。
# Kovar UNS K94610: Properties and Applications in Precision Engineering
## Introduction to Kovar UNS K94610
Kovar, designated as UNS K94610, is a nickel-cobalt ferrous alloy known for its unique thermal expansion properties. This specialized material was developed to match the thermal expansion characteristics of certain types of glass and ceramics, making it invaluable in applications where hermetic sealing is required.
## Chemical Composition and Physical Properties
The chemical composition of Kovar UNS K94610 typically includes:
– Iron (Fe): ~54%
Keyword: Kovar UNS K94610
– Nickel (Ni): ~29%
– Cobalt (Co): ~17%
– Trace elements: Manganese, Silicon, and Carbon
Key physical properties include:
– Density: 8.36 g/cm³
– Melting point: ~1450°C (2642°F)
– Thermal conductivity: 17.3 W/m·K (at 20°C)
– Electrical resistivity: 49 μΩ·cm
## Thermal Expansion Characteristics
Unique Thermal Matching Properties
Kovar’s most remarkable feature is its coefficient of thermal expansion (CTE), which closely matches that of borosilicate glass (such as Pyrex) and certain ceramics over a wide temperature range (typically from room temperature to 450°C). This property makes it ideal for creating reliable, stress-free seals between metal and glass components.
The average CTE of Kovar is approximately 5.1 × 10⁻⁶/°C between 30-200°C and 5.9 × 10⁻⁶/°C between 30-400°C.
## Mechanical Properties
Kovar UNS K94610 exhibits the following mechanical characteristics:
– Tensile strength: 517 MPa (75 ksi)
– Yield strength: 345 MPa (50 ksi)
– Elongation: 30% (in 50 mm)
– Hardness: 135 HB (Brinell)
– Modulus of elasticity: 138 GPa (20 × 10⁶ psi)
## Applications in Precision Engineering
Electronics and Telecommunications
Kovar finds extensive use in electronic packaging, particularly for:
- Glass-to-metal seals in vacuum tubes
- Transistor and diode packages
- Microwave and RF components
- Hermetic feedthroughs
Aerospace and Defense
The alloy’s reliability makes it suitable for:
- Spacecraft components
- Missile guidance systems
- Radar equipment
- Satellite communication devices
Medical and Scientific Instruments
Kovar is used in:
- MRI components
- X-ray tubes
- Laboratory equipment requiring glass-metal seals
- Cryogenic applications
## Fabrication and Machining Considerations
While Kovar can be machined using conventional methods, its work hardening tendency requires specific approaches:
- Use sharp tools with positive rake angles
- Maintain adequate cutting speeds
- Employ proper cooling techniques
- Annealing may be required between forming operations
The alloy can be welded using TIG or resistance welding methods, though care must be taken to minimize thermal stress.
## Advantages and Limitations
Advantages
- Excellent thermal expansion match with
