Austenitic stainless steel
Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering
Surface and Interface Analysis,; Vol. 46(2014)p. 856-860
Surface Engineering,; Vol. 33(2017)p. 319-326
Surface and Coatings Technology,; (2017)p. 141-151
European Conference on Heat Treatment 2015 and 22nd IFHTSE Congress - Heat Treatment and Surface Engineering from Tradition to Innovation,; (2015)
Paper in proceedings
Every day, we are surrounded by materials made of austenitic stainless steels. Kitchenware, utensils, food containers, jewelry… just to name a few applications that we cannot imagine our daily life without. Austenitic stainless steels are also necessary for industries, such as chemical, biomedical, pharmaceutical and petrochemical. One of the most attractive features of austenitic stainless steels is high corrosion resistance, especially important in acidic and marine environments. The chromium present within the metal, which gives rise to a chemically and mechanically stable chromium-oxide layer when exposed to oxygen, protects the material from corrosion. Additionally, nickel is added to give the material an “austenitic” structure, further improving the corrosion resistance and enhancing the formability. Unfortunately, one of the most significant drawbacks of austenitic stainless steels is the inherently low hardness. Moreover, austenitic stainless steels cannot be heat-treated like conventional steels, which limits their applicability to non-load bearing applications, otherwise high wear and mechanical failures may occur.
Conventional steels can be treated with nitrogen or carbon at high-temperatures to increase hardness. Unfortunately, this is not a viable option for austenitic stainless steels. High-temperature nitriding/carburizing causes the formation of chromium-compounds, which drastically decreases the corrosion resistance. In contrast, low-temperature treatments, that introduce nitrogen or carbon in the austenitic crystal structure without removing chromium from the steel, can be used. The austenitic structure expands, creating a hard but still corrosion resistant layer.
In this thesis, both plasma- and gas-based carburizing/nitriding techniques were used to form expanded austenite layers on different austenitic stainless steels. The influence of alloying elements on the microstructure and properties of the expanded austenite structure was investigated. The microstructural characteristics, such as thickness and phase constituents, as well as hardness, thermal stability and corrosion resistance were studied by a variety of microscopic and spectroscopic analysis techniques.
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4360
Chalmers University of Technology
Virtual Development Laboratory, Hörsalsvägen 7A, Chalmers
Opponent: Thierry Czerwiec, Université de Lorraine, Nancy, France