Inconel® 718 (UNS N07718, DIN 2.4375) is a widely used nickel-based alloy, with significant alloying additions. As a nickel-based alloy it is effectively non-magnetic. Although it may contain up to 20% iron by weight, most people would consider it to be non-ferrous and describe it as a super alloy on account of its properties at elevated temperatures.
Inconel 718 was originally developed for use in steam power plants, but became more widely used in aerospace applications on account of its resistance to oxidation at elevated temperatures. However, its ready availability, combined with high strength and excellent corrosion resistance in seawater made it a suitable candidate for emerging applications in the oil and gas industry.
Inconel 718 retains much of its mechanical properties up to 650degC (1200degF), although it will resist oxidation at far higher temperatures. The melting point of Inconel 718 is in the range 1260-1340degC (2300-2440degF).
Nickel-based alloys such as Inconel 718 will work harden during machining, drilling and fabrication. Given that it is already a high-strength alloy when supplied in the aged condition, careful selection of tooling, coolant and CNC machine settings is required. Inconel 718 can be readily welded, usually with a matched filler metal if being welded to itself.
Comparing Inconel 718 vs. Inconel 625, then Inconel 625 has a higher alloy content and therefore improved corrosion resistance in most environments, albeit at a greater cost. However, Inconel 718 has higher strength, due to a combination of alloying additions and heat treatment that allow it to age harden.
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