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An investigation into the effect of stress on the formation and stability of carbon s-phase on austenitic stainless steel

Li, Wei (2011)
Ph.D. thesis, University of Birmingham.

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S-phase can be created in austenitic stainless steels by low-temperature thermochemical treatments, which greatly enhanced their hardness, wear resistance and fatigue properties because of the supersaturation by interstitials. One of the technological challenges associated with S-phase surface engineering is that the maximum layer thickness of the S-phase layers is very thin. The thickness of S-phase is restricted by its metastability and precipitation will occur as a result of prolonged treatment.

In this project, the effect of in situ tensile stress on the formation of carbon S-phase on 316L austenitic stainless steel was investigated and it was demonstrated that the tensile stress thickened the S-phase layer by promoting the carbon diffusion in austenitic substrate. However, metastable carbides precipitated when applied tensile stress exceeded 40MPa.

The thermo-mechanical stability of carbon S-phase was studied by creeping (tensile stress) and HIPping (compressive stress) tests. The results showed that the compressive stress retard the decomposition of S-phase by impeding the carbon diffusion; on the other hand, tensile stress promoted the carbon diffusion.

The residual compressive and shear stresses in carbon S-phase was measured be 2.2 GPa and 132 MPa. The wear behaviour of carbon S-phase was studied by dry and oil lubricated reciprocating wear.

Type of Work:Ph.D. thesis.
Supervisor(s):Dong, Hanshan
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Additional Information:

Research from this thesis is published as
Wei Li, Xiaoying Li, Hanshan Dong,
Effect of tensile stress on the formation of S-phase during low-temperature plasma carburizing of 316L foil
Acta Materialia, Volume 59, Issue 14, August 2011, Pages 5765-5774, ISSN 1359-6454,
DOI: 10.1016/j.actamat.2011.05.053.

Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:2894
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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