Aspects microstructuraux de l'oxydation d'alliages de Zirconium, Microstructural aspects of the oxidation of zirconium alloys

Christian Proff

Description

Sous la direction de Clement Lemaignan
Thèse soutenue le 06 mai 2011: Grenoble
Cette thèse est axée sur la caractérisation microstructurale des précipités dans les oxydes des alliages binaires de zirconium (1 wt.% Fe, Cr , Ni ou 0.6 wt.% Nb). La température d'oxydation est fixée au 415°C. Les échantillons sont oxydés dans l'air et dans l'autoclave sous des pressions différentes et dans un microscope électronique à balayages environnemental sous vapeur d'eau. Les résultats des recherches peuvent être résumés ci-dessous : -Deux types d'oxydation (retardée et non retardée) ont été observés pour les précipités. -Le facteur de Pilling-Bedworth des précipités est plus élevé par rapport à celui de zirconium. -Les précipités contenant du fer entrainent une formation des cristaux de l'oxyde de fer pur à la surface du matériau, quand les précipités sont à la surface ou à la proximité. Ces observations mènent à la conclusion que le comportement d'oxydation des précipités peut être corrélé à leurs compositions et à la tendance d'oxydation de leurs éléments constituants.
-Alliages binaires de zirconium
-Précipités
-Corrosion
-Oxyde
-MET
-Microstructure
This thesis is focused on the microstructural characterisation of precipitates in the oxide of binary zirconium alloys (1 wt.% Fe, Cr or Ni or 0.6 wt.% Nb) under different oxidation conditions at 415°C. The samples were oxidised in autoclave in air and steam and in an environmental scanning electron microscope in water vapour. The microstructural evolution of the precipitates during oxidation was characterised using electron microscopy. The findings from the analysis are the following: -Two types of oxidation behaviour are observed for precipitates. -Pilling-Bedworth ratio of precipitates is higher than that of the zirconium matrix. -Formation of pure iron oxide crystals on the surface for iron bearing precipitates close to or at the surface. From these observations it is concluded that the precipitate oxidation behaviour can be correlated to precipitate composition and oxidation tendency of the elements in the precipitates. Iron exhibits clearly different behaviour.
-Binary zirconium alloys
-Precipitates
-Corrosion
-Oxide
-TEM
-Microstructure
Source: http://www.theses.fr/2011GRENI027/document

Sujets

• Oxyde
• Tém

Informations

• Publié par: Thesee
• Nombre de lectures: 59
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

THÈSE
Pour obtenir le grade de
DOCTEUR DE L’UNIVERSITÉ DE GRENOBLE
Spécialité : Matériaux, Mécanique, Génie civil, Electrochimie
Arrêté ministériel : 7 août 2006



Présentée par
Christian PROFF


Thèse dirigée par Clément LEMAIGNAN et
codirigée par Sousan ABOLHASSANI

préparée au sein du Laboratory for Nuclear Materials
Paul-Scherrer-Institut, 5232 Villigen, Suisse

dans l'École Doctorale I-MEP2


Aspects microstructuraux de
l´oxydation d´alliages de
zirconium

Thèse soutenue publiquement le 06.05.2011,
devant le jury composé de :
Dr. Pierre BARBERIS
HDR, CEZUS Ugine, Rapporteur
Prof. Arthur MOTTA
Professeur Penn State University, Rapporteur
Dr. Didier GILBON
Directeur Laboratoire Matériaux, Président
Dr. Sousan ABOLHASSANI
Directeur Zr Laboratoire Matériaux PSI, Membre
Prof. Clément LEMAIGNAN
Professeur, INPG Dir. Recherche CEA, Membre
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Abstract
This thesis is focused on the microstructural characterisation of precipitates in the oxide of
binary zirconium alloys (1 wt.% Fe, Cr or Ni or 0.6 wt.% Nb) under different oxidation
conditions at 415°C. The samples were oxidised in autoclave in air and steam and in an
environmental scanning electron microscope in water vapour.
The microstructural evolution of the precipitates during oxidation was characterised using
electron microscopy.
The findings from the analysis are the following:
 Two types of oxidation behaviour are observed for precipitates.
 Pilling-Bedworth ratio of precipitates is higher than that of the zirconium matrix.
 Formation of pure iron oxide crystals on the surface for iron bearing precipitates
close to or at the surface.
From these observations it is concluded that the precipitate oxidation behaviour can be
correlated to precipitate composition and oxidation tendency of the elements in the
precipitates. Iron exhibits clearly different behaviour.



