Controlled Expansion Alloys – Alloy 42, 46, 48, 52, Kovar®, ASTM F15, Invar®, Super Invar 32-5

Ed Fagan is a leading supplier of controlled expansion alloys since 1965. The alloys classified in this category are Alloy 42, Alloy 46, Alloy 48 and Alloy 52, as well as Kovar®, Invar® and Super Invar.  These alloys are found in a broad variety of applications where thermal changes of a metal must be factored into the design of a component.  Typically useful when forming a hermetic seal with glass or ceramic or when a specific expansion must be met over a certain temperature range. Contact the Ed Fagan sales team to discuss your material needs and how our product line of controlled expansion alloys can fit your requirements.

Alloy 42

A controlled expansion alloy consisting of 41% nominal nickel, balance iron.  Used in a wide variety of electronic applications, lead frames, especially for glass and ceramic seals.  This alloy is also known as Pernifer® 42, NILO® 42, Carpenter Glass Sealing® 42.

Alloy 46

A nickel-iron controlled expansion alloy used in a wide variety of applications that require glass and ceramic seals.  Alloy 46 chemistry contains 46% nickel with the balance iron.  This alloy is also known by their manufacturer’s trade name of Pernifer® 46 and Carpenter Glass Sealing® 46.

Alloy 48

A controlled expansion alloy consisting of approximately 48% nickel and the balance iron.  This binary nickel-iron alloy is applicable to a wide variety of electronic applications that require a low coefficient of expansion at 400°C for glass-to-metal seals in soft lead or soda lime glasses.  Alloy 48 is also referenced under the manufacturer’s trademark names of Pernifer® 48 and NILO® 48.

Alloy 52

A controlled expansion alloy consisting of 50.5% nominal nickel, balance iron; used in a wide variety of electronic applications especially for glass seals.  This alloy is also known as Pernifer® 50 and Carpenter Glass Sealing® 52.


A low expansion alloy consisting of nominal 36% nickel; balance iron.  This controlled expansion alloy is known for its rate of thermal expansion that is approximately one-tenth of carbon steel at ambient temperatures up to 400°F.  These characteristics have made this alloy a contender for many applications where dimensional changes due to temperature variations must be minimized.  Invar is also known under these registered trademarks;  Invar 36®, Pernifer® 36, NILO® 36.

Invar Free-Cut “36”

Free-cut Invar “36” Alloy is a free machining nickel-iron alloy developed and produced by Carpenter® Technology.  This alloy variation provides a slight increase in thermal expansion properties when compared to Invar.  The addition of selenium to the chemistry delivers improved machinability for applications where high part productivity and good surface finish is important.

Kovar® | ASTM F15

Kovar® ASTM F15 is a vacuum melted, iron-nickel, low expansion alloy consisting of 29% nickel, 17% cobalt and balance iron.  Kovar’s coefficient of thermal expansion characteristics match both borosilicate (Pyrex®) glasses and alumina ceramics making this alloy a desirable choice for sealing metal to glass parts.  It is one of the most popular of the controlled expansion alloys for hermetic sealing and is also known as Pernifer®2918, Dilver®P1, NILO®K

Super Invar 32-5

An austenitic, magnetic iron-nickel-cobalt alloy consisting of 32% nominal nickel, 5% cobalt and the balance iron.  Super Invar 32-5 provides thermal expansion rates approximately less than half of Invar (36% nickel-iron) when used in the -67/203°F temperature range.  The slightly narrower application temperature range is due to a lower Curie temperature.


Ed Fagan supplies the highest quality controlled expansion special purpose alloys for the aerospace, aviation, communications, defense, electronics, energy, medical, nuclear, research and other high-technology industries.

CarTech® Glass-Sealing 42-6 Alloy, CarTech® Glass Sealing 46 Alloy, CarTech® Glass Sealing 52 Alloy, Invar 36®, Kovar® are registered trademarks of CRS Holdings LTD, Delaware.

Invar® is a registered trademark of Aperam Alloys Imphy, France.

NILO® 36, NILO®42, NILO® 48, NILO® K are registered trademarks of Huntington Alloys Corp, West Virginia.

Pernifer®36, Pernifer® 48, Pernifer® 50, Pernifer® 2918 are registered trademarks of VDM Metals GmbH, Germany