Monel K500
Monel K500 is an age-hardenable nickel-copper alloy. It has the same corrosion resistance as Monel 400 but with much higher strength. The added strength comes from precipitation of Ni3 (Al, Ti) intermetallic particles during ageing. Yield strength can reach 790 MPa in the age-hardened condition, making K500 well-suited for high-load structural parts in marine environments.
1. Chemical Composition
The table below lists the elemental ranges for Monel K500. The aluminium and titanium additions enable precipitation hardening, which is what separates K500 compositionally from Monel 400.
| GRADE | UNS Designation |
Standard (Pipe) |
Chemical Requirement (Max) | |||||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Fe | Ti | Al | Co | ||||
| Monel K-500 | N05500 | 0.20 | 1.50 | 0.015 | 0.50 | min 63.0 | 27.0-34.0 | 0.5-2.0 | 0.3-1.0 | 2.2-3.5 | ||||||
2. Equivalent Grade
The table below cross-references Monel K500 with international grade designations. This alloy has limited direct equivalents because of its proprietary age-hardening chemistry.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Monel K-500 | N05500 | 2.4375 | NICu30Al | NICu30Al | NW 5500 | NA 18 | НМЖМц28-2.5-1.5 |
3. Key Technical Advantages
- Precipitation Hardening Without Sacrificing Corrosion Resistance: The Al and Ti additions (2.3–3.15% Al, 0.35–0.85% Ti) precipitate Ni3(Al, Ti) during controlled ageing at 580–620°C. This raises the yield strength to ≥690 MPa while keeping corrosion resistance identical to Monel 400 in marine and reducing acid environments.
- Non-Magnetic at Service Conditions: K500 is effectively non-magnetic in its annealed state. This property is used in applications that need non-magnetic structural components near sensitive instruments, such as downhole measurement-while-drilling (MWD) tools.
- Wear and Galling Resistance: The hardened microstructure greatly improves resistance to metal-to-metal wear and galling compared to Monel 400. This allows K500 to be used as shaft and bearing material in pump assemblies operating in abrasive seawater or produced fluid streams.
- Technical Note: Monel K500 is susceptible to hydrogen embrittlement when cathodically protected in seawater. When designing fasteners and shafts for offshore structures that use cathodic protection in seawater, engineers must consider the risk of hydrogen embrittlement and set suitable hardness limits (usually 35 HRC or lower) in line with NACE MR0175 or ISO 15156.
4. Common Manufacturing Standards
- ASTM B865: Standard specification for nickel-copper-aluminium alloy (UNS N05500) rod, bar, wire, and forging stock. This is the primary product standard for Monel K500 in bar/rod form, used to produce shafts, fasteners, and machined components.
- ASTM B163: Applicable to Monel K500 in seamless heat exchanger tube form where both high strength and corrosion resistance are needed.
- DIN 17752 / EN 10095: European standards for nickel alloy bars and tubes; K500 is designated 2.4375 under EN material numbering.
- JIS H4552: Japanese Industrial Standard for nickel and nickel alloy tubes; NW5500 designation applies to K500 tubular products.
- NACE MR0175 / ISO 15156: K500 fasteners and components for sour service are governed by hardness and heat treatment requirements in this standard, with maximum hardness limits to prevent hydrogen embrittlement.
Manufacturing Standards Comparison Table:
| tandard | GB | EN/DIN | JIS | GOST |
| ASTM B865 (Bar/Rod) | - | DIN 2.4375 | JIS H4552 (NW5500) | ГОСТ / МНА 27-2.5 |
| ASTM B163 (Tube) | - | EN 10216-5 (2.4375) | JIS H4552 | - |
5. Primary Applications
- Offshore Pump Shafts and Impellers: Seawater lift pump shafts, wear rings, and impeller hubs where high yield strength, non-magnetic behaviour, and seawater corrosion resistance must all be present in one material.
- Downhole Drilling Equipment: Non-magnetic drill collars, stabilisers, and MWD/LWD tool housings in directional drilling assemblies. The non-magnetic property prevents interference with survey instruments.
- Marine Fasteners: Propeller shaft nuts, keel bolts, and through-hull fasteners in naval and commercial vessels where both tensile load capacity and seawater corrosion resistance drive fastener material selection.
- Oil and Gas Production: Valve stems, mandrels, and completion equipment components in production wells handling chloride-rich produced fluids and H2S, subject to NACE MR0175 hardness controls.
- Chemical Process Machinery: Agitator shafts, pump casings, and rotating equipment components in HF, HCl, and brine processing environments use K500 for corrosion resistance and high-pressure stability.