METHOD FOR FABRICATION COMPOSITE SHELL MOLDS FOR THE PRODUCTION OF SUPERALLOY CASTINGS

摘要

A method for producing composite ceramic shell molds for investment casting and subsequent directional solidification of nickel and cobalt base superalloys is described. The composite ceramic shell mold is composed of an inner component having an alumina content of at least 80 percent and an average thickness of about ten mills and an outer layer composed predominantly of zircon having a thickness of from .1 to .4 inches. The alumina component of the shell mold is wet by the superalloy material and this wetting action is believed to cause the substantial elimination of a surface defect problem know as chain porosity. The zircon component of the shell mold had desirable mechanical properties and my easily be removed from the solidified casting. The alumina and zircon components are bonded together in such a fashion that they will not separate during the casting process.