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Alloy K (Kovar®) Controlled Expansion Alloy

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1.3981 (FeNi29Co17) is an iron-nickel-cobalt alloy whose chemical composition is controlled within narrow limits to ensure precise and uniform thermal expansion and mechanical characteristics. These properties make it an ideal alloy for use in high integrity glass-to-metal and ceramic-to-metal seals, particularly where the application requires resistance to thermal shock. It shows the following features and properties:

  • Uniform thermal expansion characteristics
  • Related Standards

    Equivalent Materials

    This material data has been provided by Matmatch.

    All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
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    23.0 °C

    8.25 g/cm³

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    Elastic modulus

    23.0 °C

    139 GPa

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    23.0 °C

    30 %

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    Hardness, Vickers

    23.0 °C

    160 [-]

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    Tensile strength

    23.0 °C

    540 MPa

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    Yield strength

    23.0 °C

    380 MPa

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    Coefficient of thermal expansion

    30.0 °C

    4.6E-6 1/K

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    450.0 °C

    5.5E-6 1/K

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    Melting point

    1450 °C

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    Specific heat capacity

    23.0 °C

    500 J/(kg·K)

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    Thermal conductivity

    23.0 °C

    17 W/(m·K)

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    Chemical properties



    17 %

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    53 %

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    29 %

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    Technological properties

    Application areas

    General: Power and microwave tubes, transistors and diodes, lids and closures in a variety of hybrid electronic circuit packages.