INCONEL 625, Alloy 625

N06625 tubing, Alloy 625 plates

INCONEL nickel-chromium alloy 625 (UNS N06625/W.Nr. 2.4856) is used for its high strength, excellent fabricability (including joining), and outstanding corrosion resistance. Service temperatures range from cryogenic to 1800°F (982°C). The composition is shown in the Table below.

The strength of INCONEL alloy 625 is derived from the stiffening effect of molybdenum and niobium on its nickel-chromium matrix; thus precipitation hardening treatments are not required. This combination of elements also is responsible for superior resistance to a wide range of corrosive environments of unusual severity as well as to high-temperature effects such as oxidation and carburization.

The properties of INCONEL alloy 625 that make it an excellent choice for sea-water applications are freedom from local attack (pitting and crevice corrosion), high corrosion-fatigue strength, high tensile strength, and resistance to chloride-ion stress-corrosion cracking. It is used as 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, and sheathing for undersea communication cables, submarine transducer controls, and steam-line bellows. Potential applications are springs, seals, bellows for submerged controls, electrical cable connectors, fasteners, flexure devices, and oceanographic instrument components.

High tensile, creep, and rupture strength; outstanding fatigue and thermal-fatigue strength; oxidation resistance; and excellent weldability and braze ability are the properties of INCONEL alloy 625 that make it interesting to the aerospace field. It is being used in such applications as 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. It is also suitable for combustion system transition liners, turbine seals, compressor vanes, and thrust-chamber tubing for rockets.

The outstanding and versatile corrosion resistance of INCONEL alloy 625 under a wide range of temperatures and pressures is a primary reason for its wide acceptance in the chemical processing field. Because of its ease of fabrication, it is made into a variety of components for plant equipment. Its high strength enables it to be used, for example, in thinner-walled vessels or tubing than possible with other materials, thus improving heat transfer and saving weight. Some applications requiring the combination of strength and corrosion resistance offered by INCONEL alloy 625 are bubble caps, tubing, reaction vessels, distillation columns, heat exchangers, transfer piping, and valves.

In the nuclear field, INCONEL alloy 625 may be used for reactor-core and control-rod components in nuclear water reactors. The material can be selected because of its high strength, excellent uniform corrosion resistance, resistance to stress cracking and excellent pitting resistance in 500°-600°F (260-316°C) water. Alloy 625 is also being considered in advanced reactor concepts because of its high allowable design strength at elevated temperatures, especially between 1200°-1400°F (649-760°C).

The properties given in this bulletin, results of extensive testing, are typical of the alloy but should not be used for specification purposes. Applicable specifications appear in the last section of this publication.

Inconel 625 Available Forms and Specifications

INCONEL alloy is designated as UNS N06625, Werkstoff Number 2.4856 and ISO NW6625 and is listed in NACE MR-01-75. It is available in all standard mill forms including rod, bar, wire, and wire rod, plate, sheet, strip, shapes, tubular products, and forging stock. Full information on available products may be obtained from the offices listed on the back cover:

Rod, Bar, Wire and Forging Stock – ASTM B 446/ASME SB 446 (Rod & Bar), ASTM B 564/ASME SB 564 (Forgings), SAE/AMS 5666 (Bar, Forgings, & Rings), SAE/AMS 5837 (Wire), ISO 9723 (Rod & Bar), ISO 9724 (Wire), ISO 9725 (Forgings), VdTÜV 499 (Rod & Bar), BS 3076NA21 (Rod & Bar), EN 10095 (Rod, Bar, & Sections), DIN 17752 (Rod & Bar), ASME Code Case 1935 (Rod, Bar, & Forgings), DIN 17754 (forgings), DIN 17753 (Wire).

Plate, Sheet and Strip – ASTM B 443/ASTM SB 443 (Plate, Sheet & Strip), SAE/AMS 5599 & 5869 & MAM 5599 (Plate, Sheet & Strip), ISO 6208 (Plate, Sheet & Strip), VdTÜV 499 (Plate, Sheet & Strip), BS 3072NA21 (Plate & Sheet), EN 10095 (Plate, Sheet & Strip), DIN 17750 (Plate, Sheet & Strip), ASME Code Case 1935.

Pipe & Tube – ASTM B 444/B 829 & ASME SB 444/SB 829 (Seamless Pipe & Tube), ASTM B704/B 751 & ASME SB 704/SB 751 (Welded Tube), ASTM B705/B 775 & ASME SB 705/SB 775 (Welded Pipe), ISO 6207 (Tube), SAE/AMS 5581 (Seamless & Welded Tube), VdTÜV 499 (Tube), BS 3074NA21 (Seamless Pipe & Tube), DIN 17751 (Tube), ASME Code Case 1935.

Other Product Forms – ASTM B 366/ASME SB 366 (Fittings), ISO 4955A (Heat Resisting Steels & Alloys), DIN 17744 (Chemical composition of all product forms).

Inconel 625 Chemical Composition, %

Ni Cr Mo Nb Fe C Ti Mn Si S P
58.0 min 20~23 8~ 10 3.15 – 4.15 5.0 max 0.1 max 0.4 max 0.50 max 0.50 max 0.015 max 0.015 max

Inconel 625 Mechanical Properties

Density,g/c㎡ 8.44
Melting range,℃ 1290-1350
Tensile strength, min, Mpa 760
Yield strength, 0.2% offset, min, Mpa 345
Elongation,% 25
Hardness, HB, min 220


Alloy 625 through softening and annealing is widely used in the chemical process industry and on Offshore & marine occasions or bearing high mechanical stress. It’s highly resistant to corrosion and its high strength makes it can be used as a thinner structural part. The typical applications are:

  1. Components of an organic chemical process containing chlorides, especially in the use of acid chloride catalysts
  2. Digesters and bleaching tanks for the pulp and paper industries;
  3. Absorption tower, reheater, flue gas inlet baffle, fan (moisture), mixer, flow guide plate, flue gas flue gas desulfurization system, etc;
  4. Equipment and components used in the manufacture of acidic gas environments;
  5. Acetic acid and acetic anhydride reaction generator;
  6. Sulfuric acid condenser.

LKALLOY is a leading supplier of Inconel Alloy 625 and other high-quality special metal alloys with decades of experience and extensive specifications. To buy or learn more about Alloy 625, contact us now.