Blackening failure of poly-α-olefin impregnated porous polymide due to the splitting of lubrication oil catalyzed by iron

Abstract

AbstractLubrication failure accompanying with blackening phenomenon significantly reduces the long-running operational reliability of porous polymide (PPI) lubricated with poly-α-olefin (PAO) oil. Here, the effects of lubrication condition and counter-surface chemistry on the blackening failure of PAO impregnated PPI were studied through the comparison of the tribological tests against GCr15 steel ball and Al2O3 ceramic ball with and without PAO oil lubrication. Black products were found to be formed on the PAO impregnated PPI surface slid against steel ball or Al2O3 ball added with iron nano-particles, but be absent under the conditions without iron or PAO oil. Further analysis indicated that the iron-catalyzed splitting of PAO oil into small molecule alkanes and following the formation of black organic matter should be mainly responsible for the blackening phenomenon. Molecular dynamic (MD) simulations demonstrated that the iron facilitated the separation of hydrogen atom and the following broken of C-C bonds in PAO molecules, final resulting in the splitting of PAO oil.