What is Inconel 725 used for?
Inconel 725 alloy has extremely high strength and corrosion resistance, making it ideal for a variety of high-performance applications in harsh environments, including oil and gas equipment components, marine and offshore components, aerospace, pollution control, and chemical processing industries.
Differences between Inconel 725 and Inconel 625
Inconel 725 (alloy 725, UNS N07725) has a nearly identical composition to Inconel 625 (alloy 625, UNS N06625, 2.4856), resulting in very similar corrosion resistance and physical properties. However, 725 alloy has significantly higher strength due to its precipitation strengthening properties.
The strength of Inconel 625 alloy increases after heat treatment, and further additions of titanium further enhance this phenomenon. These trace additions promote the formation of microscopic precipitates after the alloy has been heat treated for a long time, giving it a yield strength twice that of Inconel 625 alloy.
Because Inconel 725 derives its strength from heat treatment rather than cold working, its ductility and toughness remain high. As a result, the smallest diameter Inconel 725 is most often used in fastener production, while slightly larger Inconel 725 is used for auxiliary fixing. Gnee Steel has a large inventory of 725 alloy, ranging from 1 inch (25.4 mm) to 4 inches (101.6 mm) in diameter, and larger diameters are also available to order.
Properties and Applications of Inconel 725 Alloy
With its high strength and resistance to seawater corrosion, Inconel 725 alloy is ideal for marine components in naval and submarine systems. It has a pitting resistance equivalent value (PREN) of >45, making it extremely resistant to pitting and crevice corrosion. It can be considered an upgrade of Monel K-500 (alloy K-500, 2.4375), which has been widely used in offshore engineering for many years.
The use of this grade of alloy in conjunction with less corrosion resistant metals by agencies such as the US Navy has meant that cathodic protection has been used to extend the service life of the alloy steel. However, occasional failures of K-500 alloy products have been associated with hydrogen embrittlement and accelerated corrosion by galvanic action with more precious metals.
Inconel 725 overcomes this risk and offers increased strength and toughness. It has been used as a control shaft for sliding surfaces and other exposed structural elements.
Inconel 725 development
Inconel 725 is an improvement on Inconel 718 and Monel K-500 for certain oilfield applications. The presence of hydrogen sulfide, carbon dioxide and chlorides at high pressures and temperatures can cause extremely severe corrosion in such sour wells. Inconel 725 has a higher corrosion resistance and is therefore widely used in applications such as tubing hangers, mandrels and casing, although these parts are usually forged rather than machined from our bar stock.
