Material Family

Nickel-Copper-Aluminum-Titanium Alloy (Precipitation-Hardenable)

A high-strength version of the Monel family, gaining properties via heat treatment.

Common Designations

UNS N05500, Monel K-500, W.Nr. 2.4375

The high-strength, corrosion-resistant nickel-copper alloy. "Monel" is a trademark of Special Metals Corporation.

Distinguishing Feature

High Strength & Hardness combined with excellent corrosion resistance. Can be heat treated to achieve properties similar to quenched-and-tempered alloy steels.

This is the primary reason to choose K-500 over Monel 400 or R-405.

Chemical Composition (Typical wt.%)

Ni: ≥ 63.0 (Balance)
Cu: 27.0 - 33.0
Al: 2.30 - 3.15
Ti: 0.35 - 0.85
Fe: 2.0 max
Mn: 1.5 max
C: ≤ 0.25
Si: ≤ 0.50

The additions of Aluminum (Al) and Titanium (Ti) enable age-hardening by forming the γ' (Ni₃(Al,Ti)) strengthening precipitates.

Mechanical Properties (Aged Condition - Typical)

Tensile Strength (Rm): 965 - 1200 MPa
Yield Strength (Rp0.2): 690 - 965 MPa
Elongation (A): 20 - 30%
Hardness: 25 - 35 HRC

Strength is approximately double that of annealed Monel 400, with good retained ductility.

Physical Properties

Density: 8.44 g/cm³
Melting Range: 1315 - 1350 °C
Useful Service Range: Cryogenic to about 480°C (900°F), beyond which overaging occurs.

Maintains its enhanced strength in typical service environments.

Key Performance Attributes

• Excellent resistance to seawater and marine atmospheres (similar to Monel 400). Resists chloride stress corrosion cracking.
• High strength-to-weight ratio, excellent fatigue strength, and low magnetic permeability.

• Good resistance to hydrofluoric acid, alkalis, and many organic acids.

• Poor resistance to oxidizing acids (e.g., nitric acid).

Combines marine-grade corrosion resistance with the strength of steel.

Heat Treatment Condition

Supplied in solution annealed or hot worked condition for fabrication. Final high strength is achieved by a two-step aging treatment (e.g., 595°C/16hrs, air cool).

Critical: Like other PH alloys, final aging is typically done post-fabrication/machining to develop full properties.

Key Standards (Plate)

ASTM B865 (Standard Specification for Precipitation Hardening Nickel-Copper-Aluminum Alloy Plate, Sheet, and Strip), AMS 4676 (Aerospace)

ASTM B865 is the primary material specification for plate and sheet forms.

Typical Applications

• Marine Engineering: High-strength propeller shafts, pump rods, fasteners, mooring cables, seawater valve stems.
• Oil & Gas: Drill collars, non-magnetic logging tools, wellhead components, springs in sour service.
• Aerospace: Turbocharger seals, fuel pump parts.
• Chemical Processing: High-strength shafts and impellers for corrosive services.

The go-to material for critical, high-strength rotating components and fasteners in seawater and sour service environments.