Tribological behaviors of (Ca, Mg)-Sialon under lubricating of polyols

The friction and wear behaviors of (Ca, Mg)-Sialon/GCr15 steel couple under dry sliding and lubrication of water and polyols (ethanediol, 1,3-butanediol, 1,4-butanediol and propanetriol) were investigated by an SRV tester in a ball-on-disk configuration. It was found that as compared with dry sliding, all the polyols not only reduced the friction coefficient of (Ca, Mg)-Sialon sliding against GCr15 steel significantly but also reduced the wear volume considerably (1-2 order). The lowest friction coefficient 0.06 was recorded as lubricated by ethanediol. The wear volume of (Ca, Mg)-Sialon sliding against a bearing steel under the lubrication of the tested polyols could be ranked as below: ethanediol > 1,4-butanediol > 1,3-butanediol > propanetiol. It was supposed that the performance of polyols was correlated with their molecular structures. Namely, the longer the chain length and/or the bigger the number of hydroxyl radicals, the smaller the wear volume of (Ca, Mg)-Sialon. Electron probe microanalysis (EPMA) of the worn surfaces indicated that the wear mechanisms of (Ca, Mg)-Sialon was dependent on the friction and wear test conditions. Fourier transform infrared spectroscopic (FT-IR) analysis of the worn ceramic surface showed that tribochemical reactions between (Ca, Mg)-Sialon and polyols was involved in the friction process, which led to the decrease in the wear volume and friction coefficient of (Ca, Mg)-Sialon sliding against GCr15 steel.