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Oxidation behaviour of Austenitic stainless steels at high temperature in supercritical plant

Simms, Henry George (2011)
M.Res. thesis, University of Birmingham.

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Abstract

Fossil power plant efficiency is improved by increasing steam temperature and pressure. Current martensitic and ferritic steels do not have the required oxidation and spallation properties for boiler tube applications as service conditions increase. Spallation inside the tube can lead to blockage, overheating, creep rupture and turbine erosion. The current steels are limited to 620oC, therefore austenitic stainless steels are proposed for boiler tube applications to enable higher operating conditions. This investigation compared the oxidation and spallation behaviour of the current martensitic steels (T91, T92) with the proposed austenitic stainless steels (super 304H, shot peened super 304H, 347HFG), in air at 600-700oC. Oxide morphology was characterised using SEM and EDX analysis and oxidation kinetics were recorded using specific mass gain and oxide thickness measurements over time. The martensitic steels formed non-protective Fe-rich oxides, which consistently spalled on cooling. The austenitic stainless steels showed little spallation and less mass gain compared to the T92 steel. Double-layered oxides formed on the super 304H and 347H FG steels consisting of an inner protective Cr-rich spinel oxide and an outer Fe-rich oxide. Shot peening increased the oxidation resistance of the super 304H steel forming significantly thinner, single-layer Cr-rich oxides with less mass gain.

Type of Work:M.Res. thesis.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials Engineering
Subjects:TJ Mechanical engineering and machinery
TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:1689
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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