S. Shendye, Metal Casting Technology, Inc., Milford, NH; D. Cargill, Hitchiner Manufacturing Co., Inc., Milford, NH
The Counter-gravity Positive-pressure Vacuum (CPV) casting process is an investment casting process developed and patented by Hitchiner Manufacturing Company, Inc. This process is used to cast high quality components in reactive metals such as Ni and Co-based superalloys. During the CPV process, a hard vacuum is created in the mold and melting chambers. An impermeable fill pipe protrudes from the bottom of the mold chamber and is sealed to the mold. The mold chamber is then moved so that the fill pipe is inserted into the liquid bath which is induction heated and contained in the melt chamber. Pressure is then applied to the melt chamber, thus forcing the metal upward through the fill pipe and into the mold. Typically, pressure is applied on top of the melt surface using an inert gas such as argon. Pressure control over the melt surface results in a controlled rate of filling of the mold which enables casting of extremely thin walled polycrystalline components with walls as thin as 0.015 inch. Chemical composition, NDTE x-ray and fluorescent penetrant inspection (FPI) requirements, mechanical properties, and microstructure specifications are routinely met and exceeded for all the alloys cast. A large number of superalloy components are currently produced using the CPV process by Hitchiner at their manufacturing facility in Milford, NH. Some of these applications along with properties and microstructures, and the specific advantages of the CPV process will be reviewed.
Summary: This paper will describe an innovative process for vacuum melting and investment casting of highly reactive Ni and Co-base superalloys. This process is currently in production and several examples of components cast will be discussed.