Method and use of an apparatus for the thermal treatment, in particular nitriding treatment, of metal workpieces

US6328819A · kind A · utility

Assignee

• Ipsen International, GmbH · US

Inventors

• Wolfgang Lerche · Kleve, DE
• Bernd Edenhofer · Kleve, DE
• Michael Lohrmann · Kleve, DE

Key dates

• Filing date: Apr 28, 2000
• Grant date: Dec 11, 2001
• Expiry date: Apr 28, 2020

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C8/34
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

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: PA1 a) heating the workpieces to a temperature between 400.degree. C. and 500.degree. C. in a gas atmosphere comprising only ammonia; PA1 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; PA1 c) maintaining the workpieces at this temperature and in this gas atmosphere for a period of between 0.1 hour and 5 hours; PA1 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, PA1 e) cooling the workpieces to room temperature.