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 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.
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.