Kovar® – ASTM F15 Alloy

Pernifer® 2918, Dilver® P1, Nilo® K

Kovar® (UNS K94610) ASTM F15 Alloy

Ed Fagan Inc. is a leading global supplier of the nickel-iron-cobalt alloy, Kovar® Alloy (ASTM F15). This is a unique controlled expansion alloy with a combination of 29% nickel, 17% cobalt and the balance iron. Developed in the 1930’s, under the guidance of Westinghouse it was the first stress-free, glass-to-metal seal capable of maintaining its integrity in a range of environments. Today it is still the preferred alloy for hermetic sealing.


Product expansion characteristics match both borosilicate (Pyrex®) glasses and alumina ceramics making it one of the most popular of the controlled expansion alloys for hermetic sealing applications. A porosity free product, it is produced to ensure good properties for machining and deep drawing.


In manufacturing ASTM F15 Alloy, controls are exercised at various stages to assure close limits of thermal expansion and other desired properties are met. Procedural tests are conducted to measure uniformity and high-quality thermal expansion, transformation, cupping for “drawability”, Rockwell hardness, grain size, free from gas and glass sealing. Rod and wire soundness are assured by subjecting the primary bar stock to ultrasonic testing and microscopic examination of the ends. Thorough inspection of sheets guard against surface defects.


Kovar® or ASTM F15 Alloy is made not to undergo phase transformation from gamma to alpha at temperatures above minus 80 °C (minus 176 °F). Actual transformation is considerably lower. Where extremely low temperatures are service requirements, special selected alloy melts with specific transformation points can be supplied. Kovar® ( ASTM F15) is a stock material from Ed Fagan Inc. and has been tested by our mills to not transform to -196°C.


For over fifty years, Ed Fagan Inc. has been a leading supplier of Kovar® and controlled expansion alloys. With warehouses in NJ and CA, our stock of coil, strip, plate, round bar/rod and sheet is available in numerous sizes, tempers and conditions to meet the global demands of customers. All standard stock items are ready-to-ship for those in immediate need of materials.


Various manufacturers have produced ASTM F15 under their own brand names. Perhaps, these names are familiar to you, Kovar®, Pernifer® 2918, Dilver® P1 and NILO® K.

Ed Fagan Inc. is a leading supplier of Kovar® – ASTM F15 Alloy. A controlled expansion, glass-to-metal sealing alloy that is also known as Pernifer® 2918, Dilver® P1, Nilo® K.

Dilver is a registered trademark of Aperam Alloys Imphy, France

Kovar is a registered trademark of CRS Holdings LTD., Delaware, USA

NILO is a registered trademark of Huntington Alloys Corp., West Virginia, USA.

Pernifer is a registered trademark of VDM Metals GmbH, Germany