What is the difference between Inconel 625 and Inconel 725?
INCONEL 625 alloy contains small amounts of cobalt and silver, which are not present in INCONEL 725 alloy. INCONEL 725 alloy has a higher titanium content (1-1.7% compared to a maximum of 0.4% for INCONEL 625 alloy), with the remainder made up of iron, compared to a maximum of 5% for INCONEL 625 alloy.
What is Alloy 725?
Alloy 725 (UNS N07725), commonly known as Inconel 725, is a nickel-chromium-molybdenum-niobium alloy that is extremely corrosion resistant and can be age-hardened to achieve extreme strength.
What is the difference between Inconel 625 and INCONEL 825?
Inconel 625 is often used in sour gas service due to its good resistance to stress corrosion cracking and pitting, while Inconel 825 is often used in crude oil service due to its good corrosion resistance in sour environments.
What is 725 material?
725 alloy, commonly known as Inconel 725 (Inconel is a trademark of Special Metals Corp), is a nickel-chromium alloy with significant additions of molybdenum, niobium, and titanium. 725 alloy/Inconel 725 is available in the hot worked, annealed, and age hardened conditions.
Differences in composition
INCONEL Alloy 625 has such a wide range of desirable properties because of its unique composition. It is a high-nickel alloy, with a nickel content of at least 58%. In addition, it contains chromium (20-23%) and molybdenum (8-10%), as well as niobium (3.15-4.15%).
Niobium, combined with molybdenum, changes the atomic matrix of the alloy, giving it extremely high strength in the annealed state without the need for special strengthening heat treatments. The high levels of nickel and chromium together give the material excellent corrosion resistance, allowing it to withstand highly corrosive elements and environments.
INCONEL Alloy 725 shares many of the same constituent elements as Alloy 625-in fact, superficially, they are almost identical. It retains higher nickel (55-59%) and chromium (19-22.5%) contents, as well as molybdenum (7-9.50%). As a result, the material has similar corrosion resistance to INCONEL Alloy 625, making it suitable for a wide range of highly corrosive environments.
However, there are subtle differences in the overall composition of the two materials. INCONEL Alloy 625 contains small amounts of cobalt and silver, which are absent from INCONEL Alloy 725. INCONEL Alloy 725 has a higher titanium content (1-1.7% versus the 0.4% maximum for INCONEL Alloy 625), and the remainder is made up of iron, rather than the 5% maximum for INCONEL Alloy 625. These subtle additions and differences allow micro-precipitates to form during heat treatment, which greatly increase the strength of INCONEL Alloy 725.
Comparing strength
INCONEL Alloy 625 is a high-strength nickel alloy. As mentioned previously, this is due to its composition and the addition of niobium. The combination of niobium and molybdenum creates a hardening effect that eliminates the need for precipitation hardening. For many applications, the inherent high strength of this material is more than sufficient. It still outperforms many other nickel alloys in this area.
However, sometimes higher strength is required, but not at the expense of superior corrosion resistance. INCONEL Alloy 625 was originally introduced and sold as a solid solution strengthened alloy. It was discovered that it has age hardening properties and various tests were conducted to study the effects of this 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 - we call it INCONEL Alloy 725 (for more information, see this detailed report).
The strength of INCONEL Alloy 725 after age hardening is approximately twice that of INCONEL Alloy 625 after annealing. Because INCONEL Alloy 725 is strengthened by heat treatment rather than cold working, it retains high ductility and toughness. This strength can be imparted to large areas of non-uniform cross-section material that cannot be strengthened by cold working.
Gnee Steel is a supplier of Inconel 625 And Inconel 725, with products covering tubes, pipes, plates, strips, plates, round bars, flat bars, forged billets, hexagons, wire and extruded profiles. We work with steel mills to provide customers with 625 alloy, and its products meet or exceed many leading industry standards, including ASTM, ASME, SAE, AMS, ISO, DIN, EN and BS standards.
Gnee Steel stocks and sells Inconel 625 And Inconel 725 tubes, plates, strips, plates, round bars, flat bars, forged billets, hexagons, wire and extruded profiles. You are welcome to contact us for a quote at any time at ss@gneesteel.com
