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UNS N06625 NC22DNb W.Nr.2.4856 Inconel alloy 625 Nickel-based Alloy

Inconel alloy 625 Nickel-based Alloy inconel alloy 625 UNS N06625 NC22DNb W.Nr.2.4856 Inconel alloy 625 Nickel-based Alloy Inconel alloy 625 Nickel based Alloy

Inconel alloy 625 Nickel-based Alloy


Inconel Alloy 625 is an austenitic nickelchromium-molybdenum-niobium alloy possessing a rare combination of outstanding corrosion resistance coupled with high strength from cryogenic temperatures to 1800°F(982°C).
The strength of Inconel Alloy 625 is derived from the solid-solution hardening of the nickel-chromium
matrix by the presence of molybdenum and niobium. Therefore, precipitation-hardening treatments
are not required.
The chemical composition of Inconel Alloy 625 is also responsible for its outstanding corrosion resistance in a variety of severe operating environments along with resistance to oxidation and carburization in high temperature service. The alloy is resistant to pitting, crevice corrosion, impingement corrosion, intergranular attack and is almost immune to chloride stress corrosion cracking.
Inconel Alloy 625 can be easily welded and processed by standard shop fabrication practices.


• Aerospace Components: bellows and expansion joints, ducting systems, jet engine exhaust systems, engine thrust-reversers, turbine shroud rings
• Air Pollution Control: chimney liners, dampers, flue gas desulfurization (FGD) components
• Chemical Processing: equipment handling both oxidizing and reducing acids, super-phosphoric acid production
• Marine Service: steam line bellows, Navy ship exhaust systems, submarine auxiliary propulsion systems
• Nuclear Industry: reactor core and control rod components, waste reprocessing equipment
• Offshore Oil and Gas Production: waste flare gas stacks, piping systems, riser sheathing, sour gas piping and tubing
• Petroleum Refining: waste flare gas stacks
• Waste Treatment: waste incineration components

Size Range:
Plate and Sheet: Thickness: 0.016″-3.00″, Width: 20″-48″
Round Bar: 1/4″ Diameter to 12″ Diameter
Tube (welded & seamless): Outer Diameter: 1/16″-3″, Wall Thickness: 0.010″-0.250″,
Length: 17’/24′ FT R/L
Pipe: 1/4″ sch 10 to 16″ sch 80
Wire: 0.1mm-20mm

Quality Standard:
ASTM B443 Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNSN06625) and Nickel-Chromium-Molybdenum-Silicon Alloy(UNS N06219)* Plate, Sheet, and Strip
ASTM B446 Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNSN06625) rod and bar
AMS 5666 Nickel Alloy, Corrosion and Heat-Resistant, Bars, Forgings, Extrusions, and Rings, 62Ni – 21.5Cr – 9.0Mo – 3
AMS 5599 Nickel Alloy, Corrosion and Heat Resistant Sheet Strip and Plate 62Ni-21.5Cr-9.0Mo-3.7Cb (Nb) Solution Heat Treated
AMS 5879
BS EN ISO 15156-3 Petroleum and Natural Gas industries materials for use in H2s containling environments in oil and gas production part3 cracking resistant CRAs (corrosion resistant alloys) and other alloys

All Grades Comparison

W.Nr.2.4856 N06625 NC22DNb

Chemical Composition(%)

C Si Mn P S Cr Ni Cb+Ta Co Mo Fe Al Ti
0.1 max 0.5 max 0.5 max 0.015 max 0.015 max 20.0-23.0 58.0 min 3.15-4.15 1.0 max 8.0-10.0 5.0 max 0.4 max 0.4 max

Mechanical Properties

Form and Delivery Condition Tensile Strength Rm (Mpa) Yield Strength Rp0.2 (Mpa) Elongation % in 2″ (50.8 mm) Reduction Of Area (%) Hardness (HBW)
Rod, Bar and Plate (As Rolled) 827-1103 414-758 60-30 60-40 175-240
Rod, Bar and Plate (Annealed) 827-1034 414-655 60-30 60-40 145-220
Rod, Bar and Plate (Solution-Treated) 724-896 290-414 65-40 90-60 116-194
Sheet and Strip (Annealed) 827-1034 414-621 55-30 / 145-240
Tube and Pipe, Cold Drawn (Annealed) 827-965 414-517 55-30 / /
Tube and Pipe, Cold Drawn (Solution-Treated) 689-827 276-414 60-40 / /


