Proceedings of the International Forum on Structural Ceramics Joining Symposium Chairs: Ronald E. Loehman, Sandia National Laboratories Sylvia M. Johnson, SRI International Arthur J. Moorhead. Oak Ridge National Laboratory A Collection of Papers Presented at the International Forum on Structural Ceramics Joining Sponsored by the Engineering Ceramics Division The American Ceramic Society, Inc. April 26-30, 1987 Pittsburgh, PA ISSN 0196-6219 Published by The American Ceramic Society, Inc. 757 Brooksedge Plaza Drive Westerville, OH 43081-6136 Copyright@ 1989, The American Ceramic Society, Inc. Erectrtive Director & Ptthlislier Editor W. Paul Holbrook John B. Wachtman Director of Publications Pmdticlion Mnmger Linda S. Lakemacher Alan Hirtle Committee on Ptrhlicntionc David W. Johnson, Jr., chair; Ronald E. Loehman; Richard E. Tressler; Robert J. Eagan, ex officio;W . Paul Holbrook, ex oficio; Waltraud M. Kriven, a oficio; John B. Wachtman, ex oficio. Editorial and Subscription OJJ7es: 757 Brooksedge Plaea Drive, Westerville, Ohio, 43081-6136. Subscription $60 a year; single copies $15 (postage outside U.S. $5 additional). Published bimonthly. Printed in the United States of America. Allow four weeks for address changes. Missing copies will be replaced only if valid claims are received within four months from date of mailing. Replacements will not be allowed if the subscriber fails to notify the Society of a change of address. CESPDK Vol. 10, NO. 11-12, pp. 1503-1950, 1989 The American Ceramic Society assumes no responsibility for the statements and opinions advanced by the contributors to its publications, or by the speakers _____ ~~ Copyright Q 1989, by the American Ceramic Society. Permission to photocopy for personal or internal use beyond the limits of Sections 107 and 108 of the U.S. Copyright Law is granted by the American Ceramic Society for libraries and other users registered with the Copyright Clearance Center, provided that the fee of $2.00 per copy of each article is paid directly to CCC, 21 Congress Street, Salem, MA 01970. The fee for articles published before 1989 is also $2.00 per copy. This consent does not extend to other kinds of copying, such as copying for general distribution, for advertising or promotional purposes, or for creating new collective works. Requests for special permission and reprint requests should be addressed to the Technical Editor, the American Ceramic Society (0196-6219/88 Each issue of Ceramic Engineering and Science Proceedings includes a collection of technical articles in a general area of interest, such a~ glass, engineering ceramics, and refractories. These articles are of practical value for the ceramic industries. The issues are based on the proceedings of a conference. Both The American Ceramic Society, Inc., and non-Society conferences provide there technical articles. Each issue is organized by an editor who selects and edits material from the conference. Some issues may not be complete representations of the conference proceedings. There is no other review prior to publication. I 1 Preface Although joining methods for structural ceramics have been investigated since the early development of advanced ceramics, it is only in the last few years that the importance of joining to the practical success of these materials has been recognized. Reliable joining methods are not only critical for compo- nent and system assembly, but they are also required for repair technology. The heightened awareness of joining as an integral part of the fabrication pro- cess for advanced ceramics is reflected in its present increased level of research and development activity. Against this backdrop, the Engineering Ceramics Division of the American Ceramic Society sponsored a two day International Forum on Structural Ce- ramics Joining at its 89th Annual Meeting in Pittsburgh, PA, April 28-29, 1987. The Forum featured forty-two oral presentations by scientists and en- gineers throughout the world. In fact, more than one third of the speakers were from outside the United States emphasizing the truly international scope of ceramic joining work. Bringing together such a distinguished group of researchers on ceramic joining provided a valuable forum at which the state