Characterization and Wear Behavior of Tin-Bronze-Graphite Composite Prepared by Stir Casting

Abstract

In the present work, the stir-casting route was used to prepare composite samples of Cu-Sn base for self-lubricating bearing. Graphite represents the lubricating and reinforcing phase. The graphite particles were coated with copper by electro-less deposition in order to improve the wettability and facilitate its distribution in the molten metal during casting. Four samples with zero, 1, 3 and 5wt% of the coated graphite were cast. All samples were homogenized at 650°C for 3hrs. The influence of the added graphite on the microstructure and the properties of the composite was investigated. These properties were the hardness, the resistance to wear, and the friction coefficient. X-ray diffraction analyses indicates the avoidance of formation of the phases ε(Cu₃Sn) and δ(Cu₄₁Sn₁₁), which are hard and brittle. The microstructure revealed the uniform distribution of the particulates in the matrix system. Increase of 27% in Brinell hardness, reduction of 22-44% in the friction coefficient, and reduction of 47-49% in the wear rate were achieved by reinforcing the Cu10Sn with 5wt% of the coated graphite particles.