High-Temperature Metallizing of Alumina

  • M. E. Twentyman
  • P. Hancock
Part of the Materials Science Research book series (MSR, volume 14)


In the high-temperature metallizing process a thin layer of molybdenum paint is fired on to the surface of a debased alumina so that the alumina can be brazed to a metal component. During the firing, glass from the alumina migrates into the molybdenum layer and helps it to adhere to the alumina. In general it is desirable to form a dense glass/metal composite structure in order to form a strong seal. Fig. 1. shows a typical seal structure. Tensile-strength measurements on such seals often result in the seals failing in the alumina and it is sometimes suggested that the seal is therefore stronger than the alumina. This is a rather loose interpretation as seals which fracture in the alumina may cover a very wide range of strengths depending upon the seal components and process conditions. One example of strength variation was described in a previous paper1 in which it was found that ASTM2 test-pieces metallized at 1400°C failed in the alumina at an average tensile stress of 43 MN/m2 compared with an average of 71 MN/m2 for samples metallized at 1500°C. Fairly large variations in strength have also been reported by other workers. Thus Cole and Hynes3 found that the average strength of samples metallized with a Mo/Mn paint was 55 MN/m2 compared with 83 MN/m2 for a Mo/Ti paint.


Metal Component Metallizing Layer Braze Alloy Average Tensile Stress Molybdenum Powder 
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  1. 1.
    M.E. Twentyman and P. Popper, “High Temperature Metallizing, Part 2”, J. Mat. Sci. 10:777 (1975).CrossRefGoogle Scholar
  2. 2.
    American Society for Testing Materials, ASTM F19-64 (Reapproved 1971).Google Scholar
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    S.S. Cole and F.J. Hynes, “Some Parameters Affecting Ceramic-to-Metal Seal Strength of a High-Alumina Body”, Bull. Am. Ceram. Soc. 37:135 (1958).Google Scholar
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    M.E. Twentyman and P. Hancock, “High-Temperature Metallizing, Part 4: The Effect of Seal Composition on the Strength of Metal-Alumina Seals”, Research Paper 712, British Ceramic Research Association (1980).Google Scholar
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    W.H. Kohl, “Materials and Techniques for Vacuum Devices”, New York Reinhold, (1967).Google Scholar
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Copyright information

© Plenum Press, New York 1981

Authors and Affiliations

  • M. E. Twentyman
    • 1
  • P. Hancock
    • 1
  1. 1.British Ceramic Research AssociationStoke-on-TrentEngland

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