Nickel Alloys Inconel Alloy 625 N06625
Austral Wright Speciality Metals

 Product Data Sheet   Nickel Alloys

Inconel® Alloy625™   UNS-N0776625

Inconel® Alloy 625™ is a nickel chromium molybdenum alloy with high strength at elevated temperatures, combined with outstanding corrosion resistance. It has the best all-round combination of strength and corrosion resistance of the Inconel family of alloys. It is pre-qualified for use in pressure vessels up to 815°C. Inconel 625LCF is a special quality of the alloy for use in bellows.

Chemical Composition

ASTM B446 – Bar

Element Inconel® 625 Inconel® 625LCF
Nickel
58.0 min 58.0 min
Chromium
20.0-23.0 20.0-23.0
Molybdenum
8.0-10.0 8.0-10.0
Niobium + Tantalum
3.15-4.15 3.15-4.15
Iron
5.0 max 5.0 max
Cobalt (if determined)
1.0 max 1.0 max
Manganese
0.50 max 0.50 max
Carbon
0.10 max 0.03 max
Nitrogen
0.02 max
Silicon
0.15 max 0.15 max
Phosphorus
0.015 max 0.015 max
Sulphur
0.015 max 0.015 max
Aluminium
0.40 max 0.40 max
Titanium
0.40 max 0.40 max

Specified Minimum Mechanical Properties

ASTM B446 – Bar

0.2% Proof Stress
Tensile Strength
Elongation
MPa
MPa
%
Grade 1 (Annealed) Up To 102mm 415 830 30
103 to 254mm 345 760 25
Grade 2 (Solution Annealed) All 275 690 30

Grade 1 – Annealed at 870°C minimum

Grade 2 – Solution Annealed at 1090°C (min), with or without stabilise anneal at 980°C (min) for sensitisation resistance.

Typical Applications

Chemical plant, bellows, submerged marine components, weld overlays, power station scrubber systems, general corrosion applications for aggressive environments, combustion and ducting systems, fuel nozzles, after burners, aerospace components.

Description

Inconel 625 is a nickel chromium molybdenum solid solution strengthened high strength alloy, which retains strength to high temperatures. It is used from cryogenic temperatures to 980°C. Fatigue strength is outstanding, particularly as the bellows grade, Inconel 625LCF, where carbon, silicon and nitrogen are controlled to low levels. The alloys have good oxidation resistance and resist corrosion by many corrosive media. When exposed to high temperature for long periods, Inconel 625 will age harden due to the niobium, titanium and aluminium additions. When aged there is an increase in strength and some loss of ductility and toughness.

Availability

Austral Wright Metals can supply Inconel 625 as plate, sheet and strip, rod and bar, seamless and welded tube and pipe, welding fittings, forgings and forging billet. Inconel 625LCF is available as annealed sheet and strip from 0.13 mm to 2.54 mm thick, up to 1219 mm wide.

Nickel Alloys Inconel Alloy 625 N06625 Temperature Nickel Alloys Inconel Alloy 625 N06625 Stress
High temperature tensile properties of annealed Inconel® Alloy 625™ sheet. Low cycle fatigue strength of Inconel® Alloy 625™ and Inconel® 625LCF™ at 480 – 650°C.

Pressure Vessels

AS1210 prequalifies Inconel 625 up to 625°C as flat products, and 650°C as bar and forgings. ASME Boiler & Pressure Vessel Code, Section VIII (Code Case 1409-5) allows annealed material to be used to 650°C, solution treated to 815°C.

Corrosion Resistance

Inconel 625 has a corrosion resistance to many environments. In mild environments such as atmosphere, fresh water and sea water, neutral salts and alkaline media there is almost no attack. In more aggressive media nickel and chromium resist oxidising attack, while nickel and molybdenum resist reducing environments. Molybdenum provides exceptional resistance to pitting and crevice corrosion, and niobium stabilises against sensitisation and intergranular corrosion. The nickel content makes Inconel 625 essentially free from chloride ion stress corrosion cracking. Inconel 625 also has excellent corrosion fatigue properties. Please consult Austral Wright Metals for specific advice on your application.

