Alloy 718 is a high-strength nickel chromium superalloy that has excellent oxidation resistance and creep-rupture properties. It can be fabricated into complex parts, and it is very easy to weld, particularly in the annealed or precipitation-hardened condition. It also has very good corrosion resistance to many chemicals and acid solutions.
Inconel 718 is often used in power plants, chemical processing facilities and marine engineering, where it resists a variety of severely corrosive environments, pitting and crevice corrosion, and hydrogen embrittlement. It is also highly resistant to sulphide stress cracking, and it passes the NACE TM 0177 method C solution A test for sulphide stress cracking in hydrogen.
It is also highly resistant to erosion and abrasion in dry and wet conditions. This is especially true in the oxidizing environments found in petrochemical applications, where it demonstrates resistance to chloride and sulphur compounds at elevated temperatures.
The major components of inconel alloy 718 are nickel (52%), iron (20%), chromium (18%), cobalt + tantalum (10%) and molybdenum (3%). Small amounts of aluminum, titanium and tungsten are also present. In addition to its outstanding corrosion resistance, inconel has high tensile strength and excellent creep rupture properties, making it suitable for high-temperature bolts and fasteners. Its high modulus of elasticity also makes it more flexible than other nickel-based alloys, which can be beneficial when forming into long, continuous shapes. Inconel 718 can be machined with conventional methods, but it may require special tooling due to its rapid work hardening. In order to minimize the effects of work hardening, it is best to machine it while it is in the annealed or solutionized (precipitation-hardened) condition.