Effect of the surface nanocrystallization on tribological behavior of the Cu based bimetallic materials (CuPbSn)

Abstract

In this study, ultrasonic impact treatment was used to improve the tribological behavior of copper-based bimetallic materials that are used in internal combustion engine bearings and bushes. Bimetallic materials were obtained by coating three different CuPbSn alloys by sintering on the material surfaces of carbon steel substrate. After the sintering process, bimetallic materials were treated by ultrasonic impact process. As a result of the metallographic examination, sintered layers have uniform structure along the cross-section of the bimetallic materials. In addition, it was determined that the porosity of sintered materials decreased after the ultrasonic impact treatment. Due to the grain refinement and work hardening, higher hardness was obtained in the fine-grained layer. The hardness of the ultrasonic impact treated samples always higher than the untreated material. Because of the high surface hardness, ultrasonic impact treated samples showed higher wear resistance. The highest wear resistance was detected in the samples with the highest Sn content. Because Sn and Cu combine to form Cu3Sn intermetallic phase in Cu-Pb alloys and Cu3Sn increases the strength of the Cu-Pb alloys. Thus, increasing the Sn content in the Cu-Pb alloy resulted in the wear resistance increase. Furthermore, the formation of the SnO2 intermetallic phase on the sample surface has a significant effect on the wear resistance increase by preventing adhesion.