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Material Specification

Alloy K500

Alloy K500 Fasteners
Nickel-Copper Precipitation Hardened – Highest Strength Monel for Subsea & Pump Shafts

Monel Alloy K500 Fasteners

Buy Monel K500 (UNS N05500 / Werkstoff 2.4375 / ASTM B865 / AMS 4676) bolts, stud bolts, pump shaft bolting, and precision fasteners from Exotic Alloy. Monel K500 is the precipitation-hardened version of Monel 400, with 2.7–3.15% Al and 0.35–0.85% Ti additions that enable age-hardening to yield strengths of 585–690 MPa — approximately 3× the strength of annealed Monel 400 — while retaining outstanding corrosion resistance in seawater and reducing media.

Exotic Alloy manufactures Monel K500 fasteners per ASTM B865, AMS 4676, and NACE MR0175 / ISO 15156-3 for subsea offshore pump shafts, propeller shaft bolting, impeller stub shafts, marine deck hardware, downhole valve trim, and any application combining the corrosion resistance of Monel 400 with high mechanical strength.

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Product Range

Alloy K500 Fasteners Available

Alloy K500 Hex Bolts
Alloy K500
Hex Bolts
Alloy K500 Heavy Hex Bolts
Alloy K500
Heavy Hex Bolts
Alloy K500 Stud Bolts
Alloy K500
Stud Bolts
Alloy K500 Threaded Rods
Alloy K500
Threaded Rods
Alloy K500 Anchor Bolts
Alloy K500
Anchor Bolts
Alloy K500 Hex Nuts
Alloy K500
Hex Nuts
Alloy K500 Washers
Alloy K500
Washers
Alloy K500 Cotter Pins
Alloy K500
Cotter Pins
Alloy K500 Springs
Alloy K500
Springs
Alloy K500 Circlips
Alloy K500
Circlips
Alloy K500 Coated Fasteners
Alloy K500
Coated Fasteners
Alloy K500 Custom Spacers
Alloy K500
Custom Spacers
Technical Data

Alloy K500 Specifications

Chemical Composition — Monel Alloy K500 (wt. %)
ElementNiCuAlTiFeMnSiCS
Min %63.0027.002.300.35–––––
Max %Balance33.003.150.852.001.500.500.250.010
Mechanical Properties — Monel Alloy K500
ConditionUTS (MPa)YS 0.2% (MPa)Elongation (%)Hardness
Annealed (Solution Treated)690–760310–38025–35≤ 185 HB
Age-Hardened (Standard / AMS 4676)960–1030690–76018–25≤ 305 HB / ≤ 30 HRC
Cold-Worked + Aged (Max Strength)1100+850+12–18≤ 36 HRC
Physical Properties
Density8.44 g/cm³
Melting Range1315–1350°C (2399–2462°F)
Specific Heat Capacity419 J/kg·K at 20°C
Thermal Conductivity17.5 W/m·K at 100°C
Thermal Expansion13.7 µm/m·°C (20–100°C)
Electrical Resistivity0.615 µΩ·m
Equivalent Grades & Standards
UNSWerkstoff / DINEN / BSAFNOR
N05500 2.4375 NiCu30Al NU30AT

Key Specifications: ASTM B865 (Bar/Rod) / AMS 4676 (Bar) / AMS 7233 (Forgings) / NACE MR0175

Machinability: Monel K500 is best machined in the annealed condition prior to aging. In the aged condition it is significantly harder and work-hardens rapidly — use carbide tooling, low speeds (40–70 SFM), heavy feeds, and high-pressure flood cooling. All precision threads should be cut before the final aging heat treatment. Grinding after aging is the preferred method for finish-dimension control.

Welding: Weld with GTAW using ERNiCu-7 filler wire (Monel 60) in the annealed condition only. Welding aged K500 is not recommended due to strain-age cracking risk. Post-weld solution anneal at 980°C for 1 hour followed by the standard aging treatment (595°C / 16h) restores full mechanical strength. Keep inter-pass temperature below 100°C.

Forging: Hot forge between 955–1175°C (1750–2150°F). Alloy K500 has good hot workability in this range. After forging, solution anneal at 980°C (1800°F) / 1 hour, water quench. Then age harden at 595°C (1100°F) / 16 hours, air cool for standard properties (AMS 4676).

Heat Treatment: Solution anneal at 980°C (1800°F) / 1 hour minimum, water quench. Age harden at 595°C (1100°F) / 16 hours, air cool. This treatment produces the standard AMS 4676 / ASTM B865 aged properties. For maximum strength, cold work 15–20% between the anneal and age steps. Hardness after aging shall not exceed 35 HRC for NACE MR0175 compliance.

Monel K500 maintains the same corrosion resistance characteristics as Monel 400 across all environments — seawater, HF acid, alkalis, and reducing media — while providing approximately 3× the yield strength. Per NACE MR0175 / ISO 15156-3, K500 in the age-hardened condition with hardness ≤ 35 HRC is qualified for sour (H₂S) service. Superior resistance to seawater biofouling, erosion-corrosion, and stress corrosion cracking versus higher-strength steels.

Key Characteristics

  • Outstanding resistance to seawater, brine, and hydrofluoric acid corrosion.
  • High nickel base provides immunity to chloride stress-corrosion cracking.
  • Good mechanical strength retainable from cryogenic temperatures to ~480°C.
  • Excellent resistance to alkalis, caustic soda, and reducing acids.
  • Superior biofouling resistance and marine corrosion resistance.

Typical Applications

  • Marine engineering: propeller shafts, pump shafts, and ship hardware.
  • Desalination plants: brine heater bolting and flash chamber hardware.
  • Offshore oil & gas: subsea Christmas tree fasteners and wellhead hardware.
  • Chemical processing: hydrofluoric acid plant bolting and valve components.
  • Naval engineering: submarine hull fittings and seawater system hardware.