Chapter 53. Oxidation of Al-Containing Austenitic Stainless Steels as Related to the Formation of Strong Glass-Ceramic to Metal Seals
- John B. Wachtman Jr.
Published Online: 28 MAR 2008
Copyright © 1989 The American Ceramic Society, Inc.
A Collection of Papers Presented at the 13th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 10, Issue 9/10
How to Cite
Moddeman, W. E., Birkbeck, J. C., Bowling, W. C., Burke, A. R. and Cassidy, R. T. (1989) Oxidation of Al-Containing Austenitic Stainless Steels as Related to the Formation of Strong Glass-Ceramic to Metal Seals, in A Collection of Papers Presented at the 13th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 10, Issue 9/10 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470310588.ch53
- Published Online: 28 MAR 2008
- Published Print: 1 JAN 1989
Print ISBN: 9780470374870
Online ISBN: 9780470310588
- liquid metal infilrration process;
- aluminum alloy;
- thin-shelf spheres;
- volume fraction;
- compressive failure mechanism
Glass-ceramic to metal seals are used in pyrotechnic actuators and ignitors. Metals that have been successfully demonstrated for this application include several nickel-based alloys and a family of Al-containing austenitic stainless steels. Seals made between a lithia-alumina-silica (LAS) glass-ceramic and nickel-based alloys show excessive metal attack by the glass. This is also true of the Al-containing alloys but the etching action of the glass is less severe. This attack will cause reactions to occur at the glass-ceramic/metal interface. Not all reactions are detrimental to the seal, but some are and these unwanted reactions can cause the formation of pores and the subsequent loss of hermeticity. In this paper, LAS glass-ceramic will be sealed to Al-containing alloys that were first oxidized prior to sealing-called “preoxidation.” Results will be given that show “preoxidation” of the alloys substantially reduces the probability of glass/metal reactions during seal formation. The reduction in the amount of reaction products that are created improves the overall quality of the interface without loss of seal bond strength. In addition, the mechanism of surface oxide formation on these Al-containing steels is discussed. Auger data are presented that show the composition of the resulting oxides to be a function of the oxidation temperature. There are two theories that exist on the mechanism of oxidation; one is that oxidation occurs at the air/oxide interface (Ref. 10) and the other is that oxidation takes place at the oxide/metal interface (Ref. 11). In order to study which theory is correct for the Al-containing alloys, oxidation of the alloys was performed, first in pure 16O2, and then followed by pure 18O2, Secondary ion mass spectroscopy (SIMS) imaging results showed no layered structure but did show a mixture of oxides. Thus, the mechanism of oxidation of these alloys is not simple and must be occurring in such a manner as to allow oxygen to have access at all stages of the oxidation process.