Influence of sintering pressure on microstructure and tribological properties of Copper–Tin composites containing graphite and MoS2

Abstract

Powder metallurgy was employed to facilitate self-lubricating composites using Cu-coated graphite powder, Cu-coated MoS2 powder and Cu-Sn alloy powder as raw materials. Investigations were conducted into how the sintering pressure affected the composites’ density, hardness, microstructure, and tribological properties. The results demonstrated that the porosity of the composites was reduced, the density increased from 6.46 g cm−3 to 7.32 g cm−3, the matrix grains were refined, and the hardness increased from 53.55 HV to 86.41 HV with an increase in sintering pressure from 30 MPa to 65 MPa. Additionally, raising the sintering pressure improved the interface bonding between the matrix and the solid lubricant graphite, MoS2. High sintering pressure was found to decrease the time needed for initial running-in and stabilize the volatility of friction coefficient. When the sintering pressure increased, the material’s friction coefficient first reduced and then increased while the wear rate first increased and then declined. Composites have good friction and wear qualities as a result of the production of a composite lubricating film containing graphite, MoS2, metal oxide, etc on the wear surface. Wear was brought on by the combined effects of abrasive wear, adhesive wear, material loss as a result of friction surfaces’ transverse crack expansion, and oxidation wear.