Surface Engineering by Expanded Austenite
Aims
Project Descriptor
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.
Objectives
Objective 1 –
Surface Engineering Research
Review the process, history and techniques of carburising as well as the formation and characteristics of an S-Phase
Objective 2 –
Material Properties
Literature search of compositions and typical uses of samples and research into the alloys and the properties of the austenitic structure found in both stainless steels & nickels
Objective 5 –
Investigations
Carry out testing via:
- XRD
- RST
- Optical Microscopy
- XPS
- SEM
- Micro-Hardness Testing
To investigate the effect of the carburisation process
Objective 6 –
Analysis
To analyse the results of the carburisation processes and compare the microstructure of the expanded austenite layer to that of the untreated samples. Further material property characteristics should also be commented on
Objective 3 –
Analysis Techniques
To understand each investigative technique used and how to interpret and analyse the corresponding results
Objective 7 –
Documentation
To continuously work on and update both the papers and website that are required throughout the duration of the project
Objective 4 –
Sample Preparation
Correctly and thoroughly prepare all samples as necessary, following the typical procedure:
- sectioning
- mounting
- grinding
- polishing
- etching
Objective 8 –
Team Reflection
To always work as a partnership to allow for the development of an equal understanding of the project. To optimise the efficiency of the documentation process and ensure that each team member work towards their strengths, whilst bearing in mind their weaknesses