close up of a cobalt alloy investment cast part

Benefits of Cobalt Alloy Castings

Considered a universal alloy, cobalt is relied upon by manufacturers for its excellent mechanical properties and superior wear, oxidation, corrosion, impact, and shock resistance at elevated temperatures. cobalt alloys are also commonly used in the investment casting process.
Despite the many advantages of cobalt, there are several factors to consider before deciding to use it for your investment casting project. It is important to understand the chemical composition, mechanical properties, and how that material will react during the manufacturing process.
In this brief guide, we’ll cover the basic chemical composition of the Cobalt 6, Cobalt 21, and Cobalt 31 family of alloys compare it to other alloys on the market, and help you understand how, when, and why to use it for your casting application.

Chemical Composition

These cobalt-chromium alloys that contain some combination of carbon, tungsten, molybdenum, nickel, iron, manganese, and silicone. They generally have excellent wear, cavitation, abrasion, and corrosion resistance.

Cobalt 3 alloys are composed of cobalt, chromium, tungsten, nickel, iron, manganese, and silicon. Cobalt 6 contains lower amounts of cobalt, chromium, and tungsten compared to Cobalt 3, but also contains molybdenum, nickel, iron, silicon, and manganese. Cobalt 21 contains carbon, chromium, molybdenum, and cobalt, while Cobalt 31 contains higher amounts of carbon and lower amounts of chromium, tungsten, cobalt, and nickel.

While the chemical makeup of the many cobalt alloys varies from one to the next, the carbon and chromium content can be considered the elements that impact the alloys’ performance the most. High-carbon cobalt alloys have excellent wear resistance, while low-carbon alloys perform well in high-temperature applications. Finally, low-carbon and high-chromium alloys have excellent corrosion resistance.

Benefits of Cobalt

The primary benefit of cobalt-chromium alloys is their ability to maintain their superior mechanical properties, such as strength and high hardness, at elevated temperatures. As previously mentioned, these alloys are relied upon for their excellent wear, impact, corrosion, and erosion resistance. However, the same properties that make these alloys so valued are the same properties that decrease its machinability. Although the hardness value of cobalt makes it difficult to machine, it’s still one of the best alloys to use for investment casting. When using cobalt for investment casting, manufacturers are able to produce parts with tight tolerances, reducing the need for machining.

Advantages of Using Cobalt Over Stainless Steel

While cobalt alloys are more expensive than other metal alloys like stainless steel, they don’t require as many additional processing steps after casting. The cobalt matrix and complex microstructure within these alloys provide them with much better corrosion, wear, oxidation, and heat resistance than stainless steel or other metal alloys.

Lastly, cobalt alloys perform much better than stainless steel at high temperatures. Therefore, cobalt is not only a stronger and more durable material, but it also has superior corrosion, oxidation, and wear resistance than stainless steel at much higher temperatures.

Most Commonly Used Cobalt Alloy

The most common cobalt alloy used to produce castings is Cobalt 6. These cobalt-chromium and tungsten alloys have a Rockwell Hardness Value of 42 HRC and an operating temperature approaching 1,100 degrees Fahrenheit.

Cobalt 6 has fantastic wear and oxidation resistance, as well as a low coefficient of friction. Cobalt 6 castings also have excellent impact and shock resistance and don’t typically require additional heat treatments.

Cobalt 6 castings are most commonly used in the Aerospace and Oil/Gas industries. Petrochemical and refining processes use air, chamber, reactor, and stripping nozzles cast from Cobalt 6. Pumps, pump components, and valves are also cast from Cobalt 6.

Find Your Solution With Help From Barron Industries

Barron Industries is an ISO 9001 and AS 9100-accredited investment casting foundry. We have the ability to produce castings from over 200 ferrous and non-ferrous alloys, including Cobalt 3, 6, 21, and 31. To ensure quality, our state-of-the-art facility also includes a NADCAP-certified non-destructive testing lab for digital radiography and liquid penetrant testing. If you have general questions about cobalt alloys or want to learn more about our turnkey capabilities please contact us today.