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Everything You Need to Know About Monel

Everything you need to know about monel

When you’re deciding which metal to use for precision parts, the options can easily seem overwhelming. Each type of metal varies in cost, machinability, durability, weight, and more.

Since the majority of metals used in machining are alloys, they each contain different elements and compositions. You’ve probably heard about different grades of metals, such as 316 and 304 stainless steel, or 360 vs 353 brass.

In this article, we’ll give you an overview of Monel, a nickel alloy that Spex commonly uses to machine precision parts.

Monel is a nickel-copper alloy that’s well-known for its excellent corrosion resistance. This type of metal is resistant to corrosion from saltwater or seawater which makes it a good choice for parts in marine applications.


If you’re researching and comparing metals for precision machined parts, stainless steel was likely the first option you came across. Stainless steel is one of the most popular materials used, but it’s not perfect for every type of project. There are many other metals and alloys that you may be unfamiliar with. One of these lesser-known alloys is Monel.

You won’t find Monel parts or other superalloys on the shelves at Home Depot.

Monel is a nickel-based alloy, which is a more exotic and expensive material of construction than steel alloys—which is mostly iron. To give a comparison, nickel prices are around $8-9 per pound, while iron ore costs $0.08 per pound.

Monel is a trademarked name that refers to a group of copper-nickel alloys. This alloy is much stronger than nickel alone, highly resistant to corrosion, and highly weldable.

Spex uses Monel to machine custom fittings, adapters, manifolds, precision screws, pins, and nuts.

Read on to learn more about Monel and its applications in the world today.

Strength and durability

Superalloys like Monel are commonly used in the oil and gas industry, chemical and petrochemical processing, power plants, and other harsh environment applications. Metals and metal alloys are tested in a few different ways to determine their strength and durability. This includes testing the yield strength, tensile strength, and corrosion resistance.

Yield Strength of a material is calculated as the stress the metal, or in this case, alloys can withstand without permanent deformation.

The tensile strength of a material is the maximum stress which the alloy can endure while it is being stretched or pulled prior to either failure or break.

Corrosion resistance is how well the metal will hold up in a corrosive environment where acid, saltwater, or gas and oil are present.

Monel is a nickel-based alloy that has excellent corrosion resistance. Specifically, Monel alloy 400 is notable for its toughness, which is sustained across a wide range of high and low temperatures.

We call Monel a superalloy because it can maintain its strength in harsh environments with high temperatures, high stresses, and highly oxidizing atmospheres. Monel has yield strengths up to 350MPa, and tensile strength around 550MPa.

Monel alloys

Monel refers to a group of alloys which all contain about 63% Nickel and 30-35% Copper. The other 2-5% is a combination of Iron, Manganese, Silicon, Aluminum, and Titanium. Just like stainless steel has different alloys (316, 404, 304, etc.) Monel has 5 common alloys.

Monel 400: This alloy has good ductility and thermal conductivity. Monel 400 typically finds application in marine engineering, chemical and hydrocarbon processing, heat exchangers, valves, and pumps.

Monel 401: This alloy is designed for use in specialized electronic applications. Monel 401 is readily autogenously welded by the gas-tungsten-arc process.

Monel 404: The composition of Monel 404 is carefully adjusted to provide a very low Curie temperature, low permeability, and good brazing characteristics. This alloy can be welded using common welding techniques and forged but cannot be hot worked

Monel 405: Monel 405 is the free-machining grade of alloy 400. The nickel, carbon, manganese, iron, silicon, & copper percentages are the same as 400, but the sulfur is increased from a 0.024% max to 0.025-0.060%. Alloy 405 is used for automatic screw machine stock and is not usually recommended for other applications.

Monel K-500: Monel K-500 combines the excellent corrosion resistance characteristic of Monel alloy 400 with the added advantages of greater strength and hardness. The increased properties are obtained by adding aluminum and titanium to the nickel-copper base, and by heating under controlled conditions

Industries and applications

Since Monel is significantly more expensive compared to other options, it’s limited to uses where a cheaper alternative can’t be used. Monel is used in the aerospace industry, oil production and refining, marine equipment, and in some instruments.

Monel is perhaps the most resistant of all commonly used engineering alloys. The alloy is also resistant to many forms of sulfuric and hydrochloric acids under reducing conditions. This makes Monel parts useful in the oil and gas industry where harsh chemicals are used for long periods of time.

In the aerospace industry, Monel parts have been used in planes since the 1960s. Monel maintains its strength at very high temperatures, allowing it to maintain shape at high-speed flights. The higher strength equals out against the increased weight of the parts due to Monel’s higher density.

Monel is also used in marine applications such as piping systems, pump shafts, seawater valves, trolling wire, and housings for measurement equipment. In recreational boating, Monel is used for wire to seize shackles for anchor ropes, for water and fuel tanks, and in underwater applications.

Machining capabilities

Monel alloys require more work to machine compared to iron-based parts due to its higher strength. Machining precision Monel parts requires heavy-duty machines and tooling. Monel can be used to machine the same types of parts as stainless steel. Because of the increased hardness, there are additional costs when machining Monel parts.

As we mentioned, Monel 405 has a higher percentage of sulfur which makes it easier to machine. Monel K-500 is the most difficult to machine because it’s the hardest.

The tools we use to machine Monel spin faster and need to be changed more frequently to maintain tight tolerances. Spex uses the latest CNC machining processes to manufacture custom Monel parts, including fasteners, pins, fittings, adapters, connectors, housings, and more. 

We will work with your team to decide if Monel is the best choice for your project. We will also decide on the best machining process based on the part design and quantity of parts you need.

Contact us

Talk with one of our team members if you have any questions about ordering precision metal parts.

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