Study On Solid Lubrication Modification Of W/MO Films And Their Tribo-chemical Mechanism

This paper aims to learn the typical tribological properties of non-ferrousmetallic materials. Ion beam assistant deposition （IBAD） technology was used toprepare the tungsten, molybdenum and tungsten-molybdenum mixing films. And lowtemperature ion sulfuration was used to sulfidize the tungsten and molybdenum films.The friction coefficients of the tungsten and molybdenum films were tested by MS-T3000friction and wear testing machine. The boundary tribological behaviors of thethree non ferrous metallic films in the lubrication of ZDDP, MoDTC were examinedon the SRV wear testing machine. Some surface analysis techniques such asSEM+EDS, XRD, nano-indentation hardness and XPS were applied to analysis themorphologies, micro structures, mechanical properties and the element combinationstates of the films. Triboligical behaviors of the sulfilized W and Mo films as well asthe tribological properties and mechanisms of the three films in the lubrication ofZDDP and MoDTC were studied. The results are as follows:（1） Tungsten, molybdenum and tungsten-molybdenum mixing films weresuccessfully prepared on the316L stainless surface by IBAD technology. Thethicknesses of the films were1μm,2μm and1μm. the hardnesses of the films were19.0GPa,11.0GPa and14.0GPa. And the elasticity moduluses of the films were390GPa,270GPa and270GPa.（2） During the process of sulfuration, molybdenum disulfide could be formed bythe reaction of Mo and S at the temperature of230℃. And the friction coefficient ofthe MoS₂film was0.4in dry friction, comparing with0.6on the mectallic film. Whilein the lubrication of PAO, the friction coefficient of the MoS₂film was0.06whichwas lower than on the Mo film. However, WS₂could not be formed at230℃.（3） In the boundary lubrication, the modified non-ferrous metallic films showedbetter tribological properities than316L substrate. The average friction coefficient ofthe three films was almost the same. It was0.11in the lubrication of PAO and0.08inthe lubrication of PAO+1%ZDDP, whereas it was0.06in the lubrication of PAO+1%MoDTC. However, wear volume of the three films was quite different. The wearvolumes on the tungsten film were almost the same in three lubricating conditionswith the value around3.7×10^-13m³. This was caused by the WO3formed on thesurface of tungsten film which can protect element W from reacting with thelubricating additives. Mo could react well with the lubricating additives, so the Mofilm had smaller wear volumes when adding the additives. And the smallest wearvolume was about2.4×10^-13m³occurred in the lubrication of PAO+1%ZDDP. Thetungsten-molybdenum mixing film also had smaller wear volumes when adding theadditives. But the tribological mechanism was somewhat different from it on themolybdenum film. On the tungsten-molybdenum mixing film, Mo promoted thereaction between the surface and additive, while W restrained it. The wear behaviorwas controlled by many chemical compounds.