The Study On The Microstructure And The Properties Of The 3D-Meshy SiC/2Cr13 Composite Material

With the improvement of aerospace, a new type of braking material which has high hardness, good wear resistance and good friction and wear properties-the 3D-Meshy silicon carbide ceramic/metal composite has attracted people's attention. Silicon carbide ceramic and metal can support skeleton for each other in this material, so that it can possesses metal excellent properties such as high toughness,high intensity as well as silicon carbide ceramic outstanding properties such as high hardness,good wear resistance and good heat-resistance. These advantages make this material have excellent friction and wear behavior. The interface reactions between reinforcement and matrix have strongly affected physical and mechanical properties of this material. Therefore, the study on the interfacial reactions between silicon carbide skeletons and 2Cr13 matrix has extremely important meaning.In this paper, microstructure and formation mechanism of the matrix and the interface of SiC/20Cr composite materials have been studied, as well as the friction and wear behavior, ordinary mechanical properties. The results show that:(1) The microstructure of the matrix is ball pearlite. There is good interfacial adhesion between 3D-Meshy SiC and metal. The reaction zone included two zones:silicon carbide reaction zone(SRZ) and metal reaction zone(MRZ), and the MRZ can be divided two zones: poor chromium zone(PCZ-MRZ) and rich chromium zone(RCZ-MRZ). SRZ which is near silicon carbide is mainly composed of Fe5Si3,Cr5Si3,Cr3Si,Cr7C3 and Cr23C6,etal; RCZ-MRZ which is near 2Cr13 mainly contains Cr23C6; PCZ-MRZ which is between SRZ and RCZ-MRZ is mostly made up of iron-rich phrase Fe2Si.(2) In the reaction zone of SiC/2Cr13 interface, the order of the interface formation is determined by the solidification rate of the material resultant. Cr23C6 in the PCZ-MRZ casts firstly, so that PCZ-MRZ generates first of all; Secondly, Fe2Si casts in the RCZ-MRZ, part of Fe2Si has no time to deform and preserves in the fast cooling; Finally, Fe5Si3 which deformed by Fe2Si casts in the SRZ. In the process of cooling, the solid-solution chromium,carbon and silicon atoms precipitates in the form of compound. The reactions between C, Si atoms decompose by SiC with the iron and chromium atoms of the metal have selectivity. The affinity of Cr-C is obviously higher than Fe-C, and the affinity of Cr-C is almost identical to Cr-Si. Therefore, in the momentary liquid reaction, Fe5Si3,Cr5Si3,Cr7C3,Cr23C6 and Cr3Si precipitate in the interface. Reaction taking place in the liquid phrase is the main reaction, but solid-phrase plays a great role on uniform and ordering of interface product.(3) The silicon carbide deforms under the action of irons which diffuses from the matrix after heat-treatment at 800℃, the carbide atoms and the silicon atoms react with the compounds in the SRZ. Meanwhile, the Cr-C and the Cr-Si compounds which solutes in the Fe-Si precipitate and grow. The microstructure seems more uniform and ordering. The diffusion coefficients of the iron atoms and silicon atoms calculated by the experiment are 1.607×10-11m2·s-1 and 4.037×10-12m2·s-1 respectively.(4) The simulated car braking experiment which the 3D-Meshy SiC/2Cr13 is used as the stationary ring and the cast iron which contains nickel and molybdenum is used as the rotating ring is carried out. The results show that:the friction and wear behavior of the composite is excellent at the low and high speed, but when the speed reaches 7000rpm, the friction surface of the stationary ring which suffers bad breakage for the severe adhesion makes the friction performance fall sharply. Abrasive wear is the dominant wear of the stationary ring and the rotating ring at small speed and low pressure, but when the speed rises and the pressure increases, abrasive wear is the dominant wear of the stationary wear, adhesive wear of the rotating ring.(5) The tensile strength of the 3D-Meshy is very low, its sbb is11MPa. The plastic of the composite comes down quickly for the reaction between silicon carbide and 2Cr13, the rupture of the metal presents typical brittle rupture.