What are nickel based alloys used for?
Copper nickel alloys have an excellent resistance to corrosion.......
And thus these materials are used extensively in saltwater environments.
These alloys are also used for currency, for which corrosion resistance and inherent hardness makes this alloy particularly suited.
Alnico alloys (alloys of nickel, cobalt, and nickel) are used for permanent magnets.
This list is not exhaustive.