Corrosion Rates (mm/year) in a Municipal Waste Incinerator

at 650-700°C after 2050 hours and 6750 hours

Alloy 2050 hours 6750 hours
Inconel 625 7 13
Incoloy 800 35 Destroyed
Incoloy 825 127 Destroyed
Alloy 2050 hours 6750 hours
SS310 48 89
SS316 71 Destroyed
SS446 82 54

Equivalent Specifications

Country Body Grade
USA UNS N06625
France AFNOR NC 22 D Nb
GB BS NA21
Germany DIN 2.3856

Fabrication

Inconel 625 was developed for hot strength, so resists hot working. It is ductile and can be readily hot worked with high forces. The alloy can also be cold formed with heavy forces. Intermediate annealing may be needed.

Machinability

Inconel 625 is difficult to machine (class D-2). Heavy machines, sharp tools, slow speeds and deep uninterrupted cuts to remove the work hardened layer are needed.

Weldability

Inconel 625 is readily welded by GMAW (MIG), GTAW (TIG), SMAW (manual) and SAW processes. Preheat, post heat and post weld heat treatment are not required. The area around the weld must be clean to prevent contamination of the weld pool. Argon shielding gas is used.

Normal Service Higher Strength Best Corrosion Resistance
Welding Electrode Inconel WE 112 N/A Inco Weld WE 686CPT
Filler Metal Inconel FM 625 Inco Weld FM725NDUR Inco Weld FM 686CPT
Flux Cored Wire Inco Cored 625DH N/A N/A

Heat Treatment

Inconel 625 is annealed at 925–1040°C, cooling rate not critical. Solution anneal at 1090–1200°C. Stress relief, if required, is at 590–760°C, or up to 870°C for complete relief.

Physical Constants and Thermal Properties

Inconel 625 and 625LCF, Annealed

Property
Metric Units
Density
8,440 k g/m³ @ 20°C
Melting Point
1290-1350°C
Electrical Resistivity
1.29 micro-ohm . m @ 20°C
Electrical Conductivity
1.3 % IACS @ 20°C
Specific Heat
410 J/kg . °C @ 20°C
Mean Coefficient of Expansion
12.8 x 10-6 / °C @ 20°C
Thermal Conductivity
9.8 W / m . °C @ 20°C
Curie Temperature
<-196 @ 20°C
Annealed
Modulus of Elasticity
Tension
208 GPa @ 20°C
Torsion
81.4 GPa @ 20°C
Poisson’s Ratio
0.278 @ 20°C
Solution Treated
Modulus of Elasticity
Tension
205 GPa @ 20°C
Torsion
77.9 GPa @ 20°C
Poisson’s Ratio
0.312 @ 20°C

ASTM Product Specifications

Specification Title
B366 Factory Made Wrought Nickel and Nickel Alloy Fittings
B443 Nickel Chromium Molybdenum Columbium Alloy (UNS N06625) Plate, Sheet and Strip
B444 Nickel Chromium Molybdenum Columbium Alloys (UNS N06625) Pipe and Tube
B446 Nickel Chromium Molybdenum Columbium Alloys (UNS N06625) Rod and Bar
B564 Nickel Alloy Forgings
B704 Welded UNS N06625 and UNS N08825 Alloy Tubes
B705 Nickel Alloy (UNS N06625 and N08825) Welded Pipe
B751 General Requirements for Nickel and Nickel Alloy Welded tube

Note: The Element Niobium is called Columbium in USA

 

The technical advice and recommendations made in this Product Data Sheet should not be relied or acted upon without conducting your own further investigations, including corrosion exposure tests where needed. Please consult current editions of standards for design properties. Austral Wright Metals assumes no liability in connection with the information in this Product Data Sheet. Austral Wright Metals supplies a comprehensive range of stainless steels, copper alloys, nickel alloys and other high performance metals for challenging service conditions. Our engineers and metallurgists will be pleased to provide further data and applications advice.

 

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