Fe-C and Fe-N compound layers [Elektronische Ressource] : growth kinetics and microstructure / vorgelegt von Thomas Greßmann

Gressmann

Informations

• Publié par: universitat_stuttgart
• Publié le: 01 janvier 2007
• Nombre de lectures: 17
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Max-Planck-Institut für Metallforschung
Stuttgart

Fe-C and Fe-N compound layers:
Growth kinetics and microstructure

Thomas Greßmann
Dissertation
an der
Universität Stuttgart

Bericht Nr. 206
September 2007

2

Fe-C and Fe-N compound layers:
growth kinetics and microstructure

Von der Fakultät Chemie der Universität Stuttgart zur
Erlangung der Würde eines Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigte Abhandlung


vorgelegt von

Thomas Greßmann

aus Bayreuth


Hauptberichter: Prof. Dr. Ir. E.J. Mittemeijer
Mitberichter: Prof. Dr. F. Aldinger
Mitprüfer: Prof. Dr. H. Bertagnolli

Tag der Einreichung: 05.07.2007
Tag der mündlichen Prüfung: 24.09.2007




INSTITUT FÜR METALLKUNDE DER UNIVERSITÄT STUTTGART
MAX-PLANCK-INSTITUT FÜR METALLFORSCHUNG
STUTTGART, 2007 2
Table of contents
1 Introduction............................................................................................................. 7
1.1 Thermodynamics of gas nitriding and gas nitrocarburising ................................. 9
1.1.1 Nitriding in NH /H gas mixtures................................................................ 10 3 2
1.1.2 Carburising in CO containing gas mixtures................................................. 12
1.1.3 Gas nitrocarburising..................................................................................... 13
1.2 Crystal structure and homogeneity range of γ΄-Fe N , ε-Fe (N,C) and 4 1-y 3 1+x
cementite............................................................................................................. 14
1.3 Growths kinetics of iron-(carbo-)nitride compound layers ................................ 16
1.4 Microstructure of Fe-N compound layers........................................................... 17
References................................................................................................................. 19
2 Formation of massive cementite layers on iron by ferritic carburising in the
additional presence of ammonia .......................................................................... 21
2.1 Introduction......................................................................................................... 22
2.2 Experimental procedure...................................................................................... 23
2.2.1 Specimen preparation and thermochemical treatment................................. 23
2.2.2 Analysis of the (nitro-)carburised specimens .............................................. 24
2.3 Results and discussion ........................................................................................ 26
2.3.1 Influence of the ammonia content in the atmosphere on the layer
constitution .................................................................................................. 26
2.3.2 Cementite layer-growths kinetics ................................................................ 31
2.4 Conclusions......................................................................................................... 33
References................................................................................................................. 35
3 X-ray diffraction line-profile analysis of hexagonal ε-iron-nitride compound
layers: composition- and stress-depth profiles ................................................... 37
3.1 Introduction 38
3.2 Experimental....................................................................................................... 41
3.2.1 Specimen preparation .................................................................................. 41
3.2.2 Metallography.............................................................................................. 43
3.2.3 TEM and EBSD ........................................................................................... 43 4 Contents
3.2.4 X-ray diffractometry .................................................................................... 43
3.3 Theoretical considerations .................................................................................. 45
3.3.1 Model for the microstructure of ε layers...................................................... 45
3.3.1.1 Lattice-parameter-depth profile ............................................................ 45
3.3.1.2 Stress-depth profile............................................................................... 47
3.3.2 Diffraction effects of the microstructure model .......................................... 48
3.3.3 Data-evaluation method 50
3.4 Results and discussion ........................................................................................ 54
3.4.1 Microstructure of the ε layers, as determined by optical microscopy, TEM
and EBSD .................................................................................................... 54
3.4.2 Qualitative description of the diffraction-line profile and preliminary
analysis ........................................................................................................ 55
3.4.3 Results of the fitting and discussion ............................................................ 59
3.4.3.1 Lattice-parameter-depth profiles........................................................... 59
3.4.3.2 Residual stress-depth profiles ............................................................... 64
3.5 Conclusions......................................................................................................... 69
Appendix................................................................................................................... 71
Acknowledgement .................................................................................................... 71
References................................................................................................................. 72
4 Elastic anisotropy of γ΄-Fe N and elastic grain interactions in γ΄-Fe N layers 4 4 1-y
on α-Fe: first-principles calculations and diffraction stress measurements.... 75
4.1 Introduction......................................................................................................... 76
4.2 First-principles calculations of elastic constants ................................................ 79
4.2.1 Theoretical background and method of calculation used ............................ 79
4.2.2 Results.......................................................................................................... 83
4.3 Macrostrains and macrostresses in γ΄-Fe N layers.......................................... 84 4 1-y
4.3.1 Determination of residual macrostresses by diffraction methods ............... 84
4.3.2 Experimental................................................................................................ 88
4.3.2.1 Specimen preparation and metallography ............................................ 88
4.3.2.2 X-ray diffractometry ............................................................................. 89
4.3.3 Results of X-ray stress analysis ................................................................... 90
4
Contents 5
4.4 Discussion........................................................................................................... 94
4.4.1 Interpretation of the calculated single-crystal elastic constants .................. 94
4.4.2 The effective, experimentally determined type of grain interaction............ 98
4.5 Conclusions......................................................................................................... 99
Acknowledgement .................................................................................................. 100
References............................................................................................................... 100
5 Zusammenfassung............................................................................................... 105
5.1 Einleitung.......................................................................................................... 105
5.2 Experimentelles................................................................................................. 107
5.3 Ergebnisse und Diskussion ............................................................................... 108
5.3.1 Bildung und Wachstumskinetik von massiven Zementitschichten ........... 108
5.3.2 Röntgenbeugungsanalyse von ε-Fe N Schichten: Linienprofilanalyse.110 3 1+x
5.3.3 Elastische Anisotropie von γ΄-Eisennitrid ................................................. 112
Literatur................................................................................................................... 114
List of publications.................................................................................................... 115
Danksagung ............................................................................................................... 117
Curriculum Vitae...................................................................................................... 119

5
6 Contents
6



1
Introduction


Thermoc