Ferralium 255 and Alloy 625: Alloys Engineered for Extreme Environments
In industries where equipment faces aggressive corrosion, high temperatures, and mechanical stress, selecting the right material is crucial. Ferralium 255 and Alloy 625 are two high-performance alloys that excel in such demanding conditions. Stocked by Langley Alloys, these materials are designed to withstand the harshest environments, ensuring longevity and reliability in critical applications.
Understanding PREN: A Measure of Corrosion Resistance
The Pitting Resistance Equivalent Number (PREN) is a formula used to assess the resistance of stainless steels and nickel alloys to pitting and crevice corrosion. It considers the concentrations of chromium (Cr), molybdenum (Mo), and nitrogen (N) in the alloy. While PREN provides a comparative measure, it’s important to note that it doesn’t account for all factors influencing corrosion resistance, such as the presence of copper or the specific environmental conditions.
Ferralium 255: With a PREN of approximately 40, this super duplex stainless steel offers excellent resistance to pitting and crevice corrosion, particularly in chloride-rich environments.
Alloy 625: Exhibiting a PREN around 45, this nickel-based superalloy provides superior corrosion resistance, especially in reducing environments and those containing sulphur compounds.
Ferralium 255: High-Strength Super Duplex Stainless Steel
Ferralium 255 is a super duplex stainless steel developed by Langley Alloys in the 1960s. It combines austenitic and ferritic phases to achieve high strength and excellent corrosion resistance. The alloy’s composition includes approximately 25.5% chromium, 5.5% nickel, 3.4% molybdenum, and 2.0% copper, contributing to its robust performance in aggressive environments.
Key Properties:
High Strength: Ferralium 255 exhibits a minimum yield strength of 586 N/mm², making it suitable for weight-critical and high-stress applications.
Superior Corrosion Resistance: The alloy’s resistance to pitting and crevice corrosion is enhanced by its high chromium and molybdenum content, as well as the presence of copper, which forms a protective layer at corrosion sites.
Applications:
Ferralium 255 is widely used in various industries, including:
Oil & Gas: Pumps, valves, wellhead and subsea equipment.
Marine Engineering: Propellers, shafts, rudders, seals, pumps, and valves.
Chemical Processing: Equipment in sulfuric acid, nitric acid, phosphoric acid, and PVC production.
Pollution Control: Scrubbers, precipitators, fans, and pumps.
Food Processing: Grain and vegetable processing plants, sugar cane centrifuges.
Alloy 625: Nickel-Based Superalloy for Extreme Conditions
Alloy 625 (UNS N06625) is a nickel-chromium-molybdenum alloy known for its exceptional resistance to oxidation and corrosion in a wide range of aggressive environments. Its composition includes approximately 61% nickel, 21.5% chromium, 9.0% molybdenum, and 3.6% niobium, contributing to its high strength and excellent weldability.
Key Properties:
High Temperature Strength: Alloy 625 maintains its mechanical properties at elevated temperatures, making it suitable for high-temperature applications.
Outstanding Corrosion Resistance: The alloy’s resistance to oxidation and corrosion is attributed to its high chromium and molybdenum content, as well as the presence of niobium, which enhances its resistance to carburization and oxidation.
Applications:
Alloy 625 is utilised in various industries, including:
Aerospace: Components such as turbine blades, seals, and exhaust systems.
Marine Engineering: Propellers, drive shafts, and thrusters.
Chemical Processing: Equipment in chemical reactors, heat exchangers, and pollution control systems.
Nuclear Power: Components in nuclear reactors and waste processing systems.
Comparison with Other Alloys in Harsh Environments
When selecting materials for applications in harsh environments, it’s essential to consider the specific conditions and requirements. Here’s a comparison of Ferralium 255 and Alloy 625 with other alloys commonly used in similar applications:
Ferralium 255 vs. Alloy 625: While both alloys offer excellent corrosion resistance, Ferralium 255 is a super duplex stainless steel with higher strength, making it suitable for structural applications. In contrast, Alloy 625 is a nickel-based superalloy with superior high-temperature strength, making it ideal for applications involving elevated temperatures.
Ferralium 255 vs. Alloy 20: Alloy 20 is a corrosion-resistant alloy with good resistance to sulphuric acid. However, Ferralium 255 offers higher strength and better resistance to pitting and crevice corrosion, making it more suitable for aggressive environments.
Alloy 625 vs. Hastelloy C-276: Both alloys offer excellent resistance to corrosion in harsh environments. However, Alloy 625 provides superior resistance to oxidation and carburisation at elevated temperatures, making it more suitable for high-temperature applications.
Conclusion
Ferralium 255 (UNS S32550) and Alloy 625 (AMS5666) (UNS N06625) are engineered to perform in some of the harshest conditions on earth. Their unique compositions and properties make them ideal choices for industries such as oil and gas, marine engineering, chemical processing, and aerospace. By understanding the specific requirements of each application and selecting the appropriate alloy, industries can ensure the longevity and reliability of their equipment in extreme environments.
Ready to Choose the Right Alloy for Your Project?
At Langley Alloys, we specialise in high-performance alloys like Ferralium 255 and Alloy 625, designed to meet the demands of challenging environments. Contact our expert team today to discuss your material needs and find the perfect solution for your application.
USA Sales: Email us at [email protected] or call +001 (281) 819 5588
UK Sales: Email us at [email protected] or call +44 (0)1782 610250
Let us help you select the ideal alloy to ensure durability and performance in your next project!
