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Licensed Unlicensed Requires Authentication Published by De Gruyter June 11, 2013

Low-temperature gaseous surface hardening of stainless steel: the current status

Thomas L. Christiansen and Marcel A. J. Somers


The present review addresses the state of the art of low-temperature gaseous surface engineering of (austenitic) stainless steel and is largely based on the authors' own work in the last 10 years. The main purpose of low temperature gaseous surface engineering of stainless steel is to develop a hardened case at the surface, while maintaining the superior corrosion performance. This can be achieved by dissolving colossal amounts of nitrogen and/or carbon without forming nitrides and/or carbides, thus developing so-called expanded austenite. The present work gives an overview over results obtained on homogeneous expanded austenite and covers the crystallography for nitrogen- and carbon-stabilised expanded austenite, the solubility for nitrogen and carbon, the diffusion of these interstitials as well as the stability of expanded austenite with respect to nitride and carbide formation. Subsequently, the fundamental understanding acquired on homogeneous samples is applied to understand the morphology, composition, and residual stress distribution in functionally graded material, as obtained by nitriding, carburising or nitrocarburising of austenitic stainless steel. Thereafter, aspects of modelling the compositional changes occurring during nitriding are addressed. The overview summarises with an outlook towards future scientific challenges.

* Correspondence address, Prof. Marcel A.J. Somers Department of Mechanical Engineering Technical University of Denmark Kemitorvet b. 204, DK-2800 Kgs. Lyngby, Denmark Tel.: +45 45 252 250 E-mail:


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Received: 2009-6-1
Accepted: 2009-7-25
Published Online: 2013-06-11
Published in Print: 2009-10-01

© 2009, Carl Hanser Verlag, München