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Permanent link (DOI): https://doi.org/10.7939/R3191N

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Characterization and Evaluation of Aged 20Cr32Ni1Nb Stainless Steels Open Access

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Other title
Subject/Keyword
Thermodynamics
Chemistry
Steel
Stainless
Casting
Optimization
Furnace
Alloy
Liquation
ThermoCalc
Reformer
Characterization
Microscopy
Materials
Embrittlement
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Dewar, Matthew P
Supervisor and department
Mendez, Patricio (Chemical and Materials Engineering)
Gerlich, Adrian (Chemical and Materials Engineering)
Examining committee member and department
Mendez, Patricio (Chemical and Materials Engineering)
Gerlich, Adrian (Chemical and Materials Engineering)
Dubljevic, Stevan (Chemical and Materials Engineering)
Doucette, John (Mechanical Engineering)
Department
Specialization
Materials Engineering
Date accepted
2013-01-28T11:00:03Z
Graduation date
2013-06
Degree
Master of Science
Degree level
Master's
Abstract
20Cr-32Ni-1Nb stainless steel alloys are commonly used in hydrogen reformer manifolds for transporting hot hydrogen by-products at 750-950 celcius. After long periods of exposure, embrittling secondary carbides and intermetallic phases can precipitate at the grain boundaries which can drastically reduce the ductility, and the repair weldability of the alloy. The intermetallic silicide, G-phase, is commonly observed in 20Cr-32Ni-1Nb stainless steels, and is prone to liquation cracking during welding operations. G-phase is deleterious to the material, where a high degree of G-phase coarsening will render the material unweldable. The present work will investigate various methods in mitigating G-phase precipitation. Variations in casting methods, wall thickness, homogenization treatments, and alloy chemistry will be examined by evaluating their microstructure after periodically aging the samples. Thermodynamic equilibrium modeling using computational thermodynamic tools will be used to optimize the 20Cr-32Ni-1Nb chemistry following ASTM specifications.
Language
English
DOI
doi:10.7939/R3191N
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Energy, Materials, fabrication. and repair considerations for hydrogen reformer furnace outlet pigtails and manifolds, Technical Report, API, 2011.H. Baker, H. Okamoto, ASM handbook, volume 03 - Alloy Phase Diagrams, 1992.M. Hillert, Phase Equilibria, Phase Diagrams and Phase Transformations: Their Thermodynamic Basis, Cambridge University Press, 2007.S. G. F. Hans Lukas, B. Sundman, Computational Thermodynamics, Cambridge University Press, 2007.Dewar, M. and A. Gerlich, Correlation Between Experimental and Calculated Phase Fractions in Aged 20Cr32Ni1Nb Austenitic Stainless Steels Containing Nitrogen. Metallurgical and Materials Transactions A, 2012: p. 1-13.

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File title: 1 Introduction
File title: Characterization and Evaluation of Aged 20Cr32Ni1Nb Stainless Steels
File author: Matt Dewar mpdewar@ualberta.ca
Page count: 235
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