Work support for vacuum electric furnaces

Abstract

A work support for vacuum electric furnaces is provided for furnaces in which work pieces to be processed are placed inside a vacuum electric furnace chamber which is evacuated with a mechanical pump and then backfilled with a partial pressure of gas containing nitrogen, such as nitrogen or ammonia, or a hydrocarbon such as methane, or mixtures thereof. The work pieces to be processed are electrically connected to the negative (cathode) terminal of a D.C. power supply, and insulated from the chamber wall which is connected to positive terminal of the D.C. power supply and to ground for safety. The power supply is energized and a portion of the gas is ionized. The work pieces are heated to temperatures of approximately 650.degree. to 1100.degree. F. for ion-nitriding or to temperatures of approximately 1650.degree. to 1900.degree. F. for ion carburizing. The heating is effected at least in part by the ion activity but auxiliary heating elements may be used if desired. Materials that are sputtered from the work travel in straight lines and tend to build up on work supports and cause electrical shorting. Shorting is greatly reduced in this structure by use of shields which comprise insulating discs and spacers supported from the bottom of the furnace.

Dependencies are inferred from the claim text.