Sodium hydride baths are necessary to descale this alloy. After the sodium hydride treatment, the material should be immersed in a sulfuric acid bath 165°F (74°C) for approximately 3 minutes. A 25-minute immersion in a nitric-hydrofluoric bath 145°F (63°C) is then necessary. Rinse. Sulfuric solution: 16% by weight, H2SO4. Nitric solution: 8% HNO3 by weight and 3% HF by weight. Acid etching for macro-inspection-expose material electrolytically to a 3-to-1 HCl to HNO3 solution, saturated with CuCl2 at a current density of 0.645 amp/in² (25.4 A/m)

Heat Treatment:

Inconel Alloy 625 has three basic heat treatments:
(1)High Solution Anneal – 2000/2200°F (1093/1204°C), air quench or faster.
(2)Low Solution Anneal – 1700/1900°F (927/1038°C), air quench or faster.
(3)Stress Relieve – 1650°F (899°C), air quench.
The time at the above temperatures depends on volume and section thickness. Strip, for example, would require shorter times than large sections. Temperatures for treatments No. 1 and 2 are generally held for 1/2 to 1 hour, 1 to 4 hours for treatment No. 3.

Treatment No. 1 is not commonly used for applications below 1500°F (816°C). It is generally used above 1500°F and where resistance to creep is important. The high solution anneal is also used to develop the maximum softness for mild processing operations such as cold rolling or drawing.
Treatment No. 2 is the used treatment and develops an optimum combination of tensile and rupture properties from ambient temperatures to 1900°F (1038°C). Ductility and toughness at cryogenic temperatures are also very good.

Treatment No. 3 is recommended for application below 1200°F (649°C) when maximum fatigue, hardness, tensile and yield strength properties are desired. Ductility and toughness at cryogenic temperatures are excellent. When a fine grain size is desired for fatigue, tensile and yield strengths up to 1500°F (816°C), treatment No. 3 is sometimes used.

Oxidation Resistance:

The oxidation and scaling resistance of Inconel Alloy 625 is superior to a number of heat resistant austenitic stainless steels such as 304, 309, 310 and 347 up to 1800°F (982°C) and under cyclic heating and cooling conditions. Above 1800°F (982°C), scaling can become a restrictive factor in service.

Corrosion Resistance:

The highly alloyed chemical composition of Inconel Alloy 625 imparts outstanding corrosion resistance in a variety of severely corrosive environments. The alloy is virtually immune to attack in mild conditions such as the atmosphere, fresh and sea water, neutral salts and alkaline solutions. Nickel and chromium provide resistance to oxidizing solutions and the combination of nickel and molybdenum supply resistance in non-oxidizing environments. Molybdenum also makes Alloy 625 resistant to pitting and crevice corrosion, while niobium acts as a stabilizer during welding to prevent intergranular cracking. The high nickel content of Inconel Alloy 625 makes it virtually immune to chloride stress
corrosion cracking.
The alloy resists attack by mineral acids such as hydrochloric, nitric, phosphoric and sulfuric, and to alkalis and organic acids in both oxidizing and reducing conditions.

Fabrication Data:

Inconel Alloy 625 can be easily welded and processed by standard shop fabrication practices, however
because the high strength of the alloy, it resists deformation at hotworking temperatures.
Hot Forming
The hot-working temperature range for Alloy 625 is 1650–2150°F (900–1177°C). Heavy working needs to occur as close to 2150°F (1177°C) as possible, while lighter working can take place down to 1700°F (927°C).
Hot-working should occur in uniform reductions to prevent duplex grain structure
Cold Forming
Inconel Alloy 625 can be cold-formed by the standard shop fabrication practices. The alloy should be in the annealed condition. Work hardening rates are higher than the austenitic stainless steels.
Inconel Alloy 625 can be readily welded by most standard processes including GTAW (TIG), PLASMA,
GMAW (MIG/MAG), SAW and SMAW (MMA). A post weld heat treatment is not necessary. Brushing with a
stainless steel wire brush after welding will remove the heat tint and produce a surface area that does not require additional pickling.
Inconel Alloy 625 should preferably be machined in the annealed condition.
Since Alloy 625 is prone to workhardening, only low cutting speeds should be used and the cutting tool
should be engaged at all times. Adequate cut depth is necessary to assure avoiding contact with the
previously formed work-hardened zone.

Mill′s test certificate:

EN 10204/3.1 with all relevant data reg. chem. composition, mech. properties and results of testing.