Electromagnetic soft-contact confinement and directional solidification of near-net shape castings of superalloys

The properties of turbine blade castings made of superalloys are often dissatisfactory because the melts of superalloys are contaminated by the ceramic mold materials. By electromagnetic soft-contact confinement process, the melts of superalloys are half-suspended by electromagnetic pressure, which decreases the contacting area and time between the melts and the magnetic mold material. Simultaneously, the purification of liquid metals is improved. The combination of electromagnetic soft-contact confinement process and directional solidification process, the new technique for manufacturing near-net shape castings of superalloys is proposed, and the effect of ceramic, magnetic mold and graphite materials on the magnetic flux density distribution in the coil is investigated. It is shown that the height of graphite not only affects the magnetic flux density, but also the temperature field distribution in the melts. By selecting suitable technological parameters, such as the upper and lower coil powers, and pulling rate etc., two near net shape turbine blade castings with directionally solidified microstructure are successfully manufactured by electromagnetic soft-contact confinement process.