What is Kovar？

Kovar refers to a common iron-nickel-cobalt alloy (Fe-Ni-Co alloy). Its name "Kovar" comes from the combination of the surnames of its creators Kovacs and Vakoma. Because it has a thermal expansion coefficient similar to that of glass and ceramics, it is widely used in sealing, electronics and vacuum technology.

1. Basic composition of Kovar alloy

The main component of cobalt-based alloys is cobalt, and elements such as chromium, nickel, and iron are usually added. The specific composition varies according to different application requirements:

Cobalt (Co): It is the basic element of Kovar alloy, usually accounting for 50% to 60% of the alloy. Cobalt has excellent high temperature resistance, corrosion resistance and wear resistance.

Chromium (Cr): Commonly used to improve the corrosion resistance and wear resistance of alloys. Chromium can form a stable oxide film to enhance the oxidation resistance of the alloy.

Nickel (Ni): Improves the corrosion resistance and toughness of the alloy, while improving the alloy's crack resistance and low-temperature performance.

Iron (Fe): Small amounts of iron may be added to some cobalt-based alloys to reduce cost and enhance their resistance to oxidation and corrosion.

Carbon (C): The addition of carbon can increase the hardness and strength of the alloy, but too much carbon will make the alloy more brittle.

Molybdenum (Mo), tungsten (W), aluminum (Al), etc.: These elements are often used to enhance the high temperature resistance and oxidation resistance of alloys.

2. Physical properties

Density: Usually around 8.36 g/cm³.

Melting point: about 1450°C.

Coefficient of Thermal Expansion: Matched to borosilicate glass over the range of 20°C to 400°C, typically between 4.6×10⁻⁶/°C and 6×10⁻⁶/°C.

Conductivity: Moderate, not as good as metals like copper or silver.

3. Main characteristics of Kovar alloy

High temperature resistance: Kovar can still maintain good mechanical properties in high temperature environments and are not easily oxidized or deformed. Therefore, they are widely used in high temperature working environments, such as aircraft engines, gas turbines, etc.

Corrosion resistance: Kovar have excellent chemical corrosion resistance and can be used for a long time in acidic or alkaline environments. They are especially suitable for harsh environments such as chemical, petroleum, and marine.

Wear resistance:Kovar has high hardness and wear resistance, so it is widely used in the manufacture of mechanical parts, tools and other friction parts, and can withstand long-term wear.

Fatigue resistance: Under long-term pressure and repeated loads, Kovar can maintain good mechanical properties and have good fatigue resistance.

Biocompatibility:Kovar have good biocompatibility in the medical field and are widely used in biomedical fields such as artificial joints and dental materials.

4. Mechanical properties

Strength: High tensile strength and hardness to withstand mechanical stress.

Toughness: Has good toughness and ductility.

Machinability: Easy to turn, drill and mill, suitable for precision machining.

5. Heat treatment performance

Annealing: The ductility and mechanical properties of the harvestable material can be improved by proper annealing treatment.

Hardening: Can be hardened by cold working or heat treating.

6.Application areas:

（1）. Aerospace

Kovar are widely used in the aerospace industry, especially in environments with high temperature, high pressure and strong friction. The main applications include:

Aircraft engines: Key components such as turbine blades, combustion chambers, nozzles, gas turbines, etc. require materials to have extremely high heat resistance and oxidation resistance, and cobalt-based alloys meet this requirement.

Rocket engines and propulsion systems: In rocket engines, Kovar are important materials due to their high temperature resistance, corrosion resistance and strength. They are used to manufacture high-temperature components such as combustion chambers, nozzles, etc.

Thermal protection systems: Kovar can be used in thermal protection systems in high-temperature environments to protect spacecraft and satellites from high-temperature damage.

(2). Chemical Industry

Kovar are widely used in the chemical industry due to their corrosion resistance, especially those environments involving highly corrosive media:

Chemical reactors: Kovar are able to remain stable in strong acids, alkalis and other corrosive chemical media, and are therefore widely used in the linings, valves, pumps and pipes of chemical reactors.

Petrochemical equipment: In petrochemicals, Kovar are used for corrosion-resistant parts in the production process, such as catalyst reactors, storage tanks, pipelines, etc.

(3). Medical field

Kovar are widely used in the medical industry, especially in orthopedics and dentistry, due to their good biocompatibility, wear resistance and strength:

Artificial joints: Kovar are often used to manufacture artificial knee joints, hip joints, etc. because they have excellent wear resistance and mechanical properties when subjected to loads for a long time.

Dental Materials: Kovar are widely used in dental restorative materials, especially for crowns and bridges, due to their good biocompatibility and wear resistance.

Orthopedic implants: For example,Kovar are used to make bone screws, artificial bones, etc., because of their good biocompatibility and are not prone to allergic reactions.

(4). Automotive Industry

In the automotive industry, Kovar also have some applications due to their excellent wear resistance and high temperature resistance:

Engine parts: Some high-performance automobile engine parts, such as turbocharger blades, valve seats, etc., use Kovar materials to improve durability and high temperature resistance.

Braking system: The wear resistance of Kovar also makes them suitable for some high-end braking system components, such as brake discs and brake pads.

(5). Military

Kovar have extensive potential in military applications, especially in high-performance weapons, missiles and protective equipment:

Missile nozzles:Kovar are often used in key components such as missile nozzles due to their high temperature and corrosion resistance.

Military equipment: Kovar can be used to make high-strength, wear-resistant parts, such as protective plates for armored vehicles.

(6). Electronics and communications

Kovar are also used in certain demanding electronic devices, especially where high temperature stability is required:

High-frequency electronic components: Kovar are used in high-frequency electronic devices, such as high-frequency transformers, sensors, etc., because of their good thermal stability and electromagnetic shielding properties.