Views:71 Author:Ronsco Publish Time: 2020-05-11 Origin:Nickel Alloy Knwoledge
What is INCONEL® alloy 718 (UNS N07718/W.Nr. 2.4668)?
INCONEL® alloy 718 (UNS N07718/W.Nr. 2.4668) is a
high-strength, corrosion-resistant nickel chromium
material used at -423° to 1300°F. Typical composition
limits are shown in Table 1.
The age-hardenable alloy can be readily fabricated,
even into complex parts. Its welding characteristics,
especially its resistance to postweld cracking, are
The ease and economy with which INCONEL alloy 718
can be fabricated, combined with good tensile, fatigue,
creep, and rupture strength, have resulted in its use in a
wide range of applications. Examples of these are
components for liquid fueled rockets, rings, casings and
various formed sheet metal parts for aircraft and land-based
gas turbine engines, and cryogenic tankage. It is also used
for fasteners and instrumentation parts.
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.
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.
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.