Working with nickel-based superalloys – here’s what you need to know

Working with a nickel-based superalloy can take skill and practice to perfect. Here are some tips and advice
Nickel-based superalloys combine high strength with exceptional corrosion resistance. These super properties make them a popular material of choice across numerous industries.
The INCONEL family of products has been specifically designed to handle the most extreme of environments. Now used in everything from chemical processing and aerospace, to the extraction and storage of oil and gas, INCONEL nickel alloys represent the premium standard in working metals.
All the different grades of INCONEL have high levels of nickel, with the flagship INCONEL alloy 625 containing a minimum of 58% nickel in its composition. When combined with significant levels of chromium, these nickel alloys offer better resistance to corrosion and high temperatures than other competing alloys.
Machining nickel superalloys
However, when choosing to work with one of these nickel-based superalloys, it’s important to know how to handle them. Such highly specialized and technical materials need to be worked and machined by an engineer who understands the unique properties of the INCONEL range. Nickel-based products can be hard to machine without the right approach and processes.
For a start, you’ll need to keep an eye on your machining speeds. Working with such a durable metal alloy at high speed using a solid carbide end mill will shorten your tool life and lead to work hardening. This means you need to be prepared to resharpen or change your tool regularly. However, you can use these high-speed drills at slower speeds if that’s the best option for your machines.
You may opt to work with cobalt drills, especially when using twist drill bits. If it’s feasible to do so, it’s also worth using C grade inserts, which are more expensive but can make machining these alloys easier. All of these tooling options make a difference to your manufacturing productivity, so play around with the combination that’s right for your business.
Another thing to consider when machining these high-spec nickel alloys is your use of coolants. Machining these nickel superalloys creates a lot of heat, which can warp the material as you work it. You may need to experiment with the right combination and quantity of coolants and lubricants, depending on the project. For example, for CNC machining, some engineers find using water-miscible vegetable oil-based fluids to be productive.
Welding and fillers for nickel superalloys
It’s also possible to weld nickel superalloys, but as with machining it takes a bit of practice, experience and knowledge. Because these high-nickel alloys are designed to withstand high temperatures, this can make it more difficult to weld the material and the welds can crack.
Picking the right filler material is important. Something like INCONEL alloy 625 is a good option for a filler to join two pieces of these superalloys together. If these welds are done with precision and skills, these welds should be both strong and highly corrosion resistant.
When it comes to welding methods, the most commonly recommended is Gas Tungsten Arc Welding (GTAW, also known as Tungsten Inert Gas or TIG). This is preferrable to other welding processes, such as Gas Metal Arc Welding (GMAW) or Shielded Metal Arc Welding (SMAW), for the best results.