Lead-based bearing alloy, Babbitt metal, is an alloy composed primarily of lead with additions of elements such as tin, antimony, and copper. It is also a type of bearing alloy characterized by a soft matrix with hard particles. The addition of tin forms hard SnSb particles and significantly dissolves into the lead to strengthen the matrix, thereby enhancing the strength and wear resistance of the lead-based alloy. The addition of copper forms hard Cu2Sb particles and prevents gravity segregation due to density differences.
Lead-based bearing alloys have lower strength, plasticity, toughness, thermal conductivity, and corrosion resistance compared to tin-based alloys, along with a higher friction coefficient. They are not suitable for bearings operating under severe vibration or impact conditions. However, due to their lower cost, they are still widely used in practice. Therefore, lead-based bearing alloys are commonly employed in the manufacture of medium and low-load medium-speed bearings.
Both tin-based and lead-based bearing alloys have relatively low strength (Rm = 60–90 MPa) and cannot withstand high pressures. In production, the centrifugal casting method is often used to cast them onto steel bushings, forming a thin and uniform inner lining. This process is referred to as "lining." After lining, a bimetallic bearing with a dual-metal layer structure is formed.