Alloy 625 is a low carbon Ni-Cr-Nb alloy which shows excellent resistance to a variety of corrosion media
Alloy 625 is characterized by:
- Outstanding resistance to pitting, crevice corrosion, impingement corrosion and intergranular attacks
- Almost complete freedom from chloride-induced stress-corrosion cracking
- Good resistance to mineral acids, such as nitric, phosphoric, sulphuric and hydrochloric acids
- Good resistance to alkalis and organic acids
- Good mechanical properties
What is Nickel Alloy 625
Superalloys play a large role in many industries. These are materials that exhibit excellent mechanical strength, resistance to thermal creep, and resistance to issues like corrosion and oxidation. These alloys are used when high-temperature applications are required.
Nickel alloy 625 is an alloy that has been around since 1964, patented after extensive research into how a nickel-chromium molybdenum niobium alloy could work. The filing for the patent occurred in 1962, after almost a decade of research.
This alloy is like others in that category, with its ability to withstand high temperatures and corrosion. Developed for high-pressure steam lines in power plants, Nickel Alloy 625 has grown in its applications across many industries, with its resistance against harsh environments.
Alloy 625 has high strength properties, is creep-resistant, and is weld-able. It can withstand marine and dry environments, and also works well even in highly acidic situations. 625 alloy works in temperatures from cryogenic to 1800 F.
Because 625 alloy is so versatile, it is a valuable material in many industries. It is non-magnetic and spark resistant, adding to its attractive features.
The Power of Molybdenum in Alloy 625
Nickel Alloy 625 is unique because of the addition of molybdenum. Molybdenum adds strength and stiffening. This means that precipitation hardening treatments are not needed when working with nickel alloy 625.
The combination of Nickel, Chromium, and Molybdenum also ensures that alloy 625 is resistant to corrosion, oxidation, and carburization.
Where Nickel Alloy 625 Is Used
Because of its properties as a superalloy, 625 alloy is ideal for marine applications. It is used to make pumps and valves and other equipment used under high pressure. In the marine industry it works well for seawater components and can be used for specialized seawater equipment. You will find Alloy 625 in seawater parts like wire rope for mooring cables, propeller blades, submarine motors, submarine fittings, exhaust ducts on Navy boats, underwater cable sheathing, steam line bellows, fittings for underwater controls, and oceanographic equipment.
Alloy 625 is resistant to pitting and crevice corrosion and carries high corrosion fatigue strength. It has a high tensile strength and is resistant to chloride-ion stress-corrosion cracking, so it is perfect for saltwater use.
These properties are also ideal for nuclear applications, where Alloy 625 is used in reactor core and control rode components in water reactors. The high strength and resistance of 625 alloy is well suited to high temperatures. Alloy 625 is used in equipment for the production of super phosphoric acid, stress corrosion cracking resistant compensators, and furnace linings among other applications. It is a truly multipurpose alloy.
There are increasingly modern uses for Alloy 625 as well. Solar power stations are using this alloy for tubing, and Alloy 625 has even played a role in Tesla’s battery packs, helping to increase power output.
It also leaves a legacy as the genesis of another valuable alloy.
“As versatile and impressive as alloy 625 is, one of the truly amazing facts about its development history is that it was the seed for the development of alloy 718, the most successful age-hardenable nickel alloy ever developed,” says The Invention and Definition of Alloy 625. “Numerous other spin-off alloy compositions have been, and continue to be, developed. But even after over 30 years of existence, alloy 625 is still very much alive.”
A Weldable and Workable Alloy
The inclusion of a high molybdenum content initially led to concerns that Alloy 625 would not be suitable to welding, but studies have shown that it is, in fact, a great choice for welding. In fact, alloy 625 is used in weld overlay cladding to help with the strength and corrosion resistance of base materials.
Alloy 625 is easily joined with all conventional welding processes, from the soft or solution annealed condition. This alloy is able to be hot worked, cold worked, and machined. When machined, it should be done in the annealed condition, as it is prone to work hardening.
Product Forms of Alloy 625
Nickel Alloy 625 comes in various forms, including bar, wire, sheet, plate, forgings, pipe fittings, flanges, and tubes. It is known to be an alloy with excellent fabricability. It is this ease of fabricability that ensures Alloy 625 has a place across such a wide range of applications and industries.
With its ease of use, immense flexibility in terms of applications and industry, and long history in manufacturing and processing, it’s little wonder Alloy 625 is so well-used.
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