What is INCONEL 725 used for?
We take an in-depth look at these two popular high-performance nickel alloys and compare their specifications and applications.
When you're looking for quality materials for your next project, high-performance nickel alloys may be just what you're looking for. However, there are a variety of grades available in the INCONEL range, any of which may suit your requirements and needs.
The flagship INCONEL alloy is INCONEL Alloy 625, one of the most versatile materials ever created. With its excellent corrosion resistance and high strength, it is suitable for a variety of applications in various industries. It is a very popular material choice and will solve many material problems for design engineers. That it has been doing this for over 50 years and is still widely used is a testament to its quality.
However, if high strength is a priority, INCONEL Alloy 725 may be more suitable. It is similar to INCONEL alloy 625, especially in terms of corrosion resistance. However, there are significant differences between the two, which may affect the decision of which one to use.
To help you understand the differences and similarities between these two special materials, we've compared their key features and properties.
Differences in ingredients
INCONEL 625 alloy is able to offer such a wide range of desirable properties due to its unique composition. It is a nickel-heavy alloy with a mixture containing at least 58% nickel. It also contains chromium (20-23%) and molybdenum (8-10%), with added niobium (3.15-4.15%).
Niobium combines with molybdenum and twists the atomic matrix of the alloy, imparting particularly high strength in the annealed condition without the need for a specific strengthening heat treatment. The large amounts of nickel and chromium combine to give the material incredible corrosion resistance, able to withstand highly corrosive elements and environments.
INCONEL 725 alloy shares many of the same constituent elements – in fact, superficially, they are nearly identical. It retains significant amounts of nickel (55-59%) and chromium (19-22.5%), as well as molybdenum (7-9.50%). As a result, the material has similar corrosion resistance to INCONEL 625 alloy, making it suitable for use in a variety of highly corrosive environments.
However, there are subtle differences in the overall composition of the two materials. INCONEL 625 alloy contains small amounts of cobalt and silver, while these materials are not present in the INCONEL 725 alloy blend. INCONEL 725 alloy contains a higher content of titanium (1-1.7% compared to a maximum of 0.4% in INCONEL alloy 625) and iron to make up the balance, rather than the 5% maximum content of INCONEL alloy 625. These small additions and differences allow the formation of microprecipitates during heat treatment, resulting in a significant increase in the strength values of INCONEL Alloy 725.
Strength comparison
INCONEL 625 alloy is a high strength nickel alloy. As mentioned before, this depends on its composition and the effect of adding niobium. A mixture of niobium and molybdenum produces a hardening effect without the need for precipitation hardening. For many applications, the material's inherently high strength is sufficient. It still outperforms many other nickel alloys in this area.
However, sometimes greater strength is required without sacrificing excellent corrosion resistance. INCONEL Alloy 625 is introduced and marketed as a solid solution strengthened alloy. It was found to be age-hardenable and it was subjected to various tests to study its effects over time. It was found that the addition of titanium significantly improved the age hardening response. This led to the creation of a new alloy – which we call INCONEL Alloy 725 (learn more in this detailed report).
Age-hardened INCONEL Alloy 725 is approximately twice as strong as annealed INCONEL Alloy 625. Because INCONEL 725 alloy is strengthened by heat treatment rather than cold working, it retains high ductility and toughness. This strength can be imparted to large, uneven portions of material that cannot be strengthened by cold working.
different applications
The choice of material often depends on the alloy's intended end application.
Due to its versatility, INCONEL 625 alloy is used in a wide variety of industries. For example, it is often used in seawater applications because it resists localized corrosion such as pitting and crevice corrosion. It also resists chloride ion stress corrosion cracking. As such, applications include propeller blades for gunboats, propulsion motors for submarines, exhaust pipes for naval work vessels, and sheathing for undersea communications cables.
It is also the material of choice for the aerospace industry, where its high strength, high fatigue resistance and excellent weldability are ideal assets. This includes use in aircraft ductwork, engine exhaust systems and fuel lines. Other industrial applications include nuclear reactor components and extensive use in chemical processing plants.
INCONEL 725 alloy is also widely used in many industries, but when extremely high strength is required, INCONEL 725 alloy should be chosen instead of INCONEL alloy 625. For example, in the collection of sour gases, where excellent resistance to highly corrosive media is required, INCONEL alloy 725 is used in the manufacture of hangers, landing joints, side bag mandrels and polished hole sockets, among others.
Like INCONEL 625 alloy, INCONEL 725 alloy is also used in the marine industry. It is a good choice for products such as high-strength fasteners that require extra strength without sacrificing resistance to corrosion, pitting or crevice attack.
If you are interested in learning more about INCONEL Alloy 625 or INCONEL Alloy 725 and the rest of our product lines, please contact an experienced member of our sales team today.
