Microstructures and properties of Cu-10Sn oil bearings reinforced by Al2O3 nanoparticles

Abstract

Using Sn and Cu-Al powders as raw materials, three oxide dispersion-strengthened (ODS) Cu-10Sn alloy powders with different Al2O3 mass content (0.42%, 0.85% and 1.68%, respectively) were prepared by mechanochemical synthesis combined with diffusion alloying method. The oil bearings were then fabricated by pressing and sintering. The effects of Al2O3 on microstructures and properties of the powders and the oil bearings were investigated. The results show that Al2O3 nanoparticles with sizes of about 5 nm are uniformly distributed in the ODS Cu powders. The content of Al2O3 nanoparticles has no effect on the distribution uniformity of tin during the diffusion process. And three ODS Cu-10Sn alloy powders with homogeneous tin distribution are prepared. However, the temperatures of forming liquid phases in the ODS Cu-10Sn alloys decrease with increasing Al2O3 content. This affects the sintering behaviors and mechanical properties of oil bearings. Increasing Al2O3 content also has a significant promoting effect on the precipitation of Sn-rich particles. In order to synergize the solid solution strengthening of tin and the dispersion strengthening of Al2O3 nanoparticles, the content of Al2O3 in the ODS Cu-10Sn alloys will not exceed 0.85%. The ODS Cu-10Sn oil bearings with 0.42% Al2O3 sintered at 900 °C have the best comprehensive properties, with uniform radial and axial shrinkage, oil content of 19.1%, radial crushing strength of 284 MPa and micro-hardness of 142 HV.