| TiAl-Ag self-lubricating composites,for the excellent united property of small specific volume,high specific strength and oxidation resistance,etc.,can be used to fabricate the lightweight structure components under the service conditions of high temperature and heavy loading.TiAl-Ag composites are expected to apply in the industrial domains of aviation,spaceflight,automobile and metallurgy,etc.Currently,the lubricating behavior of soft metal Ag is mainly concentrated on the experiment researches.The main explanations on lubrication mechanism remain the formed concept of lubricating film.Hence,it needs to obtain the deepen comprehensions of lubricating film composition,structure feature,forming mechanism and effect factors.It also needs to further execute the deepen theory researches on silver migration,film formation,film morphology,Ag distribution area,lubricating behavior and failure mechanism,as well as enhancement mechanism.Hence,in this paper,the one/binary interpolation theories are adopted to establish the prediction models of tribological properties in the fields of load-temperature-time.The analysis theories of Hamilton & Hashin and hardness calculation,as well as material plastic deformation are adopted to study the evolution mechanism of frictional layers,especially the migration behavior and forming film of Ag.The united methods of principal component cluster theory,finite stress model and advanced microscopy testing are used to study lubricating behavior and enhancement mechanism of lubrication film containing massive Ag and MWCNTs(Multiwalled Carbon Nanotubes).The friction and wear behaviors of TiAl based composites are evaluated by fabricating the hammer blocks of centrifugal mills,in order to verify on the experimental results of lubrication behavior.The main conclusions could be summarized as follows.1)The spark plasma sintering technology is used to prepare TiAl-Ag composites.The effect of load-temperature on the friction and wear property of TiAl-Ag is studied.The results show that at 12N-450?,the small friction coefficient and less wear rate are related to the surface morphology of friction layer,and distribution area of Ag on wear scar,which also are closely related to the mechanical and physical properties of friction layer.2)The united methods of Newton interpolation and bivariate rational interpolation are adopted to establish the prediction models of tribological property at the effect of load-temperature-time.The results show that the prediction models could be used to calculate friction coefficient and wear rate,and the high prediction accuracy is mainly attributed to the outstanding lubrication property of friction layers.3)The united methods of Hamilton & Hashin model and experimental testing are adopted to study the structure evolution and constitution variation of friction layers,as well as the basic properties of lubrication film.The results show that the organizational structures and mechanical physics properties of friction layers are significantly changed at the effect of mechanical and thermal stresses.During the sliding wear process,solid lubricant Ag is squeezed out of TiAl-Ag composite,spread out to wear scar,and form lubricating film,leading to the excellent friction and wear property,and the small friction coefficient and less wear rate.4)The theory of principal component cluster is used to establish the computing model of Ag distribution area,in order to study the existed relationship between silver distribution area and tribological property.The results show that friction coefficient and wear rate obtained by prediction method are approximately equal to their tested values,and the similar variation tendency is also found.In addition,the excellent plastic ductility of silver improve the continuous plastic deformation of lubricating film,leading to the improving of lubrication behaviors.5)The methods of numerical calculation,finite simulation and experiment test are adopted to study the local failure mechanism of friction layers and the enhancement mechanism of lubricating behaviors.The results show that the shearing strength of lubricating film is significantly improved by MWCNTs,and the local damage of lubricating film is lowered,leading to the acquiring of excellent tribological property.The engineering evaluation is used to enhance the lubricating behavior of TiAl based composite,and obtained the consistent results of experiment research and theory analysis. |
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