The project entitled ‘Surface Engineering on Austenitic Stainless Steel by Expanded Austenite’ has been developed as a sub-topic of the PhD work being carried out by Giulio Maistro at Chalmers University of Technology, Gothenburg; who is investigating ‘Surface Engineering on Austenitic Stainless Steel by Nitrogen Stabilised Expanded Austenite.’

 

The project is based upon subjecting austenitic alloys of different compositions, surface finishes and surface roughness’s to a low temperature (~550°C) carburising process in order to case harden the material, whilst maintaining the corrosion resistant, passive surface layer. The diffusion of the carbon atoms within the crystal lattice of the alloy creates a phase known as expanded austenite (S-phase). The aim of the project is to investigate the microstructure, phase constituents and mechanical properties of the modified layer due to the expanded austenite, as well as to compare the samples post and prior to carburising.

 

A total of nine commercial stainless steels and nickel based alloys with systematically varied chromium, nickel and molybdenum concentrations were selected to be subjected to an industrial carburising process. The exact details of the carburisation process are not available as it is a patented technology. In addition, the nickel based alloys were duplicated and were treated with two different carburising processes to allow for additional analytical comparisons, as nickel based alloys are more resistive to carburisation.