Monel® was created in 1905 by Robert Crooks Stanley, who was then employed by the International Nickel Company (Inco). Monel® alloy 400 is a binary alloy of the same ratio of nickel to copper as occurs naturally in the meteoritic nickel ore from the Sudbury (Ontario) mines and is therefore considered a puritanical alloy. Monel® was named for the company's president, Ambrose Monell, and patented in 1906. One L was omitted because family names were not allowed as trademarks at that time. The trademark was registered in May 1921, and the name is now a trademark of Special Metals Corporation.
Monel® is a group of alloys of nickel (from 52 to 67%) and copper, with small amounts of iron, manganese, carbon and silicon. Monel® is not a copper-nickel alloy because it contains less than 60% copper.
Stronger than pure nickel, Monel® alloys are resistant to corrosion by many aggressive substances, including fast-flowing seawater. They can be easily fabricated by hot and cold working, machining and welding.
Types of Monel® alloys
There are several commercial types of Monel® such as Alloy 400, Alloy R-405, Alloy K-500. Standard product shapes are round, hexagonal, flat, forging, pipe, tube, plate, sheet, strip and wire.
Monel® 400
Monel® nickel-copper alloy 400 (UNS N04400/W.No. 2.4360 and 2.4361) is a solid-solution alloy that can only be hardened by cold forming. It has high strength and toughness over a wide temperature range and excellent resistance to many corrosive environments.
Alloy 400 is used in many fields, especially marine and chemical processing. Typical applications include valves and pumps; pump and propeller shafts; marine fasteners and fasteners; electrical and electronic components; springs; chemical processing equipment gasoline and fresh water tanks; process vessels and piping; boiler feedwater heaters and other heat exchangers; and venting devices.
| Property | Value (Metric) | Value (Imperial) |
| Density | 8.80*103 kg/m3 | 549 lb/ft3 |
| Modulus of Elasticity | 179 GPa | 26,000 ksi |
| Thermal Expansion (20°C) | 13.9*10-6° C-1 | 7.7*10-6 in/(in*°F) |
| Specific Heat Capacity | 427 J/(kg*K) | 0.102 BTU/(lb*°F) |
| Thermal Conductivity | 21.8 W/(m*K) | 151 BTU*in/(hr*ft2*°F) |
| Electric Resistivity | 54.7*10-8 Ohm*m | 54.7*10-6 Ohm*cm |
| Tensile Strength (Annealed) | 550 MPa | 79,800 psi |
| Yield Strength (Annealed) | 240 MPa | 34,800 psi |
| Elongation | 48% | 48% |
| Liquid temperature | 1,350° C | 2,460° F |
| Solidus Temperature | 1,300° C | 2,370° F |
Monel® R405
Monel® nickel-copper alloy R405 (UNS N04405) is the free-machining grade of alloy 400. Its higher sulfur content increases machinability. It has essentially the same corrosion resistance and physical properties as alloy 400, but a slightly different set of mechanical properties. Alloy R405 is primarily used for automatic screw machine stock and is generally not recommended for other applications.
Monel® K500
Monel® alloy K500 (UNS N05500/W.No. 2.4375) is a nickel-copper alloy that combines the excellent corrosion resistance of Monel® alloy 400 with the added benefits of greater strength and hardness. The improved properties are obtained by adding aluminum and titanium to the nickel-copper base and by heating under controlled conditions so that submicroscopic particles of Ni3 (Ti, Al) precipitate throughout the matrix. The thermal process used to achieve precipitation is commonly referred to as aging or aging.
Typical applications for Monel® alloy K500 products are chains and cables, fasteners and springs for marine; pump and valve parts for chemical processing; doctor blades and scrapers for pulp processing in paper production; drill columns and drill collars and instruments, pump passes and impellers, non-magnetic housings, safety elevators and valves for oil and gas extraction; and and gas production; and sensors and other electronic components.