What is Inconel 625?
Inconel 625 is a nickel-chromium-molybdenum-niobium superalloy with an austenitic face-centred-cubic matrix. It contains a minimum of 58 % nickel, 20.0–23.0 % chromium, 8.0–10.0 % molybdenum and 3.15–4.15 % niobium plus tantalum.
Molybdenum and niobium stiffen the nickel-chromium matrix by solid-solution strengthening, which is what makes 625 unusual: it reaches roughly 827 MPa tensile strength in the annealed condition with no age-hardening heat treatment at all. That also means niobium stabilisation removes the need for post-weld heat treatment to restore corrosion resistance, which is a real cost advantage over 316L in fabricated assemblies.
The same chemistry gives the alloy resistance to pitting, crevice corrosion, chloride stress-corrosion cracking, intergranular attack and oxidation, usable from cryogenic temperatures up to about 982 °C (1800 °F). Its calculated pitting resistance equivalent number is around 51, which is why it is a standard choice for seawater, sour gas and flue-gas service.
Forging note. Inconel 625 work-hardens rapidly, both under the hammer and under the cutting tool. Open-die forging it well means reheating often to stay inside the working range, controlling the finishing temperature, and machining at low cutting speeds with rigid tooling. This is why 625 forgings are quoted differently from stainless forgings of the same shape.
Inconel 625 forgings we produce
Jiangyin Jiangnan Metal Co., Ltd. produces the following forged shapes in Inconel 625 to customer drawing. All are open-die forged or ring-rolled from ingot or billet, not cut from plate.
Also supplied under the equivalent designations alloy 625, UNS N06625, 2.4856 and NiCr22Mo9Nb. If your drawing calls out any of these, it is the same material.
Inconel 625 chemical composition
Composition limits for UNS N06625, as applied by Jiangyin Jiangnan Metal Co., Ltd. to Inconel 625 forgings under ASTM B564. Every heat is verified by spectrographic analysis and reported on the mill certificate.
| Element | Symbol | Minimum | Maximum |
|---|---|---|---|
| Nickel | Ni | 58.0 | balance |
| Chromium | Cr | 20.0 | 23.0 |
| Molybdenum | Mo | 8.0 | 10.0 |
| Niobium + tantalum | Nb+Ta | 3.15 | 4.15 |
| Iron | Fe | – | 5.0 |
| Cobalt | Co | – | 1.0 |
| Manganese | Mn | – | 0.50 |
| Silicon | Si | – | 0.50 |
| Aluminum | Al | – | 0.40 |
| Titanium | Ti | – | 0.40 |
| Carbon | C | – | 0.10 |
| Phosphorus | P | – | 0.015 |
| Sulfur | S | – | 0.015 |
Cobalt is reported when specified by the purchaser. Tighter limits can be agreed at inquiry stage, for example restricted cobalt for nuclear service or restricted carbon.
Inconel 625 mechanical properties (ASTM B564)
ASTM B564 / ASME SB-564 defines two supply conditions for UNS N06625 forgings. State which grade you need on the inquiry, because the heat treatment, not the chemistry, is what changes.
| Condition | Section | Tensile, min | Yield 0.2 %, min | Elongation, min |
|---|---|---|---|---|
| Grade 1 (annealed) | ≤ 100 mm (4 in.) | 827 MPa (120 ksi) | 414 MPa (60 ksi) | 30 % |
| Grade 1 (annealed) | > 100 mm (4 in.) | 758 MPa (110 ksi) | 345 MPa (50 ksi) | 25 % |
| Grade 2 (solution annealed) | All sections | 690 MPa (100 ksi) | 276 MPa (40 ksi) | 30 % |
Choosing between Grade 1 and Grade 2
| Grade 1 | Grade 2 | |
|---|---|---|
| Heat treatment | Annealed, 871 °C (1600 °F) min | Solution annealed, 1093 °C (2000 °F) min |
| Grain structure | Finer grain | Coarser grain |
| Governs | Room- and mid-temperature strength | Creep and stress-rupture resistance |
| Intended service | Up to 593 °C (1100 °F) | Above 593 °C (1100 °F) |
| Typical parts | Flanges, valve bodies, shafts, subsea components | Gas-turbine parts, high-temperature vessel components |
| Optional stabilizing anneal | Not applicable | 982 °C (1800 °F) min, to raise resistance to sensitization |
Grade 1 stock can be converted to Grade 2 by an additional higher-temperature anneal, so a late change of grade is usually workable. Tell us before heat treatment is released.
Inconel 625 is not age hardenable. It is strengthened in solution, so there is no solution-plus-ageing cycle that raises its strength. If a drawing calls for an aged nickel alloy above about 1000 MPa, the intended material is normally Inconel 718 (UNS N07718) or alloy 725 (UNS N07725). We forge both, and will say so at inquiry stage rather than quote the wrong material.
