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Kovar Material Suppliers

Kovar is a nickel-iron-cobalt, controlled expansion alloy. It's expansion characteristics match both borosilicate (or Pyrex) glasses and alumina ceramics. This alone ensures it is a highly popular controlled expansion alloys for hermetic sealing applications (also known as Glass to Metals Sealing). 

City Special Metals manufacture a variety of Kovar Alloy Products, including Kovar Plates, Bars and Saws. As well as Kovar, we are also widely known as Europe's largest stockist of low and controlled expansion alloys. Discuss your requirements by contacting our team today.

Kovar Stockist Range

Product FormRange FromRange To
Kovar Plate iconKovar Plate4mm210mm
Kovar Round Bar iconKovar Round Bar4mm160mm
Kovar Sheet & Coil iconKovar Sheet & Coil0.025mm3.175mm
Kovar Wire iconKovar Wire0.1mm3.175mm
Kovar Tube iconKovar Tube3.175x0.254mm25.4x1.0mm

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Kovar Alloy Products & Properties

City Special Metals stock and supply a wide range of kovar products and materials. Therefore, it should be no surprise that we know a lot about Alloy K too.

Head over to our insights pages if you’d like ro read more about Kovar. We’ve written features about the Machinability of Kovar®, plus much more.

Ready to enquire with City Special Metals? We’re a leading UK based speciality metals stockist and always happy to help. Skip to our contact form below, fill in some details and also tell us about your Kovar Material Requirements requirements. Click here to skip down the page. 

Alternatively, below is information on the Applications, Products and Properties of this versatile controlled expansion alloy.

Beneficial Properties

  • Expansion Control Reliable hermetic sealing applications
  • Uniformity Precise and uniform thermal expansion characteristics
  • Shock-resistant Their coefficient thermal expansion makes the seal resistant to shock and cracking

Markets & Applications

  • Hermetic sealing
  • Production of transistors and diodes in electronic industry
  • Vacuum systems in chemistry and scientific research
  • Electronic tubes (power, X-Ray)
  • Hybrid circuit casings
  • Oscillator housings
  • Concentrated solar power
  • Scientific instruments

Kovar Mechanical Properties

Metallurgical ConditionAnnealed, Descaled
Yield StrengthKSI (MPa)40 (276)
Tensile StrengthKSI (MPa)75 (518)

Kovar Technical Specifications

F15K946101.3981I-23011 CL1

Kovar Chemistry


Kovar Physical Properties

Co Efficient of Thermal Expansion
20-100°C10-6/°C0.8 - 1.7
20-200°C10-6/°C2.2 – 2.9
Curie Temp°F815
Melting Point°F2640
Modulus of Elasticity at 20°CMPa207
Specific HeatJ/g- °C0.11
Thermal Conductivity at 20°CW/m.k17.3
Thermal ExpansionW.m-¹°C0.17
Electrical Resistivitymm²/m49
Poisson's coefficient0.317

We offer a bespoke service so, if you don’t see the size or form that you require, contact us either by phone, email or our contact form below, and we will provide a solution to your requirements.

A Versatile Controlled Expansion Alloy

Kovar has been in use for many decades as a controlled expansion alloy. However, despite its relatively long history, many people outside the engineering industry have never heard of Kovar.

What makes Kovar so unique is it's coefficient of thermal expansion. As a controlled expansion alloy, it shared some remarkable similarities to borosilicate glass (hard glass) and ceramic.

Kovar's coefficient of thermal expansion is not an accident, though. Going back in history, Kovar was carefully formulated to meet a specific need. In 2019 and beyond, City Special Metals serve to manufacture Kovar to the highest standard. You can learn more about our Quality Assurances here.

Kovar is also known by the following trade names

  • Kovar®
  • Pernifer 29-18®
  • Dilaton 29-18® Dilver P®
  • Dilver® NiCoFe®
  • Telcoseal 1®
  • Sealvar®
  • Nilo K®
  • Nicoseal®
  • Nicosel®
  • Therlo®
  • FeNi29Co17®