US Navy uses many metallic materials such as carbon steel, stainless steels, nickel alloys, copper
alloys, titanium & aluminum alloys in their ships. Some of the major concerns are pitting/crevice
corrosion, stress corrosion cracking, hydrogen embrittlement, ability to weld repair small worn and
corroded areas, prevention of galvanic corrosion and reliable usage of high strength fasteners. Even
though several stainless steels and nickel-based alloys have shown promise and are used in marine
environments, under very severe crevice corrosion conditions, most of these have suffered from
localized crevice attack, including high alloys like alloy 625 and alloy C-276. Fasteners of alloy K-500
have failed due to stress corrosion cracking. Alloy 718 fasteners suffer from localized attack. The
search for alloys that are essentially immune to crevice corrosion attack in marine environments and
provide reliable high strength fasteners for replacing K-500 fasteners , led the US Navy to consider Ni-
Cr-Mo alloys with the highest combination of chromium and molybdenum in a nickel matrix.