Effect of load and temperature on wear and friction behavior of submicron alumina particle reinforced 6061-aluminum alloy using a solid lubricant

Abstract

Tribological behavior of A1 6061 alloy reinforced with 20% submicron (0.7 μm) Al2O3 particles was examined under dry and lubricated conditions at temperatures ranging from 25°C to 300°C. Wear tests were performed against AISI 4041 steel counterface material at selected loads using a pin-on-disk type apparatus using graphite and molybdenum disulfide burnished powders as solid lubricants. Under dry conditions, the wear resistance of the composite was characterized by two regimes namely mild and severe wear at all temperatures. However, the critical load for severe wear was found to decrease with increase in temperature, indicating decrease in wear resistance with increase in temperature. The worn surfaces were characterized by abrasion, delamination and adhesion in mild, transition and severe wear regions respectively at room temperature. However, at elevated temperatures, matrix softening of the composite was found to be dominant mechanism of wear in addition to particulate fracture. Lubrication using graphite was found to be effective only at room temperature and upto 30N normal load. At high temperatures, severe wear rates and high coefficients of friction resulted under graphite lubrication because of absence of vapor and moisture at high temperature required for superlubricity of graphite. When molybdenum disulfide was employed as solid lubricant, the wear rates and coefficients of friction were drastically reduced when compared with dry conditions at respective loads and temperatures. The composite worn surfaces under MoS2 lubrication were characterized by smooth surface covered with MoS2 layers evident by EDS analysis.