Keywords: binary zirconium alloys, precipitates, corrosion, oxide, TEM, microstructure


















An electronic version of the thesis can be found on the following server:
http://tel.archives-ouvertes.fr (please give title and author name to find the thesis)
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dedicated to my beloved parents and Sonja
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Acknowledgements

First I would like to thank Dr. M.M. Dadras from CSEM in Neuchâtel, and M. Leboeouf,
who made the in situ oxidation experiments possible and teached me the use of AFM and the
in situ heating stage and were there when I needed help with my experiments. Also thank you
very much for the support and your contribution (in particular that of Dr. V. Spassov) for
performing the bulge tests, which turned out to be more time consuming than expected.
I would like to thank very much the financial contribution from swissnuclear for the
project which was a constant support for this thesis.
It was an honour to work with my supervisor Dr. Sousan Abolhassani, who guided me
through the world of electron microscopy and zirconium alloy corrosion and shared with me
her knowledge in this field. I appreciated the high degree of freedom I enjoyed, allowing me
to perform all the interesting experiments that I wanted to. Her patience with me when things
went not as they should was endless, as well as her support, scientific as personal.
I would like to thank Prof. Clément Lemaignan for accepting to supervise this project,
many stimulating discussions, his external view on the work that helped to see the broader
context and his valuable feedback during the write-up of the thesis.
The contribution from Dr. Pierre Barberis from CEZUS is acknowledged, who provided
the material for this study and accepted to be part of the PhD jury.
Dr. VenkatRao Mallipudi was a great help with his expert ANSYS knowledge,
indispensable for the creation of the macro for evaluating precipitate influence on the stresses
in the oxide scale.
Dr. Manuel Pouchon I would like to thank for all his assistance with nanoindentation.
I am indebted to E. Minikus, who was a great help with minor and major issues concerning
the TEM operation and the sample preparation laboratory. J. Krbanjevic is thanked for the
time she spent teaching me the use of the FIB/SEM and preparing my first TEM specimens.
Thanks also to the other helpful persons in the microscopy lab, who helped to quickly solve
problems. It was a pleasure to work with Röbi, who was always ready to provide assistance to
the autoclave experiments, training of our Master student Bhadri and with computer issues.
The same should be said about other people from the Hotlab, Andrej Bullemer, Agathe
Waelchli and Marcus Keller, who provided support in technical issues.
I would also express my gratitude to my roommates Paul, Sebastiano, Hygreeva,
VenkatRao and Cyprian for the nice atmosphere in our office and the valuable help with all
kinds of problems and my friends from the lunch group, Iza, Per, Cedric, Maria, Dorota,
Christian and Tatjana, for the nice atmosphere and distraction, which was helpful to see things
from a different perspective.
Dr. Johannes Bertsch, Dr. Stephane Valance and Dr. Cedric Cozzo are thanked for their
help with the translation of parts of this thesis into French.
This would not have been possible without the support and love from my family and Sonja,
who had to accept me being distracted by things completely foreign to them.
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Table of content
Abstract.................................................................................................................................. 1
Acknowledgements ............................................................................................................... 4
Table of content...... 5
Abbbreviations ...................................................................................................................... 9
1 Introduction. 11
2 Literature...................................................................................................................... 13
2.1 Development of zirconium alloys for nuclear applications ................................. 13
2.2 Microstructure of zirconium alloys...................................................................... 15
2.2.1 Heat treatment..............................................................................................15
2.2.2 Secondary phase particles ............................................................................ 17
2.3 Oxidation of zirconium and its alloys .................................................................. 19
2.3.1 Testing conditions in water and steam ......................................................... 20
2.3.2 ditions in air............................................................................... 21
2.3.3 Corrosion kinetics........................................................................................21
2.3.4 Matrix oxidation...........................................................................................23
2.3.5 Precipitate oxidation.....................................................................................28
2.4 Zirconium oxide and its properties....................................................................... 31
2.4.1 Mechanical aspects of the oxidation of zirconium alloys ............................ 33
2.4.2 Mechanical properties of zirconia................................................................ 34
2.5 Open questions concerning corrosion of (binary) zirconium alloys .................... 36
3 Materials and methods.................................................................................................37
3.1 Materials...............................................................................................................37
3.1.1 Binary alloys................................................................................................37
3.1.2 Pure zirconium, Zircaloy-2 and Zircaloy-4.................................................. 38
3.1.3 Overview of available samples .................................................................... 38
3.2 Oxidation experiments.........................................................................................39
3.2.1 In situ oxidation campaigns.......................................................................... 39
3.2.2 Autoclave oxidation.....................................................................................41
3.2.3 Furnace