| 摘要 |
A process and apparatus for case hardening of ferrous metal work pieces is described in which the work pieces to be processed are placed inside a metal vacuum chamber which is evacuated with a mechanical pump and then backfilled with a partial pressure of a 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, the positive terminal being connected to the chamber wall and to ground. The power supply is energized and some of the gas is converted to ions. The work pieces are heated to temperatures of approximately 650 DEG to 1100 DEG F for ionitriding or to temperatures of approximately 1650 DEG to 1900 DEG for ion carburizing. The heating is effected at least in part by the ion activity. Auxiliary heating by auxiliary heating units built into the chamber may be effected to reduce the time required to bring the work pieces to the reaction temperature. A nitrided and/or carburized case is formed on the work pieces, the case depth being determined by the material of the work pieces, the time, the temperature, the gas or gases introduced and the reaction pressure. Cooling and/or quenching may be effected by a recirculating gas cooling system associated with the vacuum chamber.
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