Making the grade

News and developments in the world of corrosion resistant alloys through the eyes of Corrotherm International

INCONEL alloy 718: Properties and Applications

13 May 2021

INCONEL alloy 718: Properties and Applications
If you’re looking for a material that can retain high strength over a vast temperature range, consider INCONEL alloy 718. We take a closer look at its key characteristics

INCONEL alloy 718 is one of the many nickel-based superalloys supplied by Corotherm. Its exceptional properties and technical specifications mean that it’s used for lots of highly technical and essential industrial applications.

It is mostly chosen by design engineers thanks to its high strength in extreme temperature conditions at both ends of the spectrum. It can be used in environments from cryogenic all the way up to 1300°F/704°C. Throughout this entire range it exhibits exceptionally high yield, tensile and creep-rupture properties. It also shows excellent tensile and impact strength.

The alloy is made up of 50-55% nickel+cobalt (with cobalt limited to 1% max) and 17-21% chromium. This combination gives the material its corrosion-resistance properties. This includes good resistance to oxidation, enabling it to withstand corrosive media present in many of its applications.

The remainder of the composition includes niobium+tantalum (4.75-5.5%), molybdenum (2.8-3.3%) and titanium (0.65-1.15%), plus other balancing elements. It’s a potent and well-balanced combination of elements, responsible for the superalloy’s desirable technical properties.

Retaining strength

The material is age-hardenable with no significant detrimental effects. It responds slowly to being treated in this way, meaning that it can be annealed and welded without any spontaneous hardening during either heating or cooling.

Its room temperature strength is significantly improved by precipitation heat treatment, enabling it to withstand such extreme environments. Different heat treatment solutions are required, depending on the end use of the material – the method is different for either getting the best tensile and stress-rupture properties for high-temperature applications, or for maximising the benefits for use at room or cryogenic temperatures.

One of the outstanding features of INCONEL alloy 718 is that it is extremely versatile and easy to work with. It shows excellent welding characteristics, especially with regards to its resistance to post-weld cracking. In comparison to other nickel-based superalloys, particularly those hardened by aluminium or titanium, it is vastly superior.

Because it can be fabricated so readily and into increasingly complex parts, the material lends itself to high-performance applications.

Applications

INCONEL alloy 718 is often used within the aviation and aerospace industries. Engineers are constantly looking to improve the reliability and efficiency of engines, not to mention their longevity. Superalloys, and in particular alloy 718, are selected for their balance between cost and performance.

It’s imperative to use materials that can retain their strength and resistance to corrosion in the hottest sections of these engines. The materials used are under challenging conditions, with both mechanical and atmospheric stresses to consider.

INCONEL alloy 718 is ideal for use in these circumstances. For example, it has been used in jet engine and high-speed airframe parts, including wheels, fasteners, instrumentation parts, bolts, spacers and buckets. It is also used to engineer components for liquid-fuelled rockets, rings and casings, as well as various formed sheet metal parts for turbine engines, both aircraft and land-based.

At the other end of the temperature scale, INCONEL alloy 718 is also used in cryogenic tankage.

If you’re considering using INCONEL alloy 718 in your next project, Make An Enquiry today to find out more.

Published in Corrotherm News