Effect of ball-material ratio on Cu-Bi mixed powder and self-lubricating material properties

PurposeThis study aims to investigate the effects of ball-material ratio on the properties of mixed powders and Cu-Bi self-lubricating alloy materials.Design/methodology/approachCu-Bi mixed powder was ball milled at different ball-material ratios, and the preparation of Cu-Bi alloy materials was achieved through powder metallurgy technology. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were conducted to study the microstructure and phase composition of the mixed powder. The apparent density and flow characteristics of mixed powders were investigated using a Hall flowmeter. Tests on the crushing strength, impact toughness and tribological properties of self-lubricating alloy materials were conducted using a universal electronic testing machine, 300 J pendulum impact testing machine and M200 ring-block tribometer, respectively.FindingsWith the increase in ball-material ratio, the spherical copper matrix particles in the mixed powder became lamellar, the mechanical properties of the material gradually reduced, the friction coefficient of the material first decreased and then stabilized and the wear rate decreased initially and then increased. The increase in the ball-material ratio resulted in the fine network distribution of the Bi phase in the copper alloy matrix, which benefitted its enrichment on the worn surface for the formation a lubricating film and improvement of the material's tribological performance. However, a large ball-material ratio can excessively weaken the mechanical properties of the material and reduce its wear resistance.Originality/valueThe effects of ball-material ratio on Cu-Bi mixed powder and material properties were clarified. This work provides a reference for the mechanical alloying process and its engineering applications.