Effect Of The Distribution State Of Spheroidal Graphite On The Microstructure And Friction Behavior Of Fe-G Series Metals

In this paper,the vertical-pull continuous casting technology was employed to prepare Fe-G series metal profiles.The size of graphite in the matrix is small,uniformly distributed but the quantity is different.The microstructure of the matrix was tailored by annealing heat treatment and austempering heat treatment,and the matrix of Fe-G metal composed by ferrite or a phase and y phase was obtained.The effects of the amount of spherical graphite on the microstructure,mechanical properties and tribological properties of Fe-G metal was systematically studied.First,the effect of the amount of spherical graphite on the microstructure of Fe-G metal was studied;Second,the samples were annealed to obtain Fe-G metals with same matrix but different amounts of spherical graphite.The effect of the amount of spherical graphite on the mechanical and wear behavior was studied;Finally,the effect of the amount of spherical graphite on the microstructure,mechanical properties and wear properties of Fe-G metals after austempering heat treatment was studied.The main conclusions are as follows:The amount of graphite in the Fe-G metal matrix is mainly affected by the cooling rate when the molten iron solidifies.A higher cooling rate can increase the amount of graphite.The as-cast matrix structure is composed of spherical graphite,pearlite and ferrite.As the amount of graphite increases,the content of pearlite increases and the structure becomes finer.This result is mainly determined by the competition between the area of the graphite/metal matrix interface and the cooling rate of the molten iron.The size of ferrite grains in the matrix decreases slightly as the amount of graphite increases after the ferrite heat treatment of Fe-G metals;The tensile strength increases with the amount of graphite,the friction coefficient decreases first and then increases,and the wear mechanism is abrasive wear.After the austempering heat treatment of Fe-G series metals,the matrix microstructure is composed of nanoscale a phase and high-carbon ? phase.As the amount of graphite increases,the size of the a phase decreases,and the high-carbon ? phase and its carbon content increase.This is because a larger amount of graphite is beneficial to ferrite nucleation and carbon atom diffusion.As the amount of graphite increases,the tensile strength of Fe-G metals after austempering treatment decreases first and then increases,which is mainly related to the amount of graphite,high carbon ?phase content and nanoscale ? phase.The friction coefficient of Fe-G metals after austempering treatment is basically the same as that after annealing,with the increase of the amount of graphite,it shows a trend of decreasing first and then increasing.The friction coefficient of Fe-G metals after austempering treatment is mainly affected by the amount of graphite and the metal matrix structure.During the reciprocating friction process,the metal matrix will undergo plastic deformation and eventually fall off to form abrasive particles,so the wear mechanism is abrasive wear.