Recently Patented Gaseous Carburising and Nitriding Techniques for Stainless Steels and a Review of Other Surface Enhancing Techniques

This article gives an overview of several new, patented (proprietary) carburising and nitriding techniques. The SAT12 process, developed by Swagelok Company, and the Kolsterising process are carburising methods that may give rise to colossal carbon supersaturation to the surface layer of austenitic stainless steels, resulting in substantial improvement to mechanical and corrosion properties. A newly-invented, patented nitriding technique for achieving colossal nitrogen content in the surface layer of austenitic stainless steel is introduced in this article, too. One of the weaknesses of conventional carburization/nitriding techniques is the formation of carbides and nitrides. However, nearly no carbide/nitride/carbonitride precipitation takes place for the new carburising/nitriding techniques until very high C/N contents. Besides, very thick carburized/nitrided layers may be achieved with the new techniques. In addition to carburising and nitriding, a variety of novel, new, and potentially patentable surface enhancing methods (e.g., surface nanostructuring processes and laser surface treatment) are also presented in this article.