Method and use of an apparatus for the thermal treatment, in particular nitriding treatment, of metal workpieces
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United States of America Patent
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Dec 11, 2001
Grant Date -
N/A
app pub date -
Apr 28, 2000
filing date -
Feb 4, 2000
priority date (Note) -
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Abstract
A method is provided for heat treatment of metal workpieces obtain a substantially uniform nitride layer, even in workpieces comprising high alloy iron articles. The following method steps are provided: a) heating the workpieces to a temperature between 400.degree. C. and 500.degree. C. in a gas atmosphere comprising only ammonia; b) continuing to heat the workpieces to a temperature between 500.degree. C. and 700.degree. C. in a gas atmosphere containing ammonia and an added oxidizing agent; c) maintaining the workpieces at this temperature and in this gas atmosphere for a period of between 0.1 hour and 5 hours; d) continuing to maintain the workpieces at this temperature for a period of between 1 hour and 100 hours in a gas atmosphere containing ammonia or containing ammonia and a carbon-releasing substance; and, e) cooling the workpieces to room temperature.
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