of the art and its future directions could be discussed. This issue comprises the papers that were submitted for publication by the Forum paticipants and which were then peer-reviewed according to the nor- mal procedures of the American Ceramic Society. We have arranged the proceedings into four sections to present a logical progression of topics. Thus, the papers in the first section deal with fundamental studies of interfaces and with investigations of model ceramic-metal systems, as exemplified by the pa- per on Pd/A120, interfaces by Eastman and Ruhle. The second section con- tains the papers concerned with interfacial reactions between brazing filer metal alloys and structural ceramics such as Si,N,, SIC, and Zr02. The common thread that ties together most of those papers is their focus on the high tem- perature chemistry of interfacial reactions relevant to joining. The third sec- tion groups the papers that report development of practical joining methods for structural ceramics. The last section of the book contains the papers deal- ing primarily with strength, mechanical properties, and durability of struc- tural ceramic joints. The results of those papers have a common dependence on studies such as those presented in the first three sections; that is, in order to make strong, reliable joints with any degree of control, one must under- stand the structure and chemistry of the interface. Thus, this book forms a more coherent whole than one ordinarily finds in a volume assembled from a collection of presentations at a scientific meeting. We appreciate the efforts of the speakers and their co-authors for their presentations at the Forum, and, particularly, for providing the manuscripts that made this volume possible. We also wish to acknowledge the organiza- tional and editorial support of the staff of the American Ceramic Society in the production of this volume. Ronald E. Loehman Sylvia M. Johnson Arthur J. Moorhead Table of Contents Model Systems Ultrahigh Vacuum Diffusion Banding of Metals to ..................................... Ceramics 1503 B. Gibbesch, G. Elssner, W. Mader, and H. Fischmeister ................ TEM Studies of Pd/A1a3 Interfaces 15 15 J. A. Eastman and M. Riihle ........ Spinel Formation in the Nickel-Alumina System 1531 H.S. Betrabet, S.N.S. Reddy, S. Purushothaman, and I. Reimanis ........ Crystallographic Study of Ceramic-Metal Joints 1541 Shotaro Morozumi and Michio Kikuchi Material Transport Mechanisms During the .............. Diffusion Bonding of Niobium to A1203 1549 K. Burger and M. Rahle ............ Intrusion Bonding of Nickel and Zirconia 1567 I. E. Reimanis, S. L. Shinde, and L. C. DeJonghe ................ Alumina-Copper Diffusion Bonding 1575 R. M. Crispin and M. G. Nicholas Bonding and Fracture of Titanium-Containing Braze ........................... Alloys to Aluminum 1582 Roger T. Cassidy, Russell E. Pence, William E. Moddeman, and Anthony D. Buonaquisti Interfacial Reactions ...... Brazing Ceramics with Alloys Containing Titanium 1602 M. G. Nicholas and R. M. Crispin ........ Brazing Alloy Design for Metal/Ceramic Joints 1613 Rakesh R. Kapoor and Thomas W. Eagar ........................ Joining Nitride Ceramics 1631 A. P. Tomsia, J. A. Pask, and R. E. Loehnian Wetting of Silicon Nitride with Selected Metals and ..................................... Alloys 1655 Lennart Ljungberg and Richard Warren An Investigation of Interfacial Microstructure and Bonding in Brazed Silicon Nitride-Silicon Nitride ........ and Silicon Nitride-Ne-Cr-Fe Alloy 600 Joints 1667 S. C. Hsu, E. M. Dunn, K. Ostreicher, and T. Emma .......... Interfacial Reactions in Metal-Sia, Bonding 1685 R. K. Brow and I<, E. Loehman Interface Mixing Between Metals and Ceramics: ....... Classification, Thermochemistry, and Processing 1696 S. N. S. Reddy, H. S. Betrabet, S. P. Purushothaman, and C. Narayan Morphological Development of Zirconia-Metal ................................... Interface 1708 B. S. Chiou, Y. C. Wu, and J. G. Duh Interfacial Reaction Between Zirconia and Carbon ...................................... Steel 1722 Nobuya Iwamoto, Yukio Makino, and I-Iajime Yokoo Wetting of Silicon Carbide Surfaces by .................... Mg0-Li@-AI@,-SiO2 Glasses 1735 Dennis N. Coon and Robert M. Neilson, Jr. Joining Methods ....... Joining Between Zirconias Using Platinum Metal 1745 Nobuya Iwamoto, Yukio Makino, and Tokio Sera Joining Silicon Carbide Using Nickel- Active Metal .................... (or Hydride) Powder Mixtures 1761 Nobuya Iwamoto, Yukio Makino, and Hiroshi Miyata Silicon Nitride Joining with Glasses in the System .................................. CaO-SiO, 1768 Yukio Haibara, Norimasa Unicsaki, and Nobuya Iwamoto Strength and Fracture ........ The Strength of Ceramics Bonded With Metals 1786 B. J. Dalgleish, M. C. Lu, and A. G. Evans .......... Modeling of Ceramic to Metal Brazed Joints 1801 Pierre 0. Charreyron, Donald 0. Patten, Jr. and Bradley J. Miller Boundary Effects on the Interfacial Transient ......... Thermal Fracture of Ceramic-To-Metal Bonds 1825 Klod Kokini ......... Mechanical Behavior of Brazed Silicon Nitride 1846 Sylvia M. Johnson Comparison of Strengths of Active Metal Brazements in Alumina and SIC Whisker- ........................... Reinforced Alumina 1853 A J. Moorhead and Hyoun-Ee Kim ..... Mechanical Behavior of Ceramic-Metal Braze Joints 1866 Donald 0. Patten, Maurice L. Torti, and Pierre 0. Charreyron ......... Ultrasonic Characterization of Ceramic Joints 1879 W. A. Simpson, Jr. and R. W. McClung Strength of Silicon Nitride-Silicon Nitride Joints .................... Bonded With Oxynitride Glass 1893 Robert M. Neilson, Jr. and Dennis N. Coon Effect of Testing Atmosphere on Mechanical ................. Properties of Ceramic/Metal Joints 1908 K Suganuma, M. Morita, T. Okamoto, and M. Koizumi Effect of Surface Grinding Conditions on Strength ....................... of Alumina/Niobium Joint 1919 K. Suganuma, T. Okamoto, M. Koizumi, and S. Gohda ................................ Author Index 1935 ............................... Subject Index 1943 Ceramic Engineering and Science Proceedings Ronald E. Loehman, Sylvia M. Johnson, Arthur J. Moorhead copyright 0 1989, The American Ceramic Society, Inc. Ceram. Eng. Sci. Proc. 10[11-121 pp. 1503-1514 (1989) Ultrahigh Vacuum Diffusion Bonding of Metals to Ceramics B. GIBBESCHG,. ELSSNERW, . MMER, AND H. FISCE~MEISTER Max-Planck-Institut fur Metallforschung Institut fur Werkstoffwissenschaften Seestrasse 92 7000 Stuttgart 1 Federal Republic of Germany A UHV apparatusf or solid-state bonding of ceramic and metal single crystal and polycrystaUine materials is described. The apparatus is especiauy designed for the production of clean integaces in bicrystal joints between crystabgraphically preoriented fit crystal plutelets. Sandwich-like pieces of 35 mm maximum height and a welded surface area of 10 mm x 15 mm can be manufactured in the apparatus which is subdivided into a cleaning chamber, a parking station, and a welding unit. The maximum welding temperature is 1800°C. Information is given on the preparation of single crystals for diflusion bonding. First experiments in the UHV bonding of polycrystalline Nb to polycrystalline alumina are described. Introduction The development of high performance structural ceramics together with considerable advances in the application of bonded ceramic-metal components in the areas of high temperature technology, energy conversion, automotive engines, microelectronics, and biomedical implants have intensified fundamental and applied research on the nature of metal-ceramic interface and their influence on the properties of the composite system. Among the various techniques available for fabricating joints,' high vacuum diffusion bonding is especially suited for studies of the structure and chemistry of metal ceramic interfaces and their interrela- tion to the properties of the interface region and the joint. Sandwich- like specimens of the configuration ceramic-metal-ceramic offer the possibility to investigate in a rather simple manner transport pheno- mena at and across interfaces, interfacial and bulk chemical reactions, dimensional changes and the development of defects in the interface regions of single crystals or polycrystalline materials and their depen- dence on parameters such as bonding temperature, time, mechanical 1503 pressure, vacuum pressure, surface roughness, and specimen dimen- sions. Moreover, specimens cut from diffusion bonded pieces can be thinned to TEM foils for examination by conventional, STEM, and HREM technique^.