NiCu Alloys - Aircraft Carrier

Nickel-Copper Alloys

Nickel Copper alloys are an important sub-group of Nickel alloys that are frequently used throughout several industries. NiCu alloys can be used in different environments, such as those that contain reducing acids, alkalies, and seawater among others.  The most well known of this alloy group, N04400 or Alloy 400, is considered to be one of, if not the first nickel-base corrosion resistant alloy.

Alloy 400 (Monel)

Alloy 400 is a high strength corrosion resistant material that maintains relatively the same ratio of Ni to Cu as is found in the naturally occurring ore. Like other nickel alloys, it is a solid solution austenitic system that work hardens fast and cannot be hardened by heat treatment. It is used currently in different industries including, aerospace, oil field and marine and chemical engineering applications. Alloy 400 can be found in valves, pumps for mixing equipment, springs, fresh water tanks, processing tanks, heat exchangers and even electrical components. There are not many other alloys that can handle hydrofluoric acid as well Alloy 400 does. It is used in HF alkylation towers in chemical processing plants. The resistance to salts, specifically fluoride salts, make this alloy desirable in some nuclear applications where refining of uranium is required. The low Fe content allows this alloy to be used in food processing, where Fe contamination is a concern. This alloy also has a curie temperature range (70-120°F) that can cause issues if there is a strong non-magnetic requirement. This alloy is available in almost every product form including bar, sheet/plate, pipe/tube and fasteners, fittings and flanges. It is typically supplied in the annealed or stress relieved form. This is a very versatile alloy but two other alloys resulted from the attempt to improve this system.

Alloy 405 (Monel)

Alloy 405 (N04405) is a variant of Alloy 400 that has increased sulfur content to improve machinability. This alloy maintains the strength and corrosion resistance of traditional Alloy 400. This is considered a free machining grade. The added sulfur causes the material to develop sulfides that act as chip breakers, because of this the surface finish suffers.

Alloy K500 (Monel)

Alloy K500 is considered the high strength NiCu alloy. It was found that by the addition of aluminum and titanium to the core alloy it caused a hardening effect during subsequent heat treatments. This was unique for nickel alloys since most nickel alloys with a few exceptions are hardening only through introducing cold work. This alloy is very non-magnetic and some specifications require it maintain a less than 1.01 magnetic permeability. It also has the excellent corrosion resistance of Alloy 400 but with improved strength and hardness, this alloy can be used in other applications where Alloy 400 is limited. K500 can be found in many marine applications such as chains, cables, and fasteners to name a few. In chemical processing, many pump and valve internals are made from this alloy. This alloy can be supplied in the annealed, annealed and aged or direct aged conditions.



Mechanical Properties

mechanical properties

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A Century of Monel Metal, 1906-2006, by Lewis e. Shoemaker & Gaylord d. Smith, Huntington Alloys/Special Metals Corporation Huntington WV

History of Monel Alloy K500, by E.L. Hibner and Dr. T.F.Lemke,2011

Special Metals Company Alloy 400, R405 and K500 data sheets.