The Effect Of Interfacial State On The Mechanism Of Tangential Fretting Damage

Fretting damage directly threatens the maneuverability and reliability of mechanical equipment in the service life.At present,the most effective ways to reduce or suppress fretting damage are surface mechanical strengthening,surface heat treatment,surface lubrication,and etc.At present,the most commonly used methods are adding solid film or fluid lubricating to the interface to reduce wear.The most widely used solid lubricating materials are carbon-based materials and transition metal sulfide.Therefore,it is necessary to study the fretting wear characteristics of diamond-like carbon-based and molybdenum disulfide films.It not only enriches the theoretical research of films'fretting,but also provides some reference for practical engineering application.This study was carried out on a high precision multifunctional fretting wear tester.The fretting behavior and wear mechanism about two kinds of solid films under different conditions were studied by using spherical/surface contact.The morphology of the wear surfaces was analyzed by means of scanning electron microscope,electron energy spectrum,X-ray photoelectron spectroscopy and Raman and so on.The effect of operating conditions on the fretting behavior of the solid film was studied.The results of the paper were as follows:1?The working parameters?normal load and displacement amplitude?affected the fretting state of the solid film.With the increase of displacement amplitude,the fretting regions of DLC film/GCr15 ball and MoS₂ film/GCr15 ball changed from partial slip regime to slip regime when the load was constant.And the friction coefficient in the stabilization period was increased,but its growth rate fell.The friction coefficient was reduced with the load increased.In the partial slip regime,the fretting damage was mainly caused by adhesion wear and slight abrasive wear.In the sliding regime,the wear mechanism of the film was mainly abrasive wear and oxidation wear.The change of displacement amplitude had a more obvious effect on the MoS₂ film,because of the lamellar structure of MoS₂ is prone to slip.2?The effects of dual materials on the fretting state of solid films are as follows:When F_n=20 N,D=45?m,choosing the 10 mm diameter of GCr15,Al₂O₃,SiC and Si₃N₄ balls as dual spheres,the fretting regions of DLC films were located in the slip regime,slip regime,mixed regime,and mixed regime,respectively.The fretting regimes of MoS₂ film with these four pairs of balls were all located in the slip regime.It showed that the high-hardness ceramic ball increased the wear of the DLC film and promoted the formation of MoS₂ films'plastic flow to reduce wear.Among the four dual balls,DLC film/Al₂O₃ ball showed lowest friction coefficient better stability.The SiC and Si₃N₄groups damaged the DLC film.The variation of the friction coefficient between the four dual balls with the MoS₂ film was small,and the difference was little.On the whole,the friction performance of MoS₂ film groups was more stable and the friction coefficient was lower than DLC film.3?The changed load,displacement amplitude and dual ball had effects on the wear mechanism of the film's oxidation behavior and the transfer of the third body,and the formation of the plastic flow layer on the interface.Thorough DLC films'graphite and MoS₂ films'plastic flow formation,the wear were further reduced.4?The type of lubricating oil affects the fretting characteristics of the film.When F_n=20 N,D=45?m,the fretting regime of the two films were in the mixed regime,while lubricated the other three lubricating oils?[BMI_m][PF₆],MACs and PFPE?were located in the slip regime.DLC film/MACs synergistic lubrication system showed good wear-reducing and wear-resistance characteristics,so does the MoS₂ film/[BMI_m][PF₆].Film lubricated with silicone oil showed adhesion wear,oxidation wear and large area peeling off.The boundary lubrication ability of silicone oil is poor,and the surface tension is small,and it is easy to cause lack of oil on the interface.The active elements in[BMI_m][PF₆]had a tribological chemical reaction with the elements on the contact surface,forming a compound boundary lubricating film,which effectively inhibited the contact of the grinding pair.The MACs easily formed a physical adsorption film.The wear resistance of PFPE was mainly due to the reaction with the element in the friction interface to form a dense protective layer.