The Research On Preparation And Properties Of Carbon Fiber Reinforced Ceramic Metal Matrix Composites

The development of the transport industry towards high speed and high capacity puts forward demanding requirements for the strength and toughness of friction materials for braking devices.At present,the widely used friction materials are cast metal and powder metallurgy materials,which have the disadvantages of low friction coefficient at high temperature and high speed,easy to produce noise during braking,easy to damage the dual parts,and large weight.It is difficult to meet the needs of emergency braking under high speed and heavy load transportation in the future.Therefore,for high-speed and heavy-duty braking conditions,there is an urgent need for friction materials with high temperature resistance,wear resistance,moderate friction coefficient,light weight and good strength and toughness.Carbon fiber reinforced ceramic matrix composite represented by C/C-SiC composite have low density,high temperature resistance,wear resistance and corrosion resistance,which are new friction materials available for high-speed and heavy-duty transportation in the future.However,in the high-speed braking process,the residual phase in carbon fiber reinforced ceramic matrix composite easily leads to high frequency vibration,resulting in unstable braking.The matrix of carbon fiber reinforced ceramic matrix composite is still brittle ceramics,although there is continuous carbon fiber toughening in carbon fiber reinforced ceramic matrix composite,and the cracks generated by loading will expand singly in a brittle matrix.These problems limit the further development and engineering application of carbon fiber reinforced ceramic matrix composite.In view of the above problems,this paper aims to optimize the performance of carbon fiber reinforced ceramic matrix composite.The ductile copper alloy is introduced into the matrix of the composite by reactive melt infiltration(RMI),to improve the strength and toughness of the composite and optimize the friction and wear properties of the composite.To verify the feasibility of the idea,the wettability and reactivity between Cu-based alloy and porous C/C preform were studied,the possible reactions in the system were discussed,and the thermodynamic feasibility of the reaction was analyzed.Based on the RMI method,carbon fiber reinforced ceramic metal matrix(C/C-SiC-Cu,C/C-TiC-Cu and C/C-SiC-TiC-Cu)composite were prepared,respectively.The phase structure and microstructure of the composite were characterized,and the mechanical properties and friction and wear properties of the composite were investigated.Firstly,the typical carbon fiber reinforced carbon and silicon carbide dual matrix(C/CSiC)composite in carbon fiber reinforced ceramic matrix composite were studied.The C/CSiC-Cu composite were prepared by the RMI method by optimizing the Si powder infiltrator was optimized to Si-Cu alloy with low melting point.The residual Si in C/C-SiC composite was transformed into the Si-Cu phase to improve the strength and toughness of C/C-SiC-Cu composite and optimize the friction and wear properties of composite.It was found that the phase composition of the C/C-SiC-Cu composite was C,Cu3Si,Si and Cu.The addition of copper alloy improved the problem of residual Si in the composite,and significantly improved the bending strength and fracture toughness of the composite.The values were 258.75±20.01 MPa and 13.55±2.91 MPa·m1/2,respectively.Friction and wear experiments show that the friction coefficient of the composite tested with Al2O3 and Si3N4 balls is stable,while the friction coefficient of the composite tested with 440C steel balls fluctuates greatly.Secondly,the SiC matrix in C/C-SiC composite was optimized by replacing the ceramic matrix.The low melting point Ti-Cu alloy was designed as infiltrator to prepare C/C-TiC-Cu composite.The SiC ceramic matrix in C/C-SiC composite was optimized to TiC ceramic matrix with better performance.At the same time,copper alloy was introduced into the composite to improve the strength,toughness and friction and wear properties of the composite.It was found that the phase composition of the C/C-TiC-Cu composite was C,TiC,Ti3Cu4,TiCu4 and Cu.The mechanical properties of the composite were affected by the Cu content in the molten alloy.The composite obtained by molten infiltration of the alloy with higher Cu content had higher bending strength and fracture toughness,and the values could reach 311.42±24.45 MPa and 14.36±1.42 MPa·m1/2.Friction and wear experiments show that the composite prepared by Ti27Cu73 alloy has the best comprehensive wear resistance,and the specific wear rates after testing with Al2O3,SiC and 440 C steel balls are 13.2466×10-8,9.7359×10-8 and 8.5460×108 mm3·N-1 m-1,respectively.Finally,the reaction activity of Si-Cu alloy with high Cu content and porous C/C preform is weak,the wettability between the alloy and the porous C/C preform is poor,and the infiltration process is difficult to achieve.C/C-SiC-TiC-Cu composite were prepared by adding a small amount of Ti to Si-Cu alloy to improve the wettability of the alloy and the porous C/C preform.It is proved that the addition of Ti effectively improves the wettability between the alloy and the porous C/C preform.The phase composition of C/C-SiC-TiC-Cu composite is C,SiC,TiC,TiSi2,Cu3Si and Si.The analysis of the infiltration mechanism of the composite shows that the ratio of SiC and TiC In the composite can be controlled by adjusting the content of Si in the infiltration alloy.When the atomic ratio of Si in the infiltration alloy is higher than 54%,the SiC reaction layer dominates,and when the atomic ratio of Si is lower than 54%,the TiC reaction layer dominates.