Nilo® K

A Nickel-Iron-Cobalt, controlled expansion alloy containing nominally 29% Nickel and 17% Cobalt. Its coefficient of expansion (which decreases with rising temperature to the inflection point), matches the expansion rate of borosilicate glasses and alumina ceramics.

Nilo® K is also known as Kovar, Dilver, and Pernifer 2918.

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Chemical Composition

Element	Min %	Max %
Fe	53.00 nominal
Ni	29.00 nominal
Co	17.00 nominal
Mn	–	0.50
Si	–	0.20
C	–	0.04
Al	–	0.10
Mg	–	0.10
Zr	–	0.10
Ti	–	0.10
Cu	–	0.20
Cr	–	0.20
Mo	–	0.20

Alloy Details

Nilo® K density, melting point, inflection point, thermal conductivity, and coefficient of expansion is indicated in the table below:

Density	Melting Point	Inflection Point	Thermal Conductivity	Coefficient of Expansion
8.16 g/cm³	1450 °C	450 °C	16.7 W/m• °C	6.0 µm/m °C (20 – 100 °C) 4.6 – 5.2 µm/m °C (20 – 400 °C)
0.295 lb/in³	2640 °F	840 °F	116 btu•in/ft²•h °F	3.3 x 10^-6 in/in °F (70 – 212 °F) 2.6 – 2.9 x 10^-6 in/in °F (70 – 752 °F)

Heat treatment of finished parts

The Nilo® alloys are usually supplied and used in the annealed condition (residual cold work distorts the coefficients of thermal expansion). Annealing times may vary due to section thickness.

The typical heat treatment of Nilo® K:

	Type	Temperature	Time	Cooling
	Anneal	850 – 1000 °C (1560 – 1830 °F)	0.5 Hr	Air or water
To prepare for glass to metal sealing	Decarburization	900 – 1050 °C (1650 – 1920 °F)	1 Hr	Air or water
If a metal oxide interface is required (time and temperature depend on required oxide thickness)	Oxidize	600 – 1000 °C (1110 – 1830 °F)	1 Hr	Air