Effects of sliding speed on tribological behaviors and tribochemical reactions of alumina in HFC-134a gas

The effects of sliding speed on tribological behaviors of alumina (Al2O3) f riction pairs in 1,1,1,2-tetrafluoroethane (HFC-134a) gas at 5.2 x 10(3) Pa were investigated by using a ball-on-disk tribometer. Wear tracks on the d isk specimens were analyzed in situ by X-ray photoelectron spectroscopy (XP S) to identify tribochemical products. It was found that friction and wear properties of Al2O3 in HFC-134a strongl y depended on sliding speed. The friction coefficient sharply increased whe n the speed exceeded 0.15 m/s. For the disk specimens, no obvious wears wer e observed. The specific wear rate of the ball showed a maximum value when speed was 0.15 m/s. The results of XPS analysis identified that tribochemical films, mainly com posed of fluorinated compounds, were formed on the tracks. In addition, it was also found that the sliding speed affected the amount of the formed flu orinated compounds. More AlF3 was formed under lower speed and relative mor e organic compounds were formed under higher speed. The reason for sliding speed affecting the friction and wear properties of Al2O3 is that the diffe rent products formed by tribochemical reactions. (C) 2001 Published by Else vier Science B.V.