| The high temperature self-compensation lubricating composites with microporous structure is a new type of self-lubricating composite material,which is prepared by infiltrating molten solid lubricants into the matrix under vacuum pressure.When working in high temperature condition,the solid lubricant is driven out from the pores of matrix under the coupling effects of friction heat and thermal stress,and the self-lubricating function was achieved with the lubricating film's formation.The lubricating performance of the composites depends on the precipitation of composite solid lubricant and it's component composition.Therefore,establishing the thermo-mechanical coupled driven model to study the precipitation mechanism of composite solid lubricants and analyzing the mechanism of film-forming,which has significant meaning for the design and preparation of the self-compensating lubrication composites with microporous structure.Based on the packing theory of porous media and microporous structure of high temperature self-compensating composites,the cell model was established.The temperature and stress field were calculated for the thermo-mechanical coupled problems in friction process.Aiming at the driving force of lubricant precipitation and using the theory of heat elastic mechanics,thermo-mechanical coupled driven model was established and it's influencing factors such as heating temperature,friction heat and friction were analyzed.The transient thermal and thermo-mechanical coupling analysis of infiltration-type self-lubricating composites were completed through the ANSYS Workbench,which got the the distribution and variation of temperature field and stress field and relative reason.Then,the change tendency of temperature,stress and strain of lubricant and matrix was analyzed.The change of the driving force was investigated under the effect of different factors such as heating temperature,friction heat,extrusion pressure of hole's deformation.The simulation results indicated that the heating temperature was contributed to the driving force,and the frictional heat should be taken into account after continuous heating.Compared to heating temperature,friction heat had significant role in promoting the driving force and the extrusion stress of deformation of hole had less influence on it.The lubricant was precipitated to the friction interface due to the affects of heating temperature,friction heat and stress,anddeformation extrusion.The component design of solid lubricant was carried out based on the compatibility and solubility of lubricants and matrix material,through the wetting experiment and analysis of empirical formula,it's best component composition was: lead65tin35+12~18%silver+0.2~0.3% rare earth such as yttrium.The infiltration of matrix with lubricants was achieved by high frequency electromagnetic induction melting process,and thus the infiltration-type M3/2/TiC self-lubricating composite at high temperature was prepared.The friction and wear properties of the infiltration-type self-lubricating composite at high temperature was studied by pin-disc friction and wear tester at high temperature,and the wear surface composition,morphology and structure was analyzed by scanning electron microscopy(SEM),photoelectron spectroscopy(EDXA)and X-ray diffraction(XRD).The results showed that the lubricating elements were diffused or squeezed out of the matrix,forming a thin solid lubricating film consisting of lead,tin,silver,yttrium et al on the friction surface.The lubrication performance of the composite was relatively improved by adding0.25% yttrium oxide to the lead65tin35-12% silver lubricants.The film-forming mechanisms of high temperature self-compensation lubricating composites were analyzed based on the analysis of SEM topography. |
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