Research On Preparation And Microstructure Of Iron Matrix/SiC Ceramic Composites

Metal-matrix ceramic wear-resistant composite materials was the hotspots of research on wear-resistant materials at home and abroad recently and had broad prospects for development.Traditional high-chromium cast iron wear-resistant material used as a common material for grinding mills,grinding discs and other wear parts of power mills in domestic power plants can no longer meet the requirements of the enterprise for the life and efficiency of coal mills.At present,ceramic-reinforced metal matrix composites had been successfully applied to wear-resistant parts in power,cement,and chemical industries in foreign countries.Their service life was 2.5 to 3 times longer than that of ordinary high-chromium alloys or surfacing alloys.The development of domestic wear-resistant composite materials is slow,and it was still in the experimental research stage.Therefore,the research of metal-matrix ceramic composite materials is of great significance.In this test,SiC ceramics were used as the reinforcement,and iron alloys were used as the base metal.The pressureless solid-state sintering process was used firstly,SiC ceramic preforms with a certain porosity and high temperature strength was prepared under the process parameters of molding pressure of 30MPa,sintering temperature of 1300°C and holding time of 60 min.Based on this,pressureless infiltration process was used to prepare iron-based/Si C composites with different Ti content,Si content and particle sizes.Optical microscopy,SEM,EDS,and XRD techniques was used to study the microstructure,phase composition,microstructure defects,element distribution and infiltration process of the composites.The SiC preform with certain strength and porosity was successfully prepared by a pressureless solid-phase sintering process.With the increase of the mass fraction of Ti in the preform,the porosity of the SiC preform decreases,the strength increases,and the densification progresses,and new phases such as SiO2 and TiO2 appear.Iron-based/SiC ceramic composites with different Ti content were prepared by pressureless infiltration.With the increase of the mass fraction of Ti,the number of uninfiltrated voids in composites decreased and the density of composites became denser.With a certain Ti mass fraction,as the depth of infiltration increased,inter-diffusion of elements and chemical reaction weaken,and the effect of iron alloy infiltration weakened.The composite material mainly consists of metal matrix phase,SiC ceramic particle phase,and Ti-rich island phase.After infiltration,diffusion and mutual reaction,new phases such as C,FeSi,and TiC were formed.All elements had different degrees of mutual diffusion,of which C,Cr elements were more diffusive.The main defects in composites were microcracking around Si C ceramics and non-impregnated holes left in the metal region.Microcracks are divided into transverse cracks and vertical cracks.The mechanism of various defects is different.When the mass fraction of Si is 15wt.%,the iron alloy solution can completely infiltrate the ceramic preform after 6mm.In addition to the basic phases such as SiC,FeSi,Fe-Si-C and Cr₇C₃,there was no single-phase graphite C in the composite material.However,there was a single elemental Si phase.Elemental Si was mainly located at and near the interface of the composite material.The elemental Si at the interface changed the phase composition of the composite interface,which greatly reduced the degree of interface reaction.When the Si C particle size was 500 mesh,the agglomeration phenomenon of SiC ceramic existed in the local area of the iron-based/SiC ceramic composites.When the SiC particle size was 150 mesh,there were many transverse crack defects in the composites.When the grain size was 300 mesh,the SiC particles in the composites evenly distributed without obvious defects.