Alloy 718, UNS N07718
Alloy 718 is an age-hardenable austenitic material. Strength is largely dependent on the precipit prime phase during heat treatment.
Good fabricability in the annealed condition;
Good tensile, fatigue and creep-rupture strengths; at up to 700℃;
High-temperature strength up to 700℃;
Good oxidation resistance up to 1000℃;
Excellent mechanical properties in cryogenic environments;
Good weldability by arc and without susceptibility to post-weld cracking.
Alloy 718 has excellent corrosion resistance to many media. This resistance, which is similar to that of other nickel-chromium alloys, is a function of its composition. Nickel contributes to corrosion resistance in many inorganic and organic, other than strongly oxidizing, compounds throughout wide ranges of acidity and alkalinity. It also is useful in combating chloride-ion stress-corrosion cracking. Chromium imparts an ability to withstand attack by oxidizing media and sulfur compounds. Molybdenum is known to contribute to resistance to pitting in many media.
Due to its high-temperature strength up to 700℃, excellent corrosion resistance and ease of fabrication Inconel 718 finds applications in many field. Initially it was used as a turbine disk material in aircraft jet engines. Here resistance to creep and stress rupture eas most important. Because of its properties, fabricability and cost effectiveness it has since gained wider acceptance. Today applications vary from highly stressed rotating and static components in gas turbines and rocket engines to high-strength bolting, spring and fasteners, components in nuclear reactors and space vehicles as well as high-temperature tooling for extrusion, of for example copper, and shearing. Another more recent important application involves pump shafts and other highly stressed well head and downhole components in offshore Particularly useful is the alloy for drilling equipment in sour (containing H2S, CO2 and chlorides) oil and gas wells.