materials

Invar

Invar is an iron-nickel superalloy with an extremely low coefficient of thermal expansion, making it dimensionally stable even in environments with extreme temperature variation.

7.0

Relative Cost of Material

6.0

Machining Degree of Difficulty

Summary

Invar, similar to Kovar, is a superalloy generally chosen for its specialized CTE properties. Invar is a iron-nickel alloy with an extremely low CTE, hence the name ‘Invar’, which is short for ‘Invariable’ since the changes in dimension in different heat environments is minimal. Unlike Kovar, which has a CTE that closely matches that of borosilicate, Invar is commonly paired with lower CTE materials, including Zerodur, ULE, Fused Silica, Sapphire, Alumina, and many more. 

As these CTE properties have made Invar an increasingly common choice in both the aerospace and defense industries, Mindrum Precision has been machining tight-toleranced components for a variety of applications for decades. Click here for our contact information or to request a quote, and we will show you why more engineers are trusting us with their mission-critical needs.

Applications

Invar is frequently used in applications where a CTE match to a bonded or contacted material is key, and is a frequent choice for optics housings, window enclosures, and many other glass-adjacent applications, especially in aerospace and military applications. Similarly, having good thermal stability at low temperatures makes it a frequent choice for components dealing with liquid gasses or complementary components for delicate ceramic components in space applications as well.

 

Properties

Material PropertyInvar
Density (g/cm^3)8.4
Hardness (Rockwell B)68
Tensile Strength (MPa)500
Modulus of Elasticity (GPa)140
Poisson's Ratio0.29
Coefficient of Thermal Expansion (1 x 10^-6/°C)0.6 - 2.1
Thermal Conductivity (W/m K)12
Specific Heat (J/kg*K)505
*Note: Properties vary by manufacturer. The above information should be used for general reference purposes only.

related Materials

  • Kovar – An iron-nickel-cobalt alloy that is a close CTE match to borosilicate
  • Molybdenum – A high-density, low CTE refractory metal
  • A286 – A high-temperature, high-strength superalloy