Kovar
UNS K94610
Description
Kovar alloy is a nickel-iron-cobalt, controlled expansion alloy whose chemical composition is controlled within narrow limits to assure precise uniform thermal expansion properties. It has substantially the same thermal expansion characteristics as borosilicate glass (~5 x 10-6 /K between 30 and 200 °C, to ~10 x 10-6 /K at 800 °C), which can allow a tight mechanical joint between Kovar and borosilicate glass over a range of temperatures. Thus, it is an ideal alloy for use in high integrity glass-to-metal and ceramic-to-metal seals. In addition, Kovar is also a good coefficient of thermal expansion match for many other materials, including aluminum nitride, shapal, germanium, and sapphire.
Chemical Component
| Ni | Co | Fe | C | Mn | Si |
|---|---|---|---|---|---|
| 29% | 17% | Balance | 0.04% | 0.5% | 0.2% |
Basic Information
| Items | Kovar |
|---|---|
| Catalog | ACMA-Ni-A003 |
| Density | 8.26 g/cm3 |
| Modulus of Elasticity at 20 °C | 207 MPa |
| Specific Heat | 0.11 J/g- °C |
| Thermal Conductivity at 20 °C | 17.3 W/m.k |
| Thermal Expansion | 0.17 W.m-1°C |
| Electrical Resistivity | 49 mm2/m |
| Poisson's coefficient | 0.317 |
| Curie Temperature | 815 °F (435 °C) |
| Melting Point | 2640 °F (1449 °C) |
Material Forms
Alfa Chemistry offers Kovar in a variety of forms, including
- Wire
- Tube
- Pipe
- Round Bar
- Sheet & Coil
Mechanical Properties
| Condition | Yield Strength | Tensile Strength | Hardness | Elongation |
|---|---|---|---|---|
| Annealed, Descaled | 40 KSI (276 MPa) | 75 KSI (518 MPa) | 78 HB | >20 |
Features
- Expansion Control: Reliable hermetic sealing applications
- Uniformity: Precise and uniform thermal expansion characteristics
- Shock-resistant: Their coefficient thermal expansion makes the seal resistant to shock and cracking
Specifications
Wire, Tube, Pipe, Round Bar, Sheet & Coil: ASTM F15, AMS I-23011 CL1, Workstoff 1.3981, UNS K94610
Applications
Kovar can be used in a variety of applications, including:
- Hermetic sealing
- Production of transistors and diodes in electronic industry
- Vacuum systems in chemistry and scientific research
- Electronic tubes (power, X-Ray)
- Hybrid circuit casings
- Oscillator housings
- Concentrated solar power
- Scientific instruments
* Technical data included herein should be used as a guideline only, and should not be construed as maximum or minimum values for specification or for final design, or for a particular use or application. The data may be revised anytime without notice.
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