Applications of babbitt: where antifriction alloys are used

Babbitt is a group of antifriction alloys based on tin or lead with additions of antimony, copper and other elements. Its main purpose is service in plain bearings and bearing liners where a soft conformable surface is needed to retain lubricant and protect the shaft during normal operation.

Characteristics of babbitt

Babbitt combines a soft metallic matrix with harder inclusions. This helps the material conform during running-in, embed small contaminants, reduce the risk of scoring and work against a steel shaft when an oil film is present.

Babbitt is not a universal structural metal. It is usually applied as a thin layer on a steel, cast-iron or bronze backing. The backing provides stiffness and load support, while the babbitt layer works as the antifriction surface.

Types and grades of babbitt

Tin-based babbitts are usually more expensive, but they are better suited to critical bearings, higher sliding speeds and conditions where corrosion resistance and stable operation matter. Lead-based babbitts are less expensive and are used in lighter or more moderate duty where the bearing design allows it.

Calcium and other special babbitts are used in specific tasks where economy or particular service properties are important. The grade is selected according to load, shaft speed, temperature, lubrication, duty cycle and repair requirements.

In practice, grades such as B83, B16 and calcium babbitts may be encountered. The designation reflects the alloy composition, so one grade should not be replaced with another without checking the technical requirements.

Fields and areas of application

• Plain bearings. Babbitt is used as the working layer of liners and shaft supports in machines that require a stable oil wedge.
• Turbines, compressors and pumps. In power generation and industry, babbitt-lined bearings are used in large rotating equipment.
• Marine and railway machinery. Babbitt is used where repairability, damping and long-duration loading are important.
• Mining and metallurgical equipment. The alloy is used in heavy machinery, crushers, rolling mills and other sliding units.
• Automotive and agricultural machinery. In some diesel engine and machine assemblies, babbitt-lined bearings are used where the design is intended for this type of antifriction layer.
• Bearing repair. During liner rebuilding, the old layer is removed, the surface is prepared and a new babbitt layer is applied by the proper process.

Application limits

Babbitt requires proper lubrication, heat removal and bearing clearance. Overheating, contaminated oil, shaft misalignment or overload can destroy the layer quickly. Service life depends not only on alloy grade, but also on bearing design, casting quality, surface finish and maintenance.

For material mass calculations, see the separate article on babbitt weight.