REFRACTORY METAL ALLOYS Metallurgy and Technology Editors

I. Machlin Materials and Processes Branch Naval Air Systems Command Departrn.ent of the Navy Washington, D.C. R. T. Begley Astronuclear Laboratory Westinghouse Electric Company Pittsburgh, Pennsylvania atnd E. D. Weisert Materials Research Rocketdyne Division North American Rockwell CompOh/,y Canoga Park, California '$i1YOt~~ •A Publication of The Metallurgical Society of AIME

REFRACTORY METAL ALLOYS Metallurgy and Technology

Proceedings of a Symposium on Metallurgy and Tech• nology of Refractory Metals held in Washington, D.C., April 25-26, 1968. Sponsored by the Refractory Metals Committee, Institute of Metals Division, The Metallurgi• cal Society of AIME and the National Aeronautics and Space Administration, Washington, D.C.

<±> PLENUM PRESS • NEW YORK • 1968 ISBN 978-1-4684-9122-7 ISBN 978-1-4684-9120-3 (eBook) 001 10.1007/978-1-4684-9120-3

Plenum Press is a division of Plenum Publishing Corporation 227 West 17 Street, New York, N. Y.10011 Preface

This publication documents Proceedings of the Symposium on Metal• lurgy and Technology of Refractory Metal Alloys, held in Washington, D.C. at the Washington Hilton Hotel on April 25-26, 1968, under sponsorship of the Refractory Metals Committee, Institute of Metals Division, of the Metallurgical Society of AIME, and the National Aeronautics and Space Administration. The Symposium presented critical reviews of selected topics in refractory metal alloys, thereby contributing to an in-depth understanding of the state-of-the-art, and establishing a base line for further research, development, and application.

This Symposium is fifth in a series of conferences on refractory metals, sponsored by the Metallurgical Society of AlME. Publications issuing from the conferences are valuable technical and historical source books, tracing the evolution of refractory metals from early laboratory alloying studies to their present status as useful engineering materials. Refractory metals are arbitrarily defined by melting point. A melting temperature of over 35000 F was selected as the minimum for this Symposium, thus excluding chromium and vanadium, which logically could be treated with other refractory metals in Groups VA and VIA of the periodic table. The Refractory Metals Committee is planning reviews of chromium and vanadium in subsequent conferences. Of eleven metals with melting points above 35000F, four have been advanced significantly in recent years, as bases for structural alloys, namely Cb, Mo, Ta, and W. The remaining seven (Re, 8f, Ir, Rh, Ru, Tc and Os) have received lesser development, a fact reflected in the Sympo• sium program. Perhaps future Symposia will show a different emphasis.

At the time of the first High Temperature Materials Conference in 1957 (Cleveland, Ohio) only the Mo-O.5% T1 alloy was in commercial pro• duction. Currently (1968) several dozen useful Cb, Mo, Ta, and W alloys have evolved, with many obtainable in good quality as sheet, foil, tube, wire, bar, and forgings. Although complete information on aerospace, nuclear, and commercial applications was not available for presentation at the SympoSium, it appears that refractory metals are serving essential structural functions, predominantly in prototype studies of propulsion, power generation, and hypersonic flight devices, with few requirements involving large quantities. A major factor limiting the utility of refractory metals in high temperature processes continues to be the lack of alloys (coated or otherwise) reliably operable for long times (multi-hundreds ofbours) in oxidizing environments. Nonetheless, there are several environments in which refractory metals are optimum materials, including vacua, inert gases, and liquid alkali metals. In oxidizing environments coated re• frac~ory metals can serve for limited periods, under appropriate con-

v vi PREFACE ditions. The U. S. capability in refractory metals for structural uses has been attained with Government support. supplemented by industry. of pro• grams ranging from basic research to fabrication of hardware. Much work remains. if desired improvements in oxidation-resistance. strength. ductility. weldability and fabricability are to be attained. However, it appears likely that research efforts. in the future, will be selectively directed towards solving those critical problems limiting the useful potential of refractory metals. The invited papers in this publication were intended to provide maximum information required in judging future needs and research directions. We are grateful to the National Aeronautics and Space Administration for support enabling us to publish these proceedings. Much credit is due to authors of papers, who have made significant professional contributions by directing many hours of their leisure time to hard work. Our thanks are also extended to session chairmen and to members of the Refractory Metals Committee. who partiCipated in organizing this Symposium. Distribution of this book in a timely and economical manner has been facilitated by photographic reproduction of authors' manuscripts, a pro• cedure necessitating some relaxation of standards for editorial uniformity and format. We trust that the advantage of timely publication will out• weigh perfection of format. It is regretted that the following planned papers were not available: Refractory Metals in Aerospace Structures, Use of Refractory Metals in Aerospace PropulSion, and Molybdenum and Moly• bdenum-Base-Alloys-Recent Developments.

April 1968 1. Hachlin R. T. Begley E. D. Weisert Contents

Basic Strengthening Mechanism in Refractory Metals ••••••••••••••• 1 B. A. Wilcox

High Temperature Creep and Fracture Behavior of the

Refractory Metals 0.0 •• 00000 •• 0.0000000.00000.0.0000 ••• 00 41 R. T. Begley, D. L. Harrod, and R. E. Gold

The Effect of Thermal-Mechanical Treatments on the Structure and Properties of Refractory Metals ••••••••••••••••••••• 85 R. A. Perkins

Interactions in Coated Refractory Metal Systems ~...... 121 A. G. Metcalfe and A. R. Stetson

Interactions of Refractory Metals with Active Gases in Vacua and Inert Gas Environments •••••••••••••••••••••••• 165 H. Inouye

Hydrogen Effects in Refractory Metals 197 W. T. Chandler and R. J. Walter

The Compatibility of Refractory Metals with Liquid Metals •••••••• 251 E. E. Hoffman and R. W. Harrison

Refractory Metals in Space Electric Power Conversion Systems ••••• 289 J. W. Semmel, Jr.

Recent Advances in Columbium Alloys 325 R. G. Frank

Considerations in the Development of Tantalum Base Alloys •••••••• 373 R. W. Buckman, Jr. and R. C. Goodspeed

Advanced Processing Technology and High Temperature Mechanical Properties of Tungsten Base Alloys ••••••••••••••••••••• 395 H. G. Sell

vii viii CONTENTS

The Less Common Refractory Metals (Rhenium, Technetium, Hafnium, Noble Metals) ••••••••••••••••••••••••••••••••••• 451 J. Maltz

Index 0 0 •• " 0 •••••• 0 • 0 " ••••• " • 0 0 • " 0 • 0 •• " 0 0 " 0 • 0 0 " •••• 0 0 0 0 •••• 0 0 " 0 •• 0 489