High Nitrogen Steels: Structure, Properties, Manufacture, Applications

385 Pages·1999·13.381 MB·English

by  Prof. Dr. Valentin G. Gavriljuk, Prof. Dr.-Ing. Hans Berns (auth.)

Engineering Materials
Springer-Verlag Berlin Heidelberg GmbH
Valentin G. Gavriljuk . Hans Berns
High Nitrogen Steels
Structure, Properties, Manufacture, Applications
With 199 Figures
, Springer
Prof. Dr. Valentin G. Gavriljuk
Institute of Metal Physics
36 Vernadsky Prospect
252142 Kiev
Ukraine
Prof. Dr. -Ing. Hans Berns
Lehrstuhl Werkstofftechnik
Ruhr Universität
44780 Bochum
Germany
Cataloging-in-Publication Data applied for
Die Deutsche Bibliothek -CIP-Einheitsaufnahme
Gavriljuk, Valentin G.:
High nitrogen steel: structure, properties, manufacture, applications
Valentin G. Gavriljuk; Hans Berns.
Berlin; Heidelberg; NewYork; Barcelona; Hong Kong; London; Milan;
Paris; Singapur; Tokyo: Springer, 1999
(Engineering materials)
ISBN 978-3-642-08567-3 ISBN 978-3-662-03760-7 (eBook)
DOI 10.1007/978-3-662-03760-7
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© Springer-Verlag Berlin Heidelberg 1999
Originally published by Springer-Verlag Berlin Heidelberg in New York 1999.
Softcover reprint of the hardcover 1s t edition 1999
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Preface
During the second half of this century the nitrogen concentration of steel moved in
both directions: down in constructional grades by oxygen blowing to prevent
brittle fracture upon age hardening at ambient temperature and up in stainless
grades to improve strength, corrosion resistance and austenite stability. The
gradual recognition of the beneficial effects of this element on the properties of
high alloy steels led to a widespread development of high nitrogen steels (HNS)
documented by numerous applications and the proceedings of five HNS
conferences at LilIe (France) 1988, Aachen (Germany) 1990, Kiev (Ukraine)
1993, Kyoto (Japan) 1996 and HelsinkilStockholm (FinnlandISweden) 1998.
The word "high" in HNS is not clearly defined but accounts e.g. for 0.1 mass%
of nitrogen in creep resistant steels, 0.9 mass% in stainless grades or 2 mass% in
tool steels. "High" best refers to "intentionally raised" by appropriate alloying or
by pressure and powder metallurgy. For convenience steel grades are designated
by their approximate content of alloying elements in mass% omitting
unintentional minor additons of Si, Mn, C, P, S asf. As an example
Cr22Ni5M03NO.2 stands for a stainless duplex grade.
The present book starts by comparing the effects of nitrogen and carbon on the
atomic structure and interaction within the crystallattice. Next the constitution of
HNS is investigated leading to specific microstructural features. Based on this
background the mechanisms behind the mechanical, chemical and tribological
properties of HNS are derived. This concludes the fundamentals treated in
chapters one to three. Chapter four comes down to shop practice of manufacturing
HNS which, in respect to e.g. melting, hot working, and welding, may be quite
different from respective carbon grades. In chapter five, different HNS for special
applications are presented like e.g. hardenable steels for stainless bearings, high
strength austenitic steels for non-magnetic retaining rings, superaustenitic stainless
sheet for the chemical industry or solution nitrided impellers for pumps. Chapter
six is an attempt to summarize key aspects of HNS.
The book is meant for material scientist working in the field of high alloy steels
and also for engineers engaged in materials technology, material selection and
design. The work covers a wide scope from the atomic structure to the application
of HNS and was written by a metal physicist and an engineer.
The authors would like to express their gratitude for the assistance of numerous
persons in the institutes at Kiev and Bochum who carried out research on HNS or
helped to prepare this book for print. Thanks are especially extended to Dr. Bela
Shanina, Dr. Alexander Tarasenko, Dipl.-Ing. Andreas Packeisen and Dipl.-Ing.
Martin Schellewald for the layout of the manuscript and figures. The authors also
acknowledge the financial support of their research by the National Academy of
VIII Preface
Science and the Science and Technology Center in Ukraine, by the Federal
Ministry of Research and Education and the Research Foundation of Germany, by
the State of Northrhine-Westphalia and by the European Union.
V.G. Gavriljuk
H. Berns
Contents
1 Structure ............................................................................................................... 1
1.1 State of nitrogen atoms in austenite .......................................................... 2
1.1.1 Electronic structure ............................................................................ 3
1.1.1.1 Interatomic electron exchange .................................................... 7
1.1.1.2 Experimental studies of electronic structure ............................. 10
1.1.2 Distribution ofnitrogen and carbon atoms ...................................... 14
1.1.2.1 Thermodynamical characteristics of solid solutions ................. 14
1.1.2.2 Thermodynamical models of Fe-C(N) austenite ....................... 20
1.1.2.3 Monte Carlo method for thermodynamical simulation of solid
solutions ................................................................................... 24
1.1.2.4 C-C interaction and atomic configurations of carbon in
Fe-C austenite ........................................................................... 26
1.1.2.5 N-N interaction and atomic configurations of nitrogen in
Fe-N austenite ........................................................................... 29
1.1.2.6 Correlation between atomic interaction and short range
atomic order .............................................................................. 33
1.1.3 Interaction of nitrogen atoms with substitutional solutes ................ 42
1.1.3.1 Estimation of interaction energies s-i ....................................... 43
1.1. 3.2 Crystalline symmetry of s-i defects .......................................... 45
1.1.4 Interaction of nitrogen atoms with crystallattice imperfections ...... 49
1.1.4.1 Vacancies .................................................................................. 50
1.1.4.2 Dislocations .............................................................................. 51
1.1.4.3 Grain boundaries ...................................................................... 56
1.1.5 Dislocations and twins in nitrogen austenite ................................... 58
1.1.5.1 Stacking fault energy ................................................................ 58
1.1.5.2 Dislocation structure and twins ................................................ 62
1.2 Distribution of nitrogen atoms in martensite .......................................... 65
1.2.1 Freshly formed Fe-N martensite ...................................................... 66
1.2.2 Early stages of ageing and tempering of nitrogen martensite .......... 71
2 Constitution ................................................................................................... 77
2.1. Thermodynamics of multicomponent solutions ..................................... 77
2.1.1 Solubility of nitrogen in liquid iron and steel.. ................................ 79
2.1.1.1 Effect of alloying elements ....................................................... 80
2.1.1.2 Effect of temperature ................................................................ 82
2.1.1.3 Effect of pressure ...................................................................... 83
X Contents
2.2 Binary Fe-N diagramme ......................................................................... 84
2.3 Multicomponent phase diagrams ............................................................ 91
2.3.1 The calculation ofphase diagrams .................................................. 91
2.3.2 The Fe-Cr-Ni-N phase diagram ....................................................... 93
2.3.3 The Fe-Cr-Mn-N phase diagram ................................................... 100
2.4 Precipitates in austenitic steels ............................................................. 102
2.4.1 Intermetallic phases ....................................................................... 102
2.4.2 Carbides ......................................................................................... 108
2.4.3 Effect of nitrogen on precipitation ................................................. 109
2.4.4 Electron concept for stability of austenitic steels .......................... 116
2.5 Precipitates in martensitic steels ........................................................... 119
3 Key properties ............................................................................................. 135
3.1 Mechanical properties .......................................................................... 135
3.1.1 Solid solution strengthening .......................................................... 136
3.1.1.1 Athermal strengthening .......................................................... 137
3.1.1.2 Temperature dependence of the yield strength ....................... 143
3.1.2 Strengthening by grain boundaries ................................................ 153
3.1.3 Cold work strengthening ............................................................... 159
3.1.4 Toughness ...................................................................................... 169
3.1.5 Fatigue ........................................................................................... 173
3.1.5.1 Austenitic steels ...................................................................... 173
3.1.5.2 Martensitic and duplex steels ................................................. 179
3.1.6 Creep ............................................................................................. 180
3.1.7 Wear .............................................................................................. 183
3.2 Chemical properties .............................................................................. 185
3.2.1 General corrosion .......................................................................... 186
3.2.2 Localised corrosion ....................................................................... 188
3.2.2.1 Intercrystalline corrosion ........................................................ 188
3.2.2.2 Pitting ..................................................................................... 190
3.2.2.3 Crevice corrosion ................................................................... 194
3.2.2.4 Stress corrosion cracking ........................................................ 195
3.2.3 Hydrogen embrittlement.. .............................................................. 198
4 Manufacturing ............................................................................................. 203
4.1 Uptake of nitrogen ................................................................................ 203
4.1.1 Alloying ......................................................................................... 205
4.1.2 Pressure metallurgy ....................................................................... 206
4.1.3 Powder metallurgy ......................................................................... 213
4.1.4 Solution nitriding ........................................................................... 215
4.2 Hot working .......................................................................................... 218
4.2.1 Process ........................................................................................... 219
4.2.2 Microstructure ............................................................................... 220
4.2.3 Surface effects ............................................................................... 221
Contents XI
4.3 Welding ................................................................................................ 223
4.3.1 Pressure welding ............................................................................ 223
4.3.2 Fusion welding .............................................................................. 224
4.4 Heat treatment ...................................................................................... 226
4.4.1 Holding at high temperature .......................................................... 227
4.4.2 Cooling .......................................................................................... 229
4.5 Machining ............................................................................................. 229
4.5.1 Experimental conditions ................................................................ 229
4.5.2 Results ........................................................................................... 230
4.6 Products ................................................................................................ 232
5 Steels and applications ................................................................................ 235
5.1 Martensitic steels .................................................................................. 236
5.1.1 Hard stainless steels ....................................................................... 238
5.1.2 Wear resistant stainless steels ........................................................ 242
5.1.3 High-speed steels ........................................................................... 245
5.1.4 Nickel -martensitic stainless steels ............................................... 248
5.1.5 Stainless quench-and-temper steels ............................................... 250
5.1.6 Steels for inlet valves ..................................................................... 253
5.1.7 Hot work tool steels ....................................................................... 255
5.1.8 Creep resistant low-alloy steel... .................................................... 257
5.1.9 Creep resistant high alloy steels .................................................... 259
5.2 Austenitic steels .................................................................................... 263
5.2.1 Standard stainless steels ................................................................. 265
5.2.2 Low cost stainless steels ................................................................ 267
5.2.3 High strength stainless steels ......................................................... 271
5.2.4 Body friendly steels ....................................................................... 275
5.2.5 Steels of high corrosion resistance ................................................. 276
5.2.6 Cryogenic non-magnetic steels ...................................................... 280
5.2.7 Steels for exhaust valves ................................................................ 284
5.2.8 Creep resistant steels ..................................................................... 286
5.2.9 High temperature nickel alloys ...................................................... 289
5.3 Steels of mixed microstructure ............................................................. 291
5.3.1 Stainless ferritic-martensitic dual-phase steels .............................. 292
5.3.2 Stainless austenitic-martensitic steels ............................................ 294
5.3.3 Stainless ferritic-austenitic duplex steels ....................................... 302
5.4 Steels for solution nitriding .................................................................. 307
5.4.1 Martensitic case ............................................................................. 308
5.4.2 Austenitic case ............................................................................... 313
5.4.3 AppIication of solution nitriding ................................................... 316