Abstract: Disclosed are a mold, apparatus and method for obtaining articles of controlled crystallographic orientation using solidification from seeds. The starter section of a directional solidification mold is adapted to both contain a seed and receive molten metal which is flowed over and about a seed to heat and partially melt it. A selector section of the mold has reduced cross section compared to the starter section so that only epitaxially solidified metal will be formed in the article section. A barrier layer resistive to molten metal is applied to portions of the seed to facilitate its removal and reuse.

Abstract: A seed and method for epitaxial solidification of materials, a preferred seed having at least a portion with a melting point 20.degree.-45.degree. C. depressed from that of the alloy being solidified into an article. Boron and silicon are preferably added to nickel superalloys seeds when directionally solidified columnar grain and single crystal articles are formed. Improved seeds also have surface compositions which promote the dissolution of surface contamination films that interfere with epitaxy.

Abstract: 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 mils and an outer layer composed predominantly of zircon having a thickness of from 0.1 to 0.4 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 known as chain porosity. The zircon component of the shell mold had desirable mechanical properties and may 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.

Abstract: In the manufacture of cast articles such as gas turbine blades and vanes from high temperature alloys or eutectics, the heating of the mold in readiness for pouring and the cooling of the mold after pouring are precisely controlled by mechanism responsive to thermocouples internal and external to the mold and moving with the mold and a thermocouple in fixed relation within the furnace. The mechanism is especially adapted for use with the withdrawal technique in which the mold when poured is withdrawn from within the heating furnace past a radiation baffle thereby maintaining a steep thermal gradient within the mold and moving relative to the mold to establish the rate of upward movement of the solidification front within the alloy.