Nickel-based superalloys typically contain nickel and chromium as base elements and they can also contain molybdenum, tungsten, cobalt, niobium, aluminum, titanium and other elements. Nickel-based superalloys are good candidates for use in high-temperature applications because they possess properties that allow them to withstand temperatures up to 1400°C, and in some cases even higher.
The primary interactions in nickel-based superalloys are the nickel-rich gamma prime (γ′) phase and the chromium-rich gamma double prime (γ″) phase. The γ′ phase provides strength and creep resistance at high temperatures, while the γ″ phase provides oxidation resistance. These two phases interact through a precipitation hardening mechanism, which increases the yield strength at high temperatures, as well as a number of other beneficial effects.
The γ′ and γ″ phases also provide a form of deformation resistance called work hardening, which increases the yield strength at elevated temperatures. Therefore, when a nickel-based superalloy is deformed at high temperatures, it becomes harder, more ductile and more resistant to further deformation than it was before it was deformed. This is why nickel-based superalloys are often referred to as “work-hardening alloys”.
The high temperature properties of these alloys are due to their high solute content, which provides them with excellent creep resistance, high temperature strength and oxidation resistance. Other advantageous properties of these alloys are their resistance to fatigue, thermal fatigue and oxidation, as well as their ability to maintain their strength at high temperatures.
Nickel-based superalloys are used in a wide range of applications, from aerospace components, to turbine blades and even electronic packages. Their use is often limited by their cost, as they are typically more expensive than other alloy systems. However, their cost is often offset by their ability to provide excellent performance levels in high temperature applications, allowing them to be used in places where cheaper alloys would not be able to provide the required level of performance.
Nickel-based superalloys are also good candidates for use in structural applications due to their ability to maintain their strength under a wide range of loading conditions. They are also used in some applications where fatigue strength is an important factor, as the work hardening effects of their γ′ and γ″ phases can help increase their fatigue life.
Nickel-based superalloys have been used in high-temperature applications for many years, and have proven to be very reliable and effective materials for use in these applications. Their combination of strength, creep resistance, oxidation resistance, and work hardening ability make them ideal for use in a wide range of high temperature applications, from aerospace components to electronic packages.
