Effect of Ni layer on the microstructure evolution and mechanical property of Cu-based bearing shell with aging treatment

Abstract

Cu-based bearing shell containing Ni layer was prepared by centrifugal casting. The effect of Ni layer on the microstructure evolution and mechanical property of Cu-based bearing shell with aging treatment was studied. The microstructure of the Sn-Sb-Cu alloy (ZChSnSbCu8-4) without aging is consisted of Sn-based solid solution and Cu6Sn5 phases which distributed uniformly in the matrix. After aging treatment, the grain boundary segregation is slowly disappeared, and the matrix transforms into a more uniform Sn-based solid solution. The Ni layer hinders the diffusion of Cu and Sn atoms at the interface, and suppresses the volume fraction increment of Cu6Sn5 phase during aging. The Cu6Sn5 phases are gradually coarsened during aging. The average bonding strength of Cu-based bearing shell with Ni layer is 70.3 MPa. After aging at 175 °C with 500 h, the bond strength is still higher than 50 MPa, which is greater than the specimen without Ni layer. The hardness of Cu matrix, Ni layer and Sn-Sb-Cu alloy decreases with increasing aging time. While the hardness of the region near the Ni/Sn-Sb-Cu interface increases from 47.5Hv to 88.4Hv during aging. The fracture surface of the samples after aging treatment is changed from intergranular/transgranular fracture mode to intergranular fracture mode. The change of the fracture mode is related to the coarsening and growth of Cu6Sn5 phases near the interface between Ni layer and Sn-Sb-Cu matrix.