Superalloys are high-performance metallic materials composed of at least two elements exploited for their temperature and chemical resistance, and high strength. Superalloys find many applications in harsh environments in industries including: medical, aerospace, and chemical processing. In these industries, superalloys are used as medical implants, turbine blades, and instruments. Superalloys are most commonly nickel-, iron-, or cobalt-based. The main advantages of using these materials are their heat resistance and strength properties.
There are five main types of superalloys: nickel, iron, cobalt, titanium, and niobium. Each superalloy is discussed below:
Nickel-Based Superalloys
Nickel-based superalloys most commonly consist of nickel and aluminum and/or titanium. These alloys are widely used as turbine blades in jet engines and turbochargers due to their desirable material properties at high temperatures. An example of a nickel-base superalloy is Inconel®. Inconel® is made of nickel and chromium which results in high levels of corrosion resistance at high temperatures.
Iron-Based Superalloys
Iron-based superalloys are formed of iron and nickel or chromium. Iron-based alloys are cheaper than other superalloys and are well-known for their wear resistance. Iron-based alloys are used in aircraft bearings and other applications which are subject to moving contact.
Cobalt-Based Superalloys
A cobalt superalloy contains 50–60% cobalt mixed with 20–30% chromium and 5–10% tungsten. Cobalt alloys have a high fatigue life and higher strength than iron- and nickel-based superalloys in high-temperature applications. Due to their high corrosion resistance, they form some of the parts of a gas turbine that are exposed to the atmosphere.
Titanium-Based Superalloys
Titanium-based superalloys use titanium mixed with roughly 11% molybdenum which reduces the elastic modulus of the superalloy. A titanium-based superalloy's unique property is its high hardness. Titanium-based superalloys find many applications in the aerospace and biomedical industry. One example of a titanium-based superalloy is Ti6AL4V which is a titanium-aluminum alloy.
Niobium-Based Superalloys
Niobium-based superalloys are often made of niobium and nickel. Niobium-based superalloys have relatively low strength when compared to other nickel-based base alloys. However, they retain their strength much better than nickel-based alloys at high temperatures. Niobium-based alloys have high usage in jet engines and rockets thanks to their high-temperature resistance.
