Monel K500
Monel K500 (UNS N05500) is a precipitation-hardenable nickel-copper alloy (65–70% Ni, 27–33% Cu, 2.3–3.15% Al, 0.35–0.85% Ti) that combines the exceptional seawater and salt atmosphere corrosion resistance of the Monel 400 family with significant strength from age hardening. In the aged condition, Monel K500 achieves tensile strengths of 140,000–160,000 psi — approximately twice the strength of annealed Monel 400 — while retaining full resistance to seawater corrosion, cavitation erosion, and stress corrosion cracking in most marine environments.
Monel K500 is unique among high-strength alloys in being essentially non-magnetic below −50°F, making it valuable for applications where magnetic interference must be avoided. QQ-N-286 governs procurement for marine and defense applications; AMS 4676 covers aerospace applications. Both specifications cover bar, rod, and wire forms, which are the primary product forms for machined aerospace and naval components.
Product Forms & Size Range of Monel K500
Monel K500 bar and rod per QQ-N-286 / AMS 4676 is available in round bar from 0.250″ to 10.000″ in the age-hardened condition. Used for precision machined shafts, fasteners, pump components, and valve stems in marine and aerospace systems. Hot-finished bar is available for forging stock in larger cross-sections.
HEAT TREATMENT OF MONEL K500
Monel K500 is annealed at 1800°F (982°C) for one hour per inch of thickness, water quenched, and then age-hardened (precipitation hardened) at 1100°F (593°C) for 16 hours, furnace cooled to 900°F at 15–25°F/hour, then air cooled. This aging cycle precipitates Ni₃(Al,Ti) particles that dramatically increase strength while preserving the Ni-Cu matrix's corrosion resistance. For maximum strength, a double-age cycle may be used. Cold working before aging further increases the age-hardened strength.
APPLICATIONS OF MONEL K500
Monel K500 is used for marine propeller shafts and pump shafts in seawater service, impellers and wear rings in seawater pumps, fasteners for deep-sea oil and gas equipment, naval sonar transducer housings where non-magnetic property is required, aircraft fuel system components in marine environments, valve stems for shipboard saltwater systems, and offshore oil platform components requiring the combination of high strength and outstanding seawater corrosion resistance.
Monel 400
Annealed Ni-Cu alloy — lower strength than K500 but the broadest corrosion resistance in the Monel family, used for sheet and plate applications.
Inconel 718
Precipitation-hardenable Ni-Cr-Mo alloy achieving 180–200 ksi — used where higher strength than Monel K500 is required alongside good corrosion resistance.
Certified Material for Critical Service
Monel K500 is supplied to QQ-N-286 (federal specification — marine/defense applications) and AMS 4676 (aerospace applications). Mill certifications document full chemistry including aluminum and titanium content, age-hardening treatment records, and mechanical properties (minimum yield 110 ksi, minimum tensile 140 ksi in aged condition). NACE MR0175 compliance is available for oil and gas sour service applications.