1. Composition
Kovar alloy: generally contains about 29% nickel, 17% cobalt and 54% iron.
Invar alloy: generally contains about 36% nickel and 64% iron25.
2. Performance
Thermal expansion coefficient: The thermal expansion coefficient of Kovar alloy is 4.57x10⁻⁶m/mK, and the thermal expansion coefficient of Invar alloy is only 1.2x10⁻⁶m/mK4.
Melting point and density: The melting point of Kovar alloy is 1430°C and the density is 8800kg/m³; the melting point of Invar alloy is about 1425°C and the density is 8100kg/m³4.
Magnetic properties: Kovar alloy has strong magnetic response, Invar alloy is magnetically soft, with low coercivity and hysteresis.
3. Processing difficulty
Kovar Alloy: Good processing performance, can be easily formed by cold rolling, hot rolling, pressing and forging.
Invar alloy: Due to its high hardness and toughness, it is difficult to process.
4. Application fields
Kovar alloy: With a thermal expansion coefficient similar to that of hard glass, good thermal shock and chemical corrosion resistance, it is often used in electronic packaging, vacuum sealing equipment, airtight containers, transistors and other fields.
Invar alloy: With its extremely low thermal expansion coefficient, it is mainly used in occasions with extremely high requirements for dimensional stability, such as scientific instruments, precision optical equipment, high-precision parts in aerospace, etc.
