Cobalt alloys are resistant to wear, heat, and corrosion. This makes castings made of cobalt-based alloys valuable in various industries, including medical, aerospace, automotive, military, and other applications where high strength is essential and oxidation is an issue.
Cobalt Alloys: What You Need to Know
What is Cobalt?
A passivating oxide naturally covers and guards the strong, glossy, silver-gray metal cobalt against oxidation, which causes rust. Similar to nickel, only chemically mixed forms of cobalt (natural alloys) can be found in nature. However, reductive smelting can be used to create pure cobalt.
What Are Some Uses for Cobalt Alloys?
Orthopedic implants that do not degrade over time are made using cobalt-based investment castings. Due to their strength and lubricity, cobalt alloys are used in high friction bearing settings or products with an anti-galling quality. Moreover, this type of alloy displays good edge and thermal fatigue resistance in high-temperature settings like turbocharger turbines and jet aircraft turbines.
Cobalt-Based Investment Castings
There are many cobalt alloys, each with special qualities and advantages. The following are the most popular air-melted cobalt alloys:
- AMS 5382 / Cobalt Alloy 31 – This type is often characterized as having high tensile quality. It is extremely durable in metal-on-metal applications and can operate effectively at high temperatures.
- AMS 5385 / Cobalt Alloy 21 – AMS 5385 possesses reduced ductility and has exceptional thermal and mechanical shock resistance.
- KA3 cobalt alloy – It is resistant to abrasion and erosion due to its high carbon content.
- AMS 5387 / Cobalt Alloy 6 – This type of alloy is the most frequently employed because it works well in general wear scenarios. It also has high chemical resistance at a variety of temperature ranges. Likewise, it can maintain its hardness up to 900°F and resist surface pitting and impacts.
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