^-^ Likewise, bend test specimens can be manufac- tured to determine mechanical properties of the joint such as bond strength, fracture resistance, and interface fracture energy.’-’ A considerable drawback of conventional diffusion bonding is the restriction to a high vacuum of the order of 10” mbar. Bonding behavior and interface chemistry depend critically on the cleanliness of the surfaces to be bonded and hence both on the surface cleaning procedures and the vacuum pressure prior to and during the bonding process as shown, e.g., by experiments of Pepper on the strength of metal-sapphire interfaces.’ In the last decade, ultrahigh vacuum techniques have been developed to produce clean interfaces in artificially bonded bicrystals manufactured from two separate crystals and to study the bonding behavior of metal and metal-ceramic single crystal and polycrystalline combinations. These experimental studies took advantage of ion sputter techniques to clean the surfaces of ultrahigh vacuum conditions to maintain their cleanliness. Ruge and co- constructed a UHV apparatus to investigate solid-state bonding between polycrystalline metals and of metal-to-ceramic combinations at room temperature. The UHV chamber is equipped with a tension and compression device of 1000 N maximum load in order to rupture and to reweld notched specimens by solid-state bonding of their cleaved or fractured surfaces. A residual gas analyzer was employed to determine the gaseous species that are present. The attainable vacuum was 2 x mbar.” Milkove and Sass” used a UHV apparatus for the preparation of thin metal bicrystals containing clean grain boundaries. A specimen preparation jig within the UHV chamber served to manufacture [OOI] metal twist boundaries by epitaxial metal deposition onto two cleaved and preoriented NaCI crystals and subsequent pressing of the coated crystals films. A residual gas analyzer was employed to monitor the composi- tion of the gaseous species during the different preparation stages. Akaike and Funakubo” studied the cold pressure welding behavior of A1/A1203a nd metallmetal combinations under UHV conditions. They used spherical test specimens which were indented into a single crystal metal plane. Prior to indentation, the specimens were cleaned by argon ion bombardment. The apparatus was later designed to allow solid- state welding of flat plate/plate configuration^.'^ UHV techniques and ion beam cleaning procedures are also used in studies of the shear strength’ and the adhesion, friction, and wear properties of sin le crystal and polycrystalline ceramic/metal and metal/metal pairs. 1F-17 Prior to the friction experiments and after argon-ion bombardment, the cleanliness of the surfaces of the flat ceramic specimen and of the pin- like metal specimens is controlled by means of Auger electron spectro- metry. 1504 The present paper reports on an ultrahigh vacuum apparatus designed for the preparation of ceramic-metal bicrystals and polycrys- talline ceramic-metal joints by diffusion bonding under well defined conditions of cleanliness, interface crystal orientation, temperature, time, vacuum, and mechanical loading. In this first report the UHV apparatus and the specimen preparation procedure will be described. Furthermore, some information is given on UHV diffusion bonding experiments in which polycrystalline Nb platelets and alumina pieces were manipulated and welded to test the functions of the new UHV apparatus. Ultrahigh Vacuum Apparatus The apparatus for solid-state bonding of metals to ceramics is subdivided into three parts (Fig. 1): the cleaning chamber, the parking station, and the welding chamber. These units are so interconnected that a transfer of the specimens via a linear motion transporter is possible. The chambers are separated by gate valves and individually evacuated to retard recontamination of the surfaces of the specimens. The cleaning and the welding chamber are each mounted on a Leybold- Heraeus vacuum system with a Ti sublimation pump of 1200 I/s pumping speed, a turbomolecular pump of 345 I/s pumping speed, and a rotary vane pump of 15.5 m3/h pumping speed. The vacuum of the parking station is maintained by a sputter ion pump. Cleaning Chamber In order to obtain clean and precisely oriented interfaces the entire manipulation of the metal and ceramic specimens which are to be solid- state bonded is carried out under UHV conditions after the specimens have been introduced into the chamber. In the first series of experiments the specimens were positioned by hand onto the parking carousel of the opened chamber. This procedure will be replaced by an introduction of specimens from normal atmo- sphere into the UHV chamber via a sample inlet system with a fast entry and exit lock to enable a continuous operation of the welding unit. After closing the chamber it was baked out at a temperature of 250°C for at least 12 h to achieve a vacuum pressure of 2 x mbar. The chamber is equipped with a Leybold-Heraeus scanning ion gun IQE 12/63, an LH Q 100 residual gas analyzer, which operates over a mass range of 1-100 amu, and an ionization gauge for total vacuum pressure measurements. An Auger spectrometer will be added to the cleaning chamber in the near future. The parking carousel of 160 mm diameter holds 16 sample holders. By rotation and vertical shifting of the carousel the surfaces of the flat specimens are adjusted to the appropriate working distances for argon- ion sputtering or Auger analysis. The latter will be used for the chemical characterization of the surfaces to be bonded. During the 1505 cleaning operation the ion beam scans the entire specimen surface of dimensions 10 x 15 mm2. The ion energy can be varied from 500 eV to 5 keV. The working pressure during the sputter process is 5 x lo4 mbar. The cleaning of one surface takes about 30 min. If necessary, the specimen can be turned through 360°C with a magnetic motion lead-through to enable the cleaning of the opposite specimen surface. A wobble stick equipped with a fork grip is used to lift and carry the cleaned specimens to the linear motion sample transporter. Parking Station The linear sample transport unit consists of a carriage which is guided by two cylindrical rails and moved by a bevel-gear drive which can be actuated from the outside. To avoid recontamination during subsequent cleaning operations the carriage is positioned together with the specimen at the parking station which can be separated from the adjacent chambers by gate valves. The parking station is only used to store cleaned specimens prior to welding. Its vacuum pressure is controlled by an ionization gauge. The carriage is large enough to transport several cleaned specimens of 35 mm maximum length. Welding Chamber This part of the apparatus is designed for solid-state welding of sandwich-like configurations of the three-layer sequence ceramic- metal-ceramic or the five layer arrangement ceramic, metal, ceramic, metal, ceramic. When single crystalline materials are to be welded the latter configuration is preferred. An intermediate triple layer of single crystal discs of approximately 1 mm thickness is enclosed by two polycrystalline ceramic pieces of the dimensions 15 x 10 x 10 mm3. The welding chamber is placed in a mechanical loading jig. Alumina anvils are attached to the ends of the upper and lower steel rods through which the bonding force can be applied to the specimen configuration which is placed between the anvils. The leadthroughs of the steel rods are sealed against the atmosphere by stainless steel bellows which allow a total linear motion of 300 mm of the loaded specimens between the anvils. To enable the stacking of the cleaned specimens into the sandwich configuration, the lower anvil is moved to a position in the lower part of the welding chamber approximately opposite to the entrance port of the linear motion transporter. The cleaned specimens are then carried from the parking station to the entrance port of the welding chamber and taken from the carriage to the lower anvil by means of a wobble stick. Centering of the single specimens on the anvil is now achieved by pushing the specimens by two opposite linear motion feedthroughs. This simple arrangement will be replaced by a more sophisticated placement and orientation device for single crystals by means of which a stack of maximum five specimens can be centered and two of these 1506