Kovar is an Iron-Nickel-Cobalt alloy, best known for having a similar coefficient of thermal expansion (CTE) to Borosilicate glass and other optical materials that allows for glass-to-metal bonds.


Relative Cost of Material


Machining Degree of Difficulty


Kovar is a specialty alloy with CTE characteristics similar to multiple glass and ceramic components, that can be tailored to have specific non-linear thermal expansion curve to match the material it is mating with. This characteristic, along with good mechanical properties, makes it a frequent choice for temperature-sensitive glass and metal applications. In addition to having a similar coefficient of thermal expansion to borosilicate glass, Kovar is also a good CTE match for many other materials, including Aluminum Nitride, Shapal, Germanium, and Sapphire. It is significantly less expensive and easier to machine than Molybdenum, and can be used in extremely tight tolerances and geometries to manufacture advanced technical products.

As a specialty metal, Mindrum Precision manufactures parts out of Kovar on a near-constant basis. Our facility with this material allows us to deliver superior quality and pricing to our customers when they have needs in Kovar, as it can be challenging to machine if the proper strategies are not applied. 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.


While Kovar is chosen as a material almost exclusively for its thermal properties, there are no shortage of applications where that is the most important requirement. Kovar is present in everything from satellite propulsion systems and Mars rovers to light bulbs and cathode tubes, with new applications being found on a frequent basis.


Material PropertyKovar
Density (g/cm^3)8.35
Hardness (Rockwell B)68
Tensile Strength (MPa)517
Modulus of Elasticity (GPa)138
Poisson's Ratio0.317
Coefficient of Thermal Expansion (1 x 10^-6/°C)4.9 - 6.2
Thermal Conductivity (W/m K)17
Specific Heat (J/kg*K)460
*Note: Properties vary by manufacturer. The above information should be used for general reference purposes only.

related Materials

  • Invar – A Nickel-Iron alloy that is also designed to have a specific CTE
  • Molybdenum – A refractory metal with excellent thermal properties
  • Borosilicate – A family of glass materials that have CTE values comparable to Kovar components