How hard is Monel K500?
Description
Monel Nickel-Copper Alloy K-500 combines the excellent corrosion resistance characteristics of Monel Alloy 400 with increased strength and hardness. The higher properties are obtained by adding aluminum and titanium to the nickel-copper matrix and heating under controlled conditions to precipitate submicroscopic particles of Ni3 (Ti, Al) throughout the matrix. The heat treatment used to produce the precipitation is generally referred to as age hardening or aging.
Applications
Typical applications for K-500 alloy are pump shafts and impellers; scrapers and scrapers; oil well drill collars and instrumentation; electronic components; springs; and valve trim.
Corrosion Resistance
The corrosion resistance of Monel Alloy K-500 is roughly equivalent to that of Alloy 400, except that in the age-hardened condition, K-500 alloy is more susceptible to stress corrosion cracking in certain environments. Monel Alloy K-500 has been found to withstand sour gas environments. U-bend specimens of age-hardened plate showed no cracking after 6 days of continuous immersion in saturated (3500 ppm) hydrogen sulfide solutions at acidic and alkaline pH values (ranging from 1.0 to 11.0). There were some tightly adhered black scales. The hardness of the specimens ranged from 28 to 40 Rc.
The extremely low corrosion rate and high strength in high velocity seawater make K-500 alloy particularly suitable for shafts in marine centrifugal pumps. In stagnant or slowly moving seawater, fouling may occur, followed by pitting, but this pitting slows down after a fairly rapid initial attack.
