Overview
Monel is a corrosion resistant nickel alloy. It is often used in marine and electronic components. Monel is often more than ten times more expensive than stainless steel. You may be wondering:
Why should I use the more expensive Monel alloy instead of stainless steel when it is also a corrosion resistant metal?
What is the role of the chemical composition of Monel alloys?
In this article, we will look at three aspects of Monel alloys in detail.
What is Monel?
Monel is a general term for a range of nickel-copper alloys. As such, it can be said that Monel is primarily composed of the elements nickel and copper. Of course, there are some differences in the composition of different Monel alloys, and these differences form different grades. Below are the common Monel grades:
These different grades have different performance characteristics. Therefore, they are suitable for different applications. Below, we understand the differences between the different grades from three aspects: chemical composition, mechanical properties and physical properties.
Chemical Composition of Monel
Nickel
Nickel is the main element of Monel alloys. As a matrix, the most important role of nickel in Monel alloys is to stabilize the austenitic structure. This structure gives the alloy excellent plasticity and strength, and it gives the alloy the most balanced properties.
In addition, nickel has excellent corrosion resistance. This is part of the source of the corrosion resistance of Monel alloys.
Compared to stainless steel, Monel alloys have a much higher nickel content. As a result, Monel alloys have better structural stability and base corrosion resistance than stainless steel.
Copper
Copper is the most characteristic element in Monel alloys. It also plays two important roles in Monel alloys:
First, copper has excellent oxidation resistance at room temperature. This also applies to Monel alloys containing copper. The oxidation resistance that copper brings to Monel alloys is extremely effective in flowing seawater. Therefore, Monel alloys are most widely used in marine applications.
In addition, copper is a very good conductor. This property makes it an excellent component for electronic components. Within Monel, there are two typical grades for electronic components: Monel 401 and Monel 404, which have a higher copper content than other Monel alloys.
In contrast to Monel alloys, the oxidation resistance of stainless steels is mainly due to chromium. As a result, Monel alloys have different application areas than stainless steel. In general, however, the corrosion resistance of Monel is better than that of stainless steel.
Aluminum and Titanium
Aluminum and titanium in Monel alloys mainly play the role of precipitation strengthening. These two elements increase the strength of the alloy considerably.
In stainless steel, aluminum, niobium and tantalum play this role.
Mechanical Properties of Monel
Depending on the type of strengthening, Monel alloys can be divided into two broad categories: solid solution strengthened alloys and precipitation strengthened alloys. There are two ways to distinguish between these two categories of alloys:
Monel alloys can be distinguished from the categories by their naming. Alloys whose names begin with 4 are solid solution strengthened alloys. For example, Monel 400, Monel R-405. Alloys beginning with 5 are precipitation strengthened alloys. For example: Monel 502, Monel K-500.
Monel alloys can also be categorized by their chemical composition. As mentioned above, aluminum and titanium are important precipitation strengthening elements in Monel alloys. Therefore, alloys containing aluminum and titanium are precipitation strengthened alloys. The opposite is solid solution strengthened alloys.
Among Monel alloys, solid solution strengthened alloys have better plasticity and precipitation strengthened alloys have higher strength. As a result, the former are mainly used for housings or pipes in various marine applications and for various wires in electronic components, while the latter are mainly used for components that need to withstand pressure, such as fasteners in marine applications.
The following table compares the mechanical properties of Monel alloys:
| Alloy | Category | Tensile Strength | Yield Strength | Elongation |
|---|---|---|---|---|
| MPa | MPa | % | ||
| Monel 400 | Solid Solution Strengthened Alloy | 480 | 170 | 35 |
| Monel 401 | Solid Solution Strengthened Alloy | 441 | 134 | 51 |
| Monel R-405 | Solid Solution Strengthened Alloy | 480 | 170 | 35 |
| Monel K-500 | Precipitation Strengthened Alloy | 1000 | 760 | 35 |
| Monel 502 | Precipitation Strengthened Alloy | 1158 | 1034 | 15 |
Physical Properties of Monel
In Monel alloys, the two most important physical properties are density and Curie temperature.
Density determines the weight of the alloy. In Monel alloys, both copper and nickel have higher densities. Therefore, solid solution strengthened alloys have higher density. Whereas precipitation strengthened alloys contain low density metals aluminum and titanium. This makes them even less dense.
You can use the following tools to quickly calculate the weight of different Monel alloys:
Curie temperature determines the magnetic properties of the alloy. Since Monel alloys are used at room temperature, alloys with a Curie temperature below room temperature are non-magnetic, e.g. Monel 401 / 404. Their non-magnetism is necessary for their use as electronic components. Monel 400, on the other hand, has a higher Curie temperature than room temperature and its magnetic properties make it more suitable for marine applications.
FAQ
Is Monel a superalloy?
By definition, superalloy is an alloy that is used at high temperatures. Since copper loses its oxidation resistance at high temperatures, Monel is not suitable for long-term use at high temperatures. Therefore, Monel alloys are nickel alloys, but not superalloys.
What is the difference between Monel and copper-nickel alloys?
Monel is a nickel-copper alloy. Compared to copper-nickel alloys, Monel alloys contain more nickel than copper. Therefore, Monel is a nickel alloy. While copper-nickel alloy has more copper than nickel content. It is a type of copper alloy.
What product forms are Monel alloy available in?
Monel alloys are available in most common product forms. For example: seamless pipe & tube, round bar & rod, sheet & plate, strip & wire.
You can also refer to our website for a more detailed listing of Monel products:
Monel Nickel Alloy -- Grades & Products
Further Reading
Conclusion
Monel is a corrosion-resistant nickel-copper alloy used primarily in marine and electronic applications. Its corrosion resistance is superior to that of stainless steel. It is also much more expensive than stainless steel. However, it is irreplaceable. In practical applications, different grades of Monel alloys should be selected according to different strengths of use and magnetic properties.
We produce high performance Monel alloys. Please do not hesitate to contact us if you have any requirements.
