Why is INCONEL 718 called a super alloy?
Inconel 718 (or Alloy 718) is a special type of high-strength, high-temperature alloy with a nickel-chromium base that resists corrosion, high pressures and extreme temperatures up to 700 degree .
The material is composed of 50-55% nickel, 17-21% chromium, 4.75-5.5% niobium and tantalum, and trace amounts of molybdenum, titanium, cobalt, aluminum, manganese, copper, silicon and other elements.
Due to its unique properties, Inconel 718 has been used in a wide range of applications ranging from manufacturing operations to military equipment and the aerospace industry.
Features of Inconel 718
Inconel 718 has a melting point of 1430 degree and provides effective heat and high temperature resistance. It also works well at low temperatures, which shows the range of temperature resistance the material has.
At room temperature, superalloy materials have a minimum yield strength of 725 MPa and a minimum tensile strength of 1035 MPa. When Inconel 718 is solutionized and precipitated, these figures increase to 1035 MPa and 1240 MPa respectively.
Other Inconel alloys are difficult to weld due to brittleness and cracking at precise weld points. However, Inconel 718 was created to solve this problem, whether using electron beam or arc welding.
Most Inconel alloys tend to undergo strain hardening when attempted to be machined or formed. Inconel 718 is different - it is easier to machine using hard cutting tools through slower cutting mechanisms.
After the material is fully aged, this high-temperature alloy can be threaded by induction heating at 700 degree .
Inconel 718 can be produced by the following processes:
In annealing (also known as solid solution strengthening), the metallic components are completely dissolved so that they can properly precipitate, giving Inconel 718 the strength it was designed to deserve.
In precipitation strengthening, nickel and niobium combine to form gamma bis(or Ni3Nb). Extreme heat above 800 degree can cause precipitation of the nickel phase.
It follows that Inconel 718 can be machined into custom shapes and orientations when processed above 540 degree .
Applications of Inconel 718
3D printing
Inconel 718 has become associated with 3D printing technology as the alloy effectively prints parts across a variety of industries. Several studies have explored the use of superalloys in the additive manufacturing (AM) industry and their further enhancement to maximize their functionality.
Due to the material's strength and durability, Inconel 718 has become a popular component for turbojet engine parts such as compressor casings, discs, and fan blades. This high-temperature alloy is also used in the production of rocket engines, especially due to the alloy's high heat resistance. This is the main reason why Inconel 718 is used in approximately half of conventional aircraft engine parts.
This Inconel variant works well in hot environments, making it ideal for extreme high temperature applications such as metal die casting. Other nonferrous metals are more popular in the industry, but Inconel 718 is tough enough to protect itself from damage. As a result, molds or mold bases made of Inconel 718 have a longer service life and better resistance to deformation.
