Study On The Tribological Properties Of Modified Lubricants For Wire Ropes In A Mine Hoist

With the mining of ultra-deep mines,the working environment of multi-layer winding hoisting wire ropes as load-bearing components is complex and harsh.The lubricating oil for the wire rope is extremely easy to fail and aggravates the friction and wear,which directly affects the service life of the wire rope and the safety and reliability of the mine lifting system.Therefore,it is of great significance to further improve the lubricating ability on the basis of existing steel wire rope lubricants and then reduce friction and wear between wire ropes.The commercial steel wire rope lubricant named IRIS was studied as basic research object in this paper.The preparation and characterization of different types of layered solid lubricant additives,the dispersion stability of these additives in IRIS,and the tribological properties of these additives dispersed lubricants were explored.First,octadecylamine functionalized graphene oxide(ODA-GO)was synthesized by means of dehydration condensation,and then reduced by hydrazine hydrate to obtain reduced octadecylamine functionalized graphene oxide(ODA-r GO).Then,FT-IR,XPS,FESEM,TEM,XRD,Raman and TG analytical methods were used to analyze the chemical structure,surface morphology,interlayer spacing,defects and thermal stability of the modified graphene-based materials.Subsequently,lanthanum stearate(La-St),a layered solid additive containing rare earth element lanthanum,was prepared.Its chemical structure,surface morphology and thermal stability were analyzed through FT-IR,XRD,SEM and TG.Afterwards,the dispersion stability of the above mentioned solid additives in IRIS was observed statically and then quantitatively analyzed by a UV-vis spectrophotometer,and the dispersion mechanism was revealed.Then,the load-carrying capacity,anti-wear and friction reduction properties of the modified oil with different dosages were evaluated using a four-ball tribotester.The wear mechanism of the wear scar and the lubrication mechanism were discussed.Finally,the effects of variable contact loads and sliding speeds on the frictional wear properties of wire ropes when lubricated with ODA-GO and La-St modified oil compared with IRIS were studied using a wire rope sliding friction-wear testbed.The results show that:the amidation reaction and nucleophilic substitution reaction occurred during the preparation of ODA-GO,and the latter was dominant.Lanthanum stearate had a disordered layered structure with good thermal stability.Dispersion force dominates the dispersion stability of solid additives in non-polar lubricants,so ODA-GO with higher grafting density of octadecyl chains has the best dispersion stability in IRIS,followed by lanthanum stearate,and ODA-r GO with lower grafting density of alkyl chains performs worst.Furthermore,with the help of oleic acid,the dispersion stability of La-St in IRIS can be significantly improved.ODA-GO,ODA-r GO and La-St modified oils all can improve the extreme pressure,anti-wear and anti-friction performance of IRIS,but the graphene-based oil performs better under the same dosage than La-St.ODA-r GO shows a better anti-wear and anti-friction ability than ODA-GO under their respective optimal additive amount.Nano-solid additives would be adsorbed onto the friction contact surface,fill the damaged area and reacts tribochemically with the substrate to form a lubricating film containing Fe₂O₃,Ca CO₃and so on,thereby reducing friction and wear.The friction coefficient between wire ropes shows a downward trend with the increase of load and sliding speed lubricated with modified oils.However,the wear increases with the increase of the load and decreases with the increase of the sliding speed.When the contact load reaches to 230N,dry friction occurs between the wire ropes lubricated with IRIS.ODA-GO modified oil has the best stability of the oil film,which is due to its friction coefficient curves are relatively stable within the range of measured loads and sliding speeds,and its anti-wear property is better under comparatively high load or low speed.On the contrary,La-St modified oil shows a better anti-wear performance under comparatively low load and high speed,but this characteristic is no longer obvious when the load is greater than or equal to 160N,and the friction coefficient curve has a trend of slow increasing with a larger average value under the same load.