Metals & alloys · Nickel & cobalt alloys
Kovar controlled-expansion alloy
A nickel–cobalt–iron alloy engineered to match the thermal expansion of borosilicate glass and alumina for hermetic electronic packages.
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01
Overview
- Material class
- Metals & alloys
- Category
- Nickel & cobalt alloys
- Family
- Controlled-Expansion Alloy
- Product forms
- Sheet/plate, Bar/rod
Composition
| Constituent | Min | Max | Typical | Note |
|---|---|---|---|---|
| Ni | 28.5 | 29.5 | 29 | |
| Co | 16.8 | 17.8 | 17 | |
| Mn | 0.5 | 0.3 | ||
| Si | 0.2 | 0.1 | ||
| Fe | Balance |
02
Properties and conditions
Engineering properties
| Property | Value | Unit | Condition |
|---|---|---|---|
| Density | 8.36 | g/cm³ | Representative; verify product form and condition |
| Elastic modulus | 138 | GPa | Representative; verify product form and condition |
| CTE | ~5.0 | µm/m·K | 30–400 °C |
| Thermal conductivity | ~17 | W/m·K | Representative; verify product form and condition |
| Curie temperature | ~435 | °C | Representative; verify product form and condition |
| Yield strength | ~240–450 | MPa | condition dependent |
Conditions
Representative supplied condition
Condition not fully specified in the source record.
03
Processing and use
Processing
- Surface oxidation and pre-seal thermal treatment are controlled to form adherent glass bonds.
- Cold work alters expansion and should be relieved before sealing.
Applications
- Hermetic packages
- Feedthroughs
- Microwave tubes
- Sensors
Selection considerations
- Use only with compatible glass or ceramic expansion systems.
- Cobalt and nickel exposure drives cost and sourcing risk.
Open in an analysis tool
04
Standards and related materials
Standards and designations
| System | Designation | Note |
|---|---|---|
| UNS | K94610 | |
| ASTM | F15 | |
| Trade | Kovar |
05
Sources and context
Sources
- Carpenter Kovar alloy data sheetExisting reference
- ASTM F15Existing reference
- U.S. Department of Energy critical materials programStrategic reference
Confirm the applicable specification, product form and condition before using values for design or procurement.
Supply and sustainability
Available as strip, sheet, wire and machined package stock from specialty mills.
Small component mass but high-value alloying; recovery is challenging from complex electronic assemblies.
Strategic context
Critical packaging alloy for reliable glass-to-metal and ceramic-to-metal seals in electronics and vacuum systems.
Critical inputs: Nickel, Cobalt
Basis: EU Critical Raw Materials Act (2024); USGS 2025 Critical Minerals List