Hot temperature tribological behavior of Mg-Zn-Gd alloy under graphite surfactant functionalized SN500

Abstract

The effect of SN500 and SN500 +G lubricants on the wear behavior of Mg-Zn-Gd alloy was studied. For this purpose, Mg-Zn-Gd alloy was produced by the stir casting method. The wear test was performed under 20, 40, and 80 N with a velocity of 0.5 m/s for 1000 m at different temperatures (25, 100, 150, 200, and 250 °C) under SN500 and SN500 +G lubricants. The results showed that in the presence of precipitates weight loss and wear rate were reduced. With the increasing load in all samples, weight loss and wear rate increased. The lowest wear rate was obtained at 250 under 20 N and was equal to 0.036 and 0.030 m3/m, and with an increase in the load to 80 N, it reached 0.044 and 0.042 m3/m for samples under SN500 and SN500 +G, respectively. It was also observed that lubrication of SN500 +G in all samples created better properties than SN500. The addition of graphite to SN500 also reduced the coefficient of friction. So that the friction coefficient of the tested sample under 80 N at 250 °C under SN500 has decreased by 15% compared to SN500 +G. The worn surfaces SEM micrographs of samples under SN500 +G lubricant show the presence of the mechanically mixed layer (MML) with the adhesive wear mechanism. With increasing load, the abrasion, delamination, and MML mechanisms were dominant, and a significant reduction of COF and wear rate were observed. At the high temperature and high loads, the crushing of precipitates and their orientation in the wear sliding was caused to dwindle applied load and prevented the activation of other wear mechanisms.