Effect of novel phosphazene-type additives on the tribological properties of Z-DOL in a steel-on-steel contact

The effect of hexakis(1,1,5-trihydroperfluoropentoxy)cyclotriphosphazene (X-100) and a novel synthetic bridged alkoxycyclotriphosphazene (denoted LA-2P) as additives in Z-DOL, a perfluoropolyether-type lubricant, on the friction and wear behavior of a steel-on-steel system was investigated. Thus, the friction and wear test of a steel disc sliding against the same steel counterpart ball was carried out on an SRV oscillating friction and wear tester. The chemical features of the worn steel surfaces were analyzed by means of X-ray photoelectron spectroscopy. The results indicate that both additives are effective in improving the tribological performance of Z-DOL and in preventing its catalytic decomposition. Z-DOL/LA-2P shows the best anti-wear ability. Moreover, both additives also increase the thermal stability of Z-DOL in the presence of AlCl3 as a catalyst. In particular, the Z-DOL/LA-2P mixture shows the highest complete thermal degradation temperature.