Preparation And Properties Of In-situ TiC Reinforced Titanium Matrix Composites

Titanium and titanium alloys have attracted wide attention due to their high specific strength,high specific modulus and high temperature resistance.However,low hardness,poor wear resistance and high cost of preparation limit their development in the civil field.In this paper,In order to prepare titanium matrix composites with excellent comprehensive properties and low cost,in-situ TiC reinforced titanium matrix composites were prepared by in-situ reaction using acetylene carbon black as carbon source and pure titanium as matrix by hot pressing sintering technology.Titanium matrix composites with different volume of TiC reinforcement phases were prepared by different ball milling process and sintering temperature.The mechanical properties and friction and wear properties of the composites were tested.XRD,SEM,EDS were used to analyze the morphology and distribution of raw materials,phase composition and microstructure of composites,fracture morphology and microstructure of wear surface to explore the effects of ball milling process,volume fraction of reinforcement phase and sintering temperature on the micro structure,mechanical properties and friction and wear properties of composites.The results were showed as follow:(1)The ball milling speed and ball milling time have great influence on the micromorphology of raw material powder.With the increase of ball milling speed,the carbon black disperses more uniformly in the mixed powders,and the plastic deformation of titanium powders becomes more serious.With the increase of milling time,the carbon black disperses more uniformly in the mixed powders,and the plastic deformation of titanium powders becomes more serious.When the ball milling time is too long,the carbon black in the mixed powders will be reunited again,which is not conducive to the dispersion of carbon black.The optimum ball milling process is 300 r/min ball milling speed and 8 h ball milling time.(2)Sintering temperature has a great influence on the microstructure and mechanical properties of composites.With the increase of sintering temperature,TiC tends to bond together and the mechanical properties of the composites are improved.The densification,hardness,flexural strength and compressive strength of the composites sintered at 1600℃ are the highest.(3)The content of TiC has a great influence on the microstructure and mechanical properties of the composites.With the increase of TiC volume fraction,the TiC reinforcement phase is connected from small particles to dendrites,and then from dendrites to large blocks and irregular polygons.When the volume content of TiC is 1%,TiC is granular and its diameter is between 1～5 μm;When the volume content of TiC is 20%,TiC is block and irregular polygon,and its diameter is between 50～70 μm.(4)With the increase of TiC content,the mechanical properties of the composites are improved.When the volume fraction of TiC is 20%,the Vickers hardness of the composites reaches 8.7 GPa.The bending strength is 619 MPa.The yield strength is 1875 MPa,and the eompressive strength is 2134 MPa.The yield strength and compressive strength of the composite with 10%TiC volume fraction reached 1583 MPa and 2065 MPa respectively,and the deformation rate is kept at 17%.The composite material maintains both high strength and good deformation ability.(5)The wear resistance of composites increases with the increase of TiC content.When the volume fraction of TiC is 20%,the composites have excellent tribological properties.When the sliding friction speed is 5 m/s and the normal load is 70 N,the coefficient of friction is 0.366,and the wear rate is 1.801 × 10-6 mm3/N·m.(6)When there is no TiC or less TiC content,the worn surface of the composites is easy to be ploughed by the micro-convex body of the grinding disc,and the peeling and transfer of the grinding disc will cause abrasive wear on the worm surface.With the increase of TiC content,the surface hardness of the composites increases,and the hard TiC reinforcement phase prevents the ploughing damage of the grinding disc to the worn surface.TiC reinforcement phase and Ti matrix bond well,and the hard TiC phase hinders the expansion of spalling and plastic deformation.The Fe transferred from the grinding disc and Ti matrix are oxidized under friction heat to form an oxide film with a thickness of about 0.5 μm,which plays a lubricating role.As a result,the wear resistance of titanium matrix composites is improved,and the coefficient of friction and wear rate of the composites decrease.