Kovar® Metal-Alloy Supplier

About Kovar® Metal and Kovar® Alloys

Kovar® is an alloy made up of 29% nickel, 17% cobalt, .2% silicon, .3% manganese and 53.5% iron. Kovar® is known for its low coefficient of thermal expansion. Kovar is suitable for uses which require a matched expansion seal between metal and glass parts.  Kovar® end uses are usually glass sealing in the electronics industry.

Kovar not only has thermal expansion similar to glass, but its nonlinear thermal expansion curve can often be made to match a glass, thus allowing the joint to tolerate a wide temperature range. Chemically, it bonds to glass via the intermediate oxide layer of nickel(II) oxide and cobalt(II) oxide; the proportion of iron oxide is low due to its reduction with cobalt. The bond strength is highly dependent on the oxide layer thickness and character. The presence of cobalt makes the oxide layer easier to melt and dissolve in the molten glass. A grey, grey-blue or grey-brown color indicates a good seal. A metallic color indicates lack of oxide, while black color indicates overly oxidized metal, in both cases leading to a weak joint.

*Kovar is a registered trademark of CRS Holdings, Inc., a subsidiary of Carpenter Technology Corp.
*Pernifer 2918 is a registered trademark of ThyseenKrupp-VDM, Germany 
*Dilvar P1 is a registered trademark of Imphy Alloys, France 
*NILO K is a registered trademark of Special Metals Corporation, USA

*Above data is for informational purposes only. Eagle Alloys is not liable for accuracy of these contents or applications. Finished part drawings may be forwarded to a third party for outsourcing.