A Nickel-Iron-Cobalt, controlled expansion alloy containing 29% Nickel. 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.
| 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 |
Density
8.16 g/cm³ | 0.295 lb/in³
Melting Point
1450°C | 2640°F
Modulus of Rigidity
16.7 W/m•°C | 116 btu•in/ft2•h°F
Modulus of Elasticity
6.0 µm/m °C (20 – 100°C) 4.6 – 5.2 µm/m °C (20 – 400°C) | 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
| Type | Temperature | Time (Hr) | Cooling | ||
| °C | °F | ||||
| Anneal | 850 – 1000 | 1560 – 1830 | 0.5 | Air or water | |
| To prepare for glass to metal sealing | Decarburization | 900 – 1050 | 1650 – 1920 | 1 | Air or water |
| If a metal oxide interface is required (time and temperature depend on required oxide thickness) | Oxidize | 600 – 1000 | 1110 – 1830 | 1 | Air |
Properties
| Condition | Approx. tensile strength | Approx. operating temperature | ||
| N/mm² | ksi | °C | °F | |
| Annealed | 450 – 550 | 65 – 80 | up to +400 | up to +750 |
| Hard Drawn | 700 – 900 | 102 – 131 | up to +400 | up to +750 |
| Condition | Approx. tensile strength | Approx. operating temperature | ||
| N/mm² | ksi | °C | °F | |
| Annealed | 450 – 550 | 65 – 80 | up to +400 | up to +750 |
| Hard Drawn | 700 – 900 | 102 – 131 | up to +400 | up to +750 |