Kovar Material Properties

Kovar is an iron-nickel-cobalt low expansion alloy. By controlling the chemical composition within narrow limits, precise and uniform thermal expansion properties are assured.

With a linear expansion coefficient equal to that of glass and ceramics, Kovar is used for applications requiring a high reliability glass-to-metal or ceramic-to-metal seal with either Pyrex or borosilicate glass and alumina-type ceramic materials. This is particularly useful where resistance to thermal shock is a requirement.

Kovar alloy is magnetic at all temperatures below the Curie point. Magnetic properties are dependent on heat treatment; the lower the hardness, the higher the permeability values.

Applications: Hermetic seals, high-power transmitting valves, transistor leads and headers, integrated-circuit lead frames.


Density .302 lb/in3
Specific Gravity 8.36
Melting Point 2640 °F
Curie Temp 815 °F
Composition Fe 53%, Ni 29%, Co 17% all nominal
Mn, Si, C, Cr, Cu, Mo, Al, Mg, Zr, Ti
Tensile Strength 75,000 PSI
Yield Strength 50,000 PSI
Young’s Modulus 20 x 106 PSI
Thermal Conductivity 120 BTU-in/sq.ft/hr/°F@77°F
Thermal Expansion 2.9 ppm/°F (75°F to 842°F)
Specific Heat 0.11 BTU/lbm · °F
Electrical Resistivity 49 µΩ·cm