Do You Know the Marvelous of Inconel 625?

┃ Overview

Inconel 625 (UNS N06625, Alloy 625, W.Nr. 2.4856) is a highly popular nickel-chromium alloy known for its exceptional properties, including high strength, excellent fabricability, and remarkable corrosion resistance. The strength of Inconel 625 is attributed to the reinforcing effect of molybdenum and niobium on its nickel-chromium matrix. As a result, it does not require precipitation hardening treatments. This unique combination of elements also provides superior resistance to various highly corrosive environments and high-temperature effects such as oxidation and carburization. Inconel 625 can effectively perform within a wide temperature range, from cryogenic temperatures up to 1800°F (982°C).

┃ Application

Sea-water Applications: wire rope for mooring cables, propeller blades for motor patrol gunboats, submarine auxiliary propulsion motors, submarine quick disconnect fittings, exhaust ducts for Navy utility boats, sheathing for undersea communication cables, submarine transducer controls, and steam-line bellows.

Aerospace Field: Aircraft ducting systems, engine exhaust systems, thrust-reverser systems, resistance welded honeycomb structures for housing engine controls, fuel and hydraulic line tubing, spray bars, bellows, turbine shroud rings, and heat-exchanger tubing in environmental control systems.

Chemical-processing Field: Bubble caps, tubing, reaction vessels, distillation columns, heat exchangers, transfer piping, and valves.

Nuclear Field: Reactor-core and control-rod components in nuclear water reactors

┃ Chemical Composition (%)

┃ Mechanical Property

┃Corrosion Resistance

The significant alloy composition of Inconel 625 imparts it with the ability to withstand a diverse range of highly corrosive environments. In mild conditions such as the atmosphere, fresh water, sea water, neutral salt, and alkaline media, the alloy exhibits minimal attack. In more severe corrosive environments, the presence of nickel and chromium grants the alloy resistance to oxidizing chemicals, while the combination of nickel and molybdenum provides resistance to nonoxidizing environments. Moreover, the high molybdenum content confers excellent resistance to pitting and crevice corrosion, while the elevated nickel content prevents chloride ion stress corrosion cracking. This comprehensive array of properties allows Alloy 625 to be utilized in a wide array of corrosive conditions.

┃Heat Treatment

Although Inconel 625 boasts outstanding strength, toughness, and resistance to high temperatures and corrosion, it can be susceptible to certain challenges such as cracks, distortions, and other issues that can affect its performance during the manufacturing process. To address these concerns and enhance the material's mechanical properties, heat treatment is employed. This process plays a crucial role in improving the alloy's durability and reliability, mitigating the aforementioned issues, and ensuring optimal performance in various applications.

┃ Heating and Pickling

Similar to other nickel-chromium and nickel-chromium-iron alloys, Inconel 625 has a tendency to develop a tightly bonded oxide or scale when exposed to heat, unless it has undergone bright annealing in a dry hydrogen or vacuum environment. To eliminate the oxide formation resulting from heating, it is generally recommended to subject the alloy to treatment in a fused-salt bath before pickling.

Following the fused-salt bath treatment, Inconel 625 can undergo pickling, which involves immersing the alloy in an acid solution to further eliminate any remaining oxides or impurities. Commonly used acids for pickling include hydrochloric acid or a mixture of nitric and hydrofluoric acids. It's important to note that the specific pickling processes may vary depending on the intended application and specific requirements.

┃ Hot and Cold Forming

Inconel 625 was specifically developed to maintain high strength at elevated temperatures and exhibits resistance to deformation during hot-working operations. However, the hot forming of this alloy requires robust equipment due to its high strength. When hot forming Alloy 625, it should be heated in a furnace with a temperature that is maintained at, but not exceeding, 2150°F (1177°C). To prevent the formation of a duplex grain structure, uniform reductions should be applied during the work process. It is recommended to achieve final minimum reductions of 15% to 20% for open-die work.

Inconel 625 can also be cold-formed using standard processes. Cold work can result in increased tensile properties, particularly for applications at moderate temperatures. Tensile strengths exceeding 300,000 psi (2068 MPa) with good ductility have been achieved in wire diameters ranging from 0.010 to 0.020 inches (0.254 to 0.508 mm) after 75% to 90% cold reduction.

┃ Machining

Inconel 625 can be machined using standard machining operations without significant difficulties. To achieve the best machinability, it is recommended to work with the alloy in the solution-treated condition. This condition refers to the state after the alloy has undergone a heat treatment process known as solution annealing, which helps optimize its mechanical properties and facilitate machining operations. By utilizing Inconel 625 in the solution-treated condition, machining can be performed more efficiently and effectively.

┃Welding

For optimal machining of Inconel 625, it is recommended to work with the alloy in the annealed condition. When machining, it is advisable to use low cutting speeds to minimize work-hardening and ensure better machinability. It is important to keep the cutting tool engaged at all times to prevent excessive work-hardening. A sufficient cut depth should be maintained to avoid contact with the previously formed work-hardened zone. By following these guidelines, the machining process for alloy 625 can be performed more effectively, reducing the risk of work-hardening and achieving better results.

┃ Product Forms

Ø Bar & Rod

Ø Plate & Sheet

Ø Coil & Strip

Ø Pipe & Tube

Ø Fitting: Flange, Tee, Elbow, Reducer etc.

Ø Forging: Ring, Shaft, Circle, Block etc.

┃ Note

Ronsco is a supplier with more than 27 years of experience in the special metal field, we always adheres to the business phiosophy of "customer-centered", tries its best to meet the requirements of customers and pursues win-win cooperation with customers. Are you looking for special metal products one-stop supplier! Contact Us Now! Email: marketing@ronsteel.com