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 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifieally the rights of translation, reprinting, reuse of illustrations, recitation, broadeasting, reproduction on microfilm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution act under German Copyright Law. Springer-Verlag Berlin Heidelberg 1999 Originally published by Springer-Verlag Berlin Heidelberg in New York 1999. Softcover reprint of the hardcover 1 st edition 1999 The use of general descriptive names, registered names, trademarks, ete. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Camera-ready eopies from authors Cover-Design: MEDIO, Berlin Printed on acid-free paper SPIN 10730039 6213020 5 4 3 2 1 0
to BELA and ISOLDE
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
XII Contents 6 From structure to development...... 323 6.1 Structure... 323 6.2 Properties... 326 6.3 Technical relevance... 330 References... 335 Index... 373