Kovar Alloy UNS K94610: Properties and Applications

# Kovar Alloy UNS K94610: Properties and Applications

## Introduction to Kovar Alloy UNS K94610

Kovar alloy, designated as UNS K94610, is a nickel-cobalt ferrous alloy specifically designed to have a thermal expansion coefficient that closely matches that of hard (borosilicate) glass. This unique property makes it invaluable in applications where metal and glass need to be sealed together without causing stress or cracking due to thermal expansion mismatch.

## Composition and Properties

The typical composition of Kovar alloy (UNS K94610) is:

– Nickel (Ni): 29%
– Cobalt (Co): 17%
– Iron (Fe): Balance
– Small amounts of manganese (Mn), silicon (Si), and carbon (C)

### Key Properties:

– Low thermal expansion coefficient (≈5.3 × 10⁻⁶/°C between 30-200°C)
– Excellent glass-to-metal sealing characteristics
– Good mechanical strength
– Corrosion resistance
– Magnetic properties similar to iron

## Manufacturing Process

Kovar is produced through vacuum induction melting followed by hot working processes. The material can be formed using standard metalworking techniques, including:

– Machining
– Welding (using matching filler metal)
– Cold working
– Annealing (typically at 800-850°C)

## Applications of Kovar Alloy

Due to its unique properties, Kovar finds applications in various industries:

### Electronics and Telecommunications

– Glass-to-metal seals in vacuum tubes
– Transistor and diode packages
– Microwave tubes
– X-ray tubes

– Hermetic seals for electronic components

### Aerospace and Defense

– Satellite components
– Radar systems
– Missile guidance systems

### Scientific Instruments

– Particle accelerators
– Laser systems
– High-vacuum equipment

## Advantages Over Other Materials

Kovar offers several advantages compared to other sealing alloys:

– Better thermal expansion match with borosilicate glass than pure metals
– Lower cost than some alternative alloys
– Established manufacturing processes
– Proven reliability in critical applications

## Limitations and Considerations

While Kovar is an excellent material for many applications, there are some limitations to consider:

– Not suitable for sealing with all types of glass
– Requires careful cleaning before glass sealing
– Can be subject to hydrogen embrittlement in certain environments
– Higher cost than standard steel alloys

## Future Outlook

The demand for Kovar alloy is expected to remain stable as it continues to be the material of choice for many glass-to-metal sealing applications. Research is ongoing to develop alternative materials with similar properties but potentially lower costs or improved performance characteristics.