Mechanical properties, ductility and resistance of MONEL nickelalloy
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MONEL nickelalloy is known for its toughness, hardness and resistance, making it a popular material in many industrial applications. MONEL series alloys have been in existence for more than 100 years. It was originally created in 1901 by Robert Crooks Stanley, who is sometimes considered the “grandfather of the nickel industry.” It was developed while he was working for INCO and was patented in 1906.
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This valuable steel grade is mainly composed of nickel and copper and is a good substitute for commercial pure nickel, providing similar corrosion resistance in a more economical way. The mixture of nickel and copper is mixed with carefully controlled amounts of other elements, including iron, manganese, silicon, carbon and sulfur, which together give the MONEL series of alloys unique properties.
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One of the advantages of this alloy over commercial pure nickel is that it is stronger and easy to manufacture for a variety of end uses. Taking into account that nickel and copper are mutually soluble in all proportions, it is a single-phase alloy that can be used in environments with high corrosion or extreme temperature ranges.
MONEL400 alloy
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MONEL400 alloy was created as a binary alloy with the same ratio of nickel and copper as the ratio naturally occurring in meteor nickel ore. This means that it is considered a “pure alloy”, or something found in its pure form in nature.
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MONEL400 alloy is the basis of the MONEL series of products, and professional versions have been created in the years since its establishment. For example, MONEL401 alloy is designed for electrical and electronic applications. MONEL404 alloy is commonly used for transistors and other such precision components, and benefits from a very carefully balanced and controlled version of this technology alloy. MONEL 405 alloy is a free processing grade of the original alloy, with only sulfur added to meet very special needs-usually automatic screw machine stock. MONEL450 alloy is especially suitable for seawater applications and brine pipelines. Each version of the original MONEL product has similar required mechanical and chemical properties. -
The excellent mechanical properties of MONEL400 alloy means that it is usually used at sub-zero temperatures, at which temperature its strength and hardness will increase, but its ductility is very small. Under these conditions, many other materials undergo a transition from toughness to brittleness at such low temperatures. In terms of shear strength, the previous U.S. Navy tear test lowered the material to a temperature of -320°F. The material maintained excellent ductility. As the temperature decreased, its maximum load increased significantly.
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This is also a material known for its excellent toughness and impact strength, which can be maintained in a wide temperature range. It can be used in high temperature applications up to 1,000°F under oxidizing conditions and even higher under reducing conditions.
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Therefore, it is not surprising that MONEL nickelalloy is used in the aerospace industry, where strength and resistance are the main factors in material selection. In the 1960s, it was widely used in aircraft manufacturing, including experimental projects such as the North American X-15. Today, it is still used in aerospace for critical wiring under high temperature conditions, although stainless steel wire is also used in other areas to save costs.
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In the past 100 years, it has been used in the oil and gas industry, mainly for oil tower internals, fasteners and accessories, and pumps. Another important use is to protect the splash zone and marine structures on the seabed. It has been found to provide good corrosion protection and resistance to physical damage.
MONEL K-500 alloy
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Although the mechanical properties of the MONEL400 alloy are impressive enough, one of the most commonly used versions of this grade is the precipitation-strengthened MONEL nickelalloy K-500. The significant difference is that the composition contains small, controlled amounts of titanium and aluminum. They are added to the basic MONEL400 alloy mixture during the melting process in order to make the material have higher strength and hardness without compromising its excellent corrosion resistance.
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As the MONEL mixture is heated and other elements are added, submicroscopic particles of titanium and aluminum will precipitate out throughout the alloy matrix. This age hardening gives way to the MONEL nickelalloy, which is usually required for extra hardness of pump shafts, scrapers, oil well drill collars and electronic components.
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MONEL nickelalloy K-500 performs well in testing its mechanical properties. Its tensile strength and yield strength increase with the decrease of temperature, but have little effect on ductility or toughness. Even at low temperatures, it avoids the transition from ductility to brittleness. Extensive tests have also been conducted on its shear strength, impact strength and fatigue strength, and the results show that it can provide excellent overall strength. All results can be viewed in the material data sheet.
Comparison between MONEL materials
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Compared with MONEL400 alloy, MONEL nickelalloy K-500 has higher fatigue strength (230-290 MPa and 260-560 MPa), shear strength (370-490 MPa and 430-700 MPa) and tensile strength (final) UTS; 540-780 MPa and 310-880 MPa).
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However, the choice of material between MONEL400 alloy and MONEL nickelalloy K-500 depends largely on the final application. Although K-500 has higher mechanical toughness and hardness, it is more susceptible to stress corrosion cracking in certain environments.
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Although the Curie temperature of MONEL400 alloy is higher (40°C vs -67°C), the Curie temperature is higher and the material loses permanent magnetic properties. The thermal properties of the two are roughly similar. In terms of electrical characteristics, they are also almost the same.
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In many situations and applications, the combination of MONEL400 alloy and alloy K-500 can play their respective advantages in the right area of the project.
