Volume 4, Issue 1 (January 1976)

    A New Stable Nickel-Base Thermocouple

    CODEN: JTEOAD

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    Abstract

    The change in magnitude and direction of electromotive force (EMF) and the accompanying structural changes of nickel-chromium (Ni-Cr), nickel-silicon (Ni-Si), and nickel-silicon-magnesium (Ni-Si-Mg) alloy thermoelements at 1800°F (982°C) in air were studied in comparison with a standard type K thermocouple of the same size. The Ni-Cr versus Ni-Si-Mg couple changes only +200 µV versus +600 µV for the Type K couple after 21 200 hours at that temperature. The EMF changes of K+ and the Ni-Cr alloy are attributed to the simultaneous oxidation of Cr and Si and to the increase in oxygen. The EMF change of K- is caused by the preferential oxidation of silicon, aluminum, manganese, and iron and to the increase in oxygen. The EMF changes of Ni-Si and Ni-Si-Mg are caused by the preferential oxidation of Si and to the increase in oxygen. The presence of magnesium increases the stability of the Ni-Si system by blocking the reaction of silicon and oxygen.


    Author Information:

    Starr, CD
    Vice-President, Engineering and Research, and research directorMembers of ASTM, Wilbur B. Driver Co., Newark, N.J.

    Wang, TP
    Vice-President, Engineering and Research, and research directorMembers of ASTM, Wilbur B. Driver Co., Newark, N.J.


    Stock #: JTE10507J

    ISSN: 0090-3973

    DOI: 10.1520/JTE10507J

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    Author
    Title A New Stable Nickel-Base Thermocouple
    Symposium , 0000-00-00
    Committee E20