Alloy 725 / Inconel 725®

General Characteristics

Alloy 725 (W-Nr. 2.4857; UNS N07725) Alloy 725 is a nickel-chromium-based superalloy, enriched with significant additions of molybdenum, niobium, and titanium. This alloy stands out for its extremely high mechanical strength and excellent corrosion resistance, even in the most aggressive environments.
In addition, Alloy 725 is available in various conditions: hot-worked, annealed, or age-hardened. In its hardened form, it reaches nearly twice the strength of annealed Alloy 625, due to the precipitation of the ϒ” phase during controlled heat treatment.

Furthermore, since thermal aging is responsible for hardening (rather than cold plastic deformation), the alloy maintains remarkable ductility and toughness, making it ideal for large or complex-shaped components that are difficult to harden by other means.

Corrosion resistance

Alloy 725 offers corrosion resistance comparable to Alloy 625 and is effective in:

• Reducing environments (sulfuric and phosphoric acids) – thanks to molybdenum
• Oxidizing environments (nitric acid) – due to the presence of chromium
• Prevention of intergranular corrosion – enabled by titanium

Additionally, its high nickel content ensures exceptional resistance to stress corrosion cracking, and the overall balance of alloying elements provides robust protection against both general corrosion and pitting corrosion.

Typical Applications

Thanks to its properties, Alloy 725 is widely used in:

• Equipment for severely corrosive environments
• Fasteners and anchors for marine applications
• Components for the chemical industry
• Rods and valves used in oil and gas wells, including those with H₂S, CO₂, and chlorides

It is important to note that this alloy is approved under NACE MR0175, making it fully compliant with oil and gas industry applications.