Monel K 500
Monel Nickel-Copper Alloy K-500 combines the superior corrosion resistance properties of Monel Alloy 400 with the added advantages of greater strength and hardness. The increased properties are obtained by adding aluminum and titanium to the nickel-copper base and heating under controlled conditions to precipitate submicro particles of Ni3(Ti, Al) throughout the matrix. Heat treatment that affects precipitation is commonly referred to as aging hardening or aging.
Type Analysis
Applications
Typical uses for alloy K-500 are pump shafts and impellers, doctor blades and scrapers, oil well drill collars and instruments, electronic components, springs and valve trims.
Corrosion Resistance
The corrosion resistance of Monel alloy K-500 is nearly identical to that of alloy 400, except that alloy K-500 is more prone to stress-corrosion cracking under hardened conditions under some circumstances.
Monel alloy K-500 has been found to be resistant to sour gas environments.
After continuous immersion for 6 days in saturated (3500 ppm) hydrogen sulfide solution at acidic and basic pH (ranging from 1.0 to 11.0), the U-bend sample of the aging-hardened sheet showed no cracks. There were black scales attached to something.
The hardness of the sample was 28-40 Rc.
The combination of very low corrosion rates and high strength in high-speed seawater makes Alloy K-500 particularly suitable for centrifugal pump shafts in marine service.
Stagnant or slow-moving seawater can cause fouling followed by pitting, but this pitting slows down after a fairly quick initial attack.
