bearing material:
Load Size and Operating Speed: Metals or composite materials are preferred for heavy loads or high speeds.
Lubrication Requirements: Copper alloys are recommended for good lubrication, while powder metallurgy or engineering plastics are preferred for difficult lubrication.
Ambient Temperature and Humidity: Avoid plastics for high-temperature applications, and consider corrosion protection for low-temperature or hot and humid environments.
Cost Budget: Powder metallurgy is preferred for large-scale production, while composite materials or coatings can be used for small-scale production.
Special Functional Requirements: For requirements such as electrical insulation, magnetic insulation, and chemical resistance, ceramics or specialty plastics may be selected.
Each material has its own suitable operating conditions and limitations; no single material is suitable for all applications. Scientific and rational material selection is key to ensuring equipment reliability, extending bearing life, and reducing operating costs.

Conclusion
Although plane bearings have a simple structure, their performance is highly dependent on the material properties. A thorough understanding of the performance advantages and disadvantages of different materials, such as copper-based alloys, powder metallurgy, self-lubricating plastics, composite materials, ceramics, and coatings, allows for a sound bearing selection plan tailored to actual operating conditions.