Experiments Of Densification Of SiC Powers By Magnetic Pulse Compaction And Pressureless Sintering

As one kind of special ceramic material, SiC has many excellent performancewith high strength, high hardness, high temperature resistance, corrosion resistance,abrasion resistance, thermal-shock resistance, which used in aerospace,petrochemical, ceramic armor, and other areas. At present, the preparation processof the high-performance SiC is mainly hot-pressing sintering, but the disadvantagesof the efficiency of production, preparation of complex large parts limits the wideapplication of SiC. Magnetic pulse compaction (MPC) process has been successfullyused in powder metallurgy field as the green body obtained by MPC process hashigh density, good uniformity, and so on. If it is used in ceramic fields successfully,it is potential to reduce the sintering temperature, shorten the sintering time and getthe net-shape sintered body.In this paper, the power compaction analysis model is established by Shimayield criteria and the Power module in MSC.MARC2005. The change process ofrelative density, the stress and the power flow of the SiC is analysised. The unevendistribution of the relative density is due to the friction: where on the wall surface isthe highest relative density area, as well as in the wall surface is the lowest relativedensity area. In order to alleviate the uneven distribution, we improved the frictioncoefficient, punch speed, power quality and other parameters. The follow resultsshow that the uneven distribution phenomenon is relieved.SiC powers are compacted by MPC process with the flat coil. It analysis therelations between green density, microscopic fracture morphology and the binder,the power quality, the capacitance, the discharge energy, discharge times, and so on.Experiments show that the formability is improved as the binder is added, increasingthe discharge energy and the discharge times can increase the green density, but itneeds the right energy parameters. Increasing discharge capacitance can improve thegreen density, the density of green body obtained by MPC process is significantlyhigher than conventional process, about0.23g/cm3or so. The changes of themicroscopic fracture morphology of the green body obtained by MPC process aresimilar with the green density. The microscopic fracture morphology shows that itsparticles are refined which are obtained by MPC process, and also its strength isbetter.Through high temperature pressureless sintering experiments, the weightlessrate, the line shrinkage rate, hardness, fracture toughness, thermal expansioncoefficient and microscopic fracture of the sintered body obtained by MPC processare compared with conventional moulding process. Results show that the performance of sintered body obtained by the conventional moulding is superior toMPC process. These show that the advantages about MPC process are disappearedin current conditions.