Types of Superalloys
Introduction
Modern production standards are extremely demanding. Engineers and designers are constantly asked to meet industry requirements for performance, longevity, sustainability and cost optimization. Industrial production is in a state of constant development. New design principles, production methods and materials are essential for innovation.
Some industries are particularly demanding, such as the aerospace industry. Aerospace products are subject to extreme conditions during their service life. Traditional methods and materials are not enough to meet industry standards: this is why aerospace engineers use materials such as superalloys.
What are superalloys?
Essentially, superalloys are materials with extreme performance statistics. The key properties of superalloys are high durability, extreme mechanical strength, thermoelasticity and long life. The most important property of a superalloy is its ability to operate at high fractions of the melting point. All of the above properties make superalloys essential to the aerospace industry.
The original idea to develop materials suitable for operating in extreme conditions came from the desire to design vehicles that could take us higher and faster. The development of superalloys is closely linked to the rapid expansion of the aerospace industry after World War II.
Types of superalloys
There are many types of superalloys used in the aerospace industry. One of the most commonly used types is titanium-based superalloys. Pure titanium has a relatively low density, high strength, and high corrosion resistance. In addition, titanium is the only element that burns with nitrogen. Titanium is as strong as steel, but weighs almost half as much. These properties alone make it an ideal material for the aerospace industry, where the weight/strength ratio is critical. Titanium is mixed with other elements in specific proportions to further enhance its already excellent properties.
One of the most commonly used titanium-based alloys is the Ti-6Al-4V alloy. It contains aluminum and vanadium in addition to titanium and is primarily used in cockpit frames, wing boxes, and fastener structures for commercial aircraft. This alloy exhibits a good balance of properties such as strength, ductility, fracture toughness, high temperature strength, creep properties, weldability, machinability, and hot workability. Ti-6Al-2Sn-4Zr-2Mo alloy is a heat-resistant alloy developed in the late 1960s. Its heat resistance temperature is about 450˚C. This alloy is often used in compressor disks, and its upper service temperature is 500˚C. Ti-5Al-2Sn-2Zr-4Cr-4Mo alloy, sometimes referred to as "Ti17" alloy, is an alloy with high strength and excellent fracture toughness developed in the United States in the 1970s. Its heat resistance temperature is about 350˚C. In commercial aircraft engines, the fan and shaft are constructed as one piece to reduce the weight of the engine. Ti-10V-2Fe-3Al alloy has excellent hardenability, high strength and high fatigue strength and is mainly used in landing gear.
In addition to titanium-based alloys, iron-based alloys are another class of alloys that are commonly used in various industries such as aerospace and military industries. Essentially, iron-based alloys are alloys that are mainly composed of iron. Some of the most commonly used iron-based alloys are stainless steel, cast iron, and high carbon steel. Iron-based alloys generally exhibit a good balance of properties, including heat resistance, corrosion resistance, durability, strength, and thermal elasticity. Although they do not exhibit extremely high performance like titanium-based high-temperature alloys or other high-temperature alloys, their ease of synthesis and cost-effectiveness make them invaluable.
Another important alloy category in the aerospace and military industries is aluminum alloys. The weight-to-strength ratio of raw aluminum is already impressive in itself. Adding the alloying elements copper, magnesium, manganese, silicon, tin, nickel, and zinc enhances these properties, making aluminum alloys ideal for military and aerospace applications. The 7xxx series of aluminum alloys is the most commonly used category in aerospace applications. The primary alloying element in the 7xxx series is zinc, making this category the strongest aluminum alloy. The yield strength of the 7xxx series alloys exceeds 500 MPa. The most common 7xxx alloys are Al-Zn-Mg-Cu and Al-Li-Cu-Mg.
