Influence of carburising on distortion behaviour

✍ Scribed by C. Bahnsen; B. Clausen; F. Hoffmann; H.-W. Zoch

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 210 KB
• Volume: 37
• Category: Article
• ISSN: 0933-5137
• DOI: 10.1002/mawe.200500950

✦ Synopsis

Case hardening is a common process to produce steel components, which are characterised by a hard surface combined with a ductile core. As a result of this treatment the parts show a good wear resistance as well as an increase in fatigue strength. High strengthened gear wheels can be mentioned as important examples, being treated in this manner.

The case hardening process consists of a carburising and a hardening treatment. The carbon gradient in the surface results in a gradient in the transformation behaviour. The transformation to ferrite, pearlite and bainite is affected as well as the martensite transformation. Distortion due to these chemical inhomogeneities is added to distortion caused by temperature gradients and temperature gradient implied transformation stresses. In this project the effect of the carburising process on distortion behaviour is investigated. The influence of the microstructure before carburising, the carburising depth, the surface carbon content, the course of the process, the carburising temperature, the hardening temperature and the interaction between these parameters are investigated. Design of experiment methods are used to receive the effect of interactions between the varied parameters and to reduce the number of experiments. Additional investigations concern parameters, which can not be varied completely with the other parameters. The influence of low pressure carburising treatments and carburising at high temperatures, for example, are analysed in a spot-check. The aim of the investigations is to find the decisive parameters affecting distortion in the carburising process, which are later on varied in a design of experiments plan containing the whole production line.