If you’ve ever asked yourself “What is a superalloy?”, you’re in the right place. Superalloys are a class of metal alloys whose properties for strength, corrosion resistance, and ability to resist mechanical deformation under stress for extended periods of time far exceed those of other metals like steel, stainless steel, and aluminum that are in common use. The specific qualifier for a superalloy is that it retains its operational properties under a high fraction of its melting point. That definition is vague for everyday use so the common—if unofficial—working definition of a superalloy is a metal that doesn’t begin to lose its strength until it exceeds 1,000°F or around 540°C.

Overwhelmingly, superalloys are nickel, nickel-iron, or cobalt alloys that don’t begin to experience a loss of strength or surface softening until around 1,100°F (~600°C). Their value in large part comes from this ability to provide strength under high heat and pressure, and these alloys have been what has enabled very high temperature engineering projects.

The most commonly known example are the turbines that make jet engines, but they also enable the manufacture of a variety of exotic plastics, ceramics, and ceramic metals that can make lighter but still heat resistant jet engine parts, and also—surprisingly—dental implants and crowns and much more besides.

Why do Superalloys Matter?

The reason that superalloys matter is their extreme resistance to heat. This opens up a range of options that simply wouldn’t be possible if these alloys didn’t exist. Either they wouldn’t be possible in the first place due to the extremes of heat required or the maintenance requirements to keep processing equipment operating under these extremes would be so high as to make them too costly.

Jet engines for example, are possible to build without superalloys. Without superalloy’s ability to resist heat for extended periods of time, flight distances would be circumscribed to the point that transoceanic flights would require stops midway to avoid damaging the engine.

This sort of issue would apply to many of the following industrial applications:

• Turbocharging rotors used in performance cars, and diesel engines
• Heat exchangers used in chemical processing and power generation
• Nuclear reactor vessels and the steam generators that transfer thermal energy
• Turbine shafts, blades, and vanes in both thermal and nuclear power plants

There are a wide range of applications that we take for granted every day that, if not enabled by superalloys’ ability to resist heat, are made much more reliable.This heat resistance is only one of the extraordinary properties of this class of metals too. They also have extraordinary resistance to corrosion which is driving a greater demand for them in marine applications, the petrochemical industry, chemical manufacturing, and even for medical devices like implants and stents. Although, medical devices are not typically the same formulations as the superalloys used in heavy industry. The drawbacks to these metals that counterbalances the benefits of unique properties though is that they are very expensive, and they are difficult to work with.

New Superalloys Compared to Remnants

Nickel, nickel-iron, and copper-nickel superalloys like Inconel, Hastelloy, and Monel are very pricey. The expense of these metals is significant enough that welding parameters for lining stainless or mild steels with a layer of Inconel, Hastelloy, or Monel are well developed and common practice. They are often more well developed than metal cutting methods for super alloys are. In other words it’s often more economical to pay a skilled laborer to spend hours lining a piece of mild steel with welded beads of superalloy than it is to just buy a plate of superalloy outright. Typically, superalloys are only really economical to use when literally nothing else will meet the requirements. This somewhat limits the use of what are for all intents and purposes a wonder material.

A potential exception to the incredible expense of these metals may be the use of verified remnants. These are pieces that are left over after other industrial processes take what they need from standardized sized plates or bar stock. They are, for all intents and purposes, the same as new metal but come in non-standard sizes. The only real difference is that the typical certifications cannot be applied, so remnant metals aren’t suitable for applications in heavily regulated industries like aerospace.

On the other hand, a custom superalloy drive shaft can deal with the high torque from an electric motor in a prototype piece of equipment or electric vehicle, and a custom machined manifold for corrosive fluids or gas can also be an incredible benefit.

The use of remnant Inconel, Hastelloy, and Monel in applications where normally the costs would be far too much open up many potential benefits. Given that these materials have opened up incredible new options just by existing the potential of being able to obtain and use them in applications where they normally wouldn’t be used is hard to overstate.