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Title: The effect of post weld heat treatment on the creep behaviour and microstructural evolution in grade 92 steel welds for steam pipe applications
Authors: Xu, X.
West, G.D.
Thomson, Rachel C.
Parker, J.
Editors: Gandy, D.
Shingledecker, J.
Issue Date: 2014
Publisher: © ASM International
Citation: XU, X. ... et al, 2014. The effect of post weld heat treatment on the creep behaviour and microstructural evolution in grade 92 steel welds for steam pipe applications. IN: Gandy, D. and Shingledecker, J. (eds). Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference (EPRI 2013), 22nd-25th October 2013, Waikoloa, Hawaii, USA. ASM International, pp. 615 - 626.
Abstract: Grade 92 steel has been widely applied in the power generation industry for use as steam pipes, headers, tubes, etc. owing to a good combination of creep and corrosion resistance. For the welding of thick section pipes, a multi-pass submerged arc welding process is typically used to achieve sufficient toughness in the weld. To relieve the internal stress in the welds and to stabilise their microstructures, a post weld heat treatment (PWHT) is commonly applied. The heat treatment conditions used for the PWHT have a significant effect on both the resulting microstructure and the creep behaviour of the welds. In this study, interrupted creep tests were carried out on two identical Grade 92 welds that had been given PWHTs at two different temperatures: 732°C and 760°C. It was found that the weld with the lower PWHT temperature had a significantly reduced stain rate during the creep test. In addition, microstructural examination of the welds revealed that the primary location of creep damage was in the heat affected zone in the sample with the lower PWHT temperature, whereas it was in the weld metal in the sample with the higher PWHT temperature. To understand the effect of the different PWHT temperatures on the microstructure, initially the microstructures in the head portions of the two creep test bars were compared. This comparison was performed quantitatively using a range of electron/ion microscopy based techniques. It was apparent that in the sample subjected to the higher PWHT temperature, larger Laves phase particles occurred and increased matrix recovery was observed compared with the sample subjected to the lower PWHT temperature.
Description: Copyright 2014 ASM International, www.asminternational.org. This article was published in Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this article for a fee or for commercial purposes, or modification of the content of this article is prohibited.
Sponsor: The authors would like to thank EPRI for the support of this project.
Version: Accepted for publication
URI: https://dspace.lboro.ac.uk/2134/14297
ISBN: 9781627080606
Appears in Collections:Conference Papers and Presentations (Materials)

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