Monel K-500

Monel® K500 (also known as Super Alloy Nickelvac K-500) is a precipitation-hardenable nickel-copper alloy that combines the excellent corrosion resistance characteristic of Monel® 400 with the added advantage of greater strength and hardness. These amplified properties, strength, and hardness, are obtained by adding aluminum and titanium to the nickel-copper base and by a thermal processing used to effect precipitation, typically called age hardening or aging. When in the age-hardened condition, Monel® K-500 has a greater tendency toward stress-corrosion cracking in some environments than Monel® 400. Alloy K-500 has approximately three times the yield strength and double the tensile strength when compared with alloy 400. Additionally, it can be further strengthened by cold working prior to precipitation hardening. The strength of Monel® K500 is maintained to 1200° F but stays ductile and tough down to temperatures of 400° F. Its melting range is 2400-2460° F.

Monel® K-500 is spark resistant and non-magnetic to -200° F. However, it is possible to develop a magnetic layer on the surface of the material during processing. Aluminum and copper may be selectively oxidized during heating, leaving a magnetic nickel rich film on the outside. Pickling or bright dipping in acid can remove this magnetic film and restore the non-magnetic properties.

The corrosion resistance of alloy K-500 is substantially equivalent to that of Monel® 400 except that when in the age-hardened condition, nickel alloy K-500 has a greater tendency toward stress-corrosion cracking in some environments. Monel® K-500 has been found to be resistant to a sour-gas environment. The combination of very low corrosion rates in high-velocity sear water and high strength make Monel® K-500 particularly suitable for shafts of centrifugal pumps in marine service. In stagnant or slow-moving sea water, fouling may occur followed by pitting but this pitting slows down after a fairly rapid initial attack.