What is the strongest Inconel alloy?

Extremely high strength and toughness are desirable qualities in industrial applications. We explore the strength properties of INCONEL Alloy 725, an age-hardenable material with excellent corrosion resistance
Some industrial applications require the highest strength materials to withstand harsh environments. INCONEL Alloy 725 is one such material that achieves extremely high strength through precipitation hardening.

This heat treatment increases the yield strength, producing a material that is particularly tough and strong even at high temperatures. In this age-hardening condition, INCONEL Alloy 725 is one of the strongest superalloys in the GNEE product range and combines ductility and toughness.

In addition to its heat treatment, INCONEL 725 alloy is strong due to its balanced elemental composition. It is a nickel-chromium grade but also contains significant amounts of molybdenum. This important chemical element gives nickel alloys excellent strength and mechanical stability, which is why it is widely used.
The alloy also includes aluminum and titanium, the latter of which has the highest strength-to-density ratio of any metallic element. Both of these additions help impart the desired strength qualities.

Inconel 725 VS 625
INCONEL Alloy 725 is comparable in many ways to the popular INCONEL Alloy 625, another superalloy known for its high strength and versatility. Both grades offer similar levels of excellent corrosion resistance, allowing them to be used in some of the harshest environments. This corrosion resistance helps INCONEL 725 alloy maintain its renowned strength and is highly resistant to hydrogen embrittlement and stress corrosion cracking – two factors that can negatively impact the material’s continued strength.

The addition of nickel and chromium provides resistance to reducing and oxidizing environments, while the aforementioned molybdenum enhances its resistance to reducing media and provides some protection against pitting and crevice corrosion.

INCONEL Alloy 725 is developed from INCONEL Alloy 625, building on its already impressive foundation and adding elements and treatments to enhance its mechanical properties to provide even greater strength. Therefore, it is approximately twice as strong as annealed INCONEL Alloy 625.

Industrial applications
Materials with such high levels of corrosion resistance, strength, ductility and toughness can be used in many different situations. It is commonly used in tubing hangars, landing joints, side bag mandrels, polished bore sockets and high strength fasteners.

One of its primary uses is in the sour gas industry, where it exhibits corrosion resistance to the effects of hydrogen sulfide, chloride and carbon dioxide, maintaining its strength under these toxic conditions. It is also widely used in marine applications as it resists pitting and crevice attacks in seawater.

INCONEL 725 alloy is also available in a higher strength version, the 725HS alloy. The material offers the same excellent corrosion resistance as its base material, but is 2.3 times stronger than annealed INCONEL Alloy 625 and has a yield strength approximately 20ksi higher than standard INCONEL Alloy 725. This is achieved by optimizing the age hardening process and grain refinement. The material can be used for components in ship construction, where seawater resistance is crucial but extreme strength is also required.

Contact a member of our team to learn more about INCONEL 725 alloy.