Monel 400 vs Inconel 625 – What’s the Difference

Monel 400 vs Inconel 625

Monel 400 and Inconel 625 have been used for various applications in different industries as two of the most popular nickel-based alloys. Despite having some similarities, Monel 400 and Inconel 625 differ mainly in their composition and properties. This blog post will delve into the details and compare Monel 400 and Inconel 625 regarding their chemical composition, physical properties, corrosion resistance, and applications.

Difference Between Monel 400 and Inconel 625

Chemical Composition

Monel 400 is a nickel-copper alloy composed of approximately 67% nickel, 23% copper, and small amounts of iron, manganese, carbon, and silicon. On the other hand, Inconel 625 is a nickel-based superalloy with a composition of approximately 61% nickel, 21% chromium, 9% molybdenum, and small amounts of niobium, iron, and titanium. The chemical composition of Inconel 625 gives it a higher strength than Monel 400.

Physical Properties

Monel 400 has a density of 8.83 grams per cubic centimeter (g/cm³), a melting point of 1300-1390°C, and a maximum operating temperature of 550°C. Inconel 625 has a density of 8.44 g/cm³, a melting point of 1290-1350°C, and a maximum operating temperature of 980°C. Therefore, Inconel 625 is more suitable for high-temperature applications, while Monel 400 is more suitable for low-temperature applications.

Corrosion Resistance

Monel 400 has excellent corrosion resistance in various environments, including seawater, hydrofluoric acid, sulfuric acid, and alkalies. In comparison, Inconel 625 has even better corrosion resistance in harsh environments with high temperatures and pressures, such as oil and gas, chemical processing, and nuclear power plants. Inconel 625 also has resistance to pitting, crevice, and intergranular corrosion.

Applications

Monel 400 is commonly used in marine, aerospace, chemical, and petrochemical industries for pumps, valves, heat exchangers, fasteners, and seawater-resistant equipment. In comparison, Inconel 625 is commonly used in extreme conditions, such as high-temperature and high-pressure applications, aerospace, chemical processing, and nuclear power generation. Inconel 625 is also used for welding and cladding applications.

Cost

Lastly, Monel 400 is generally less expensive than Inconel 625 due to its lower nickel content and simpler composition. However, the cost may vary depending on the availability, demand, and production process.

Conclusion:

In conclusion, Monel 400 and Inconel 625 have different compositions, properties, and applications. Monel 400 is more suitable for low-temperature applications and has excellent corrosion resistance in seawater and alkalies. In contrast, Inconel 625 is more suitable for high-temperature and high-pressure applications and has better corrosion resistance in harsh environments with chemicals and acids. The choice between Monel 400 and Inconel 625 should depend on the specific requirements and conditions of the application, including temperature, pressure, operating environment, and budget.

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