The microstructure of Co-Cr-Mo-(Nb) dental alloys

SEM and TEM investigations carried out on a model dental casting alloy containing 0.4% C, 30% Cr, 5% Mo and the rest Co, and a similar alloy also containing 1% Nb which is suitable for blending with ceramic material, have shown that the apparently two phase microstructure observed under the optical...

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Bibliographic Details
Published inPraktische Metallographie Vol. 38; no. 9; pp. 514 - 531
Main Authors Kulmburg, A, Kvas, G, Wiedner, G, Golob, P, Warbichler, P, Schmied, M, Bratschko, R O
Format Journal Article
LanguageEnglish
German
Published 01.09.2001
Subjects
Eutectics
Metal castings
Metallographic microstructure
Scanning electron microscopy
Ternary systems
Transmission electron microscopy
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Summary:SEM and TEM investigations carried out on a model dental casting alloy containing 0.4% C, 30% Cr, 5% Mo and the rest Co, and a similar alloy also containing 1% Nb which is suitable for blending with ceramic material, have shown that the apparently two phase microstructure observed under the optical light microscope is in fact much more complex that at first thought. From the energy filtered TEM pictures it was able to show that in both alloys, in addition to a block shaped sigma -phase, an extremely fine eutectic also exists which consists of a Co-rich solid solution together with M sub(23)C sub(6) and M sub(6)C carbides. In addition, also arranged within the eutectic, the niobium containing alloy also contains extremely fine niobium carbonitrides. As a result of discovery of this extremely fine ternary eutectic, it is now possible to explain the extremely good casting properties of these two alloys.
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ISSN:0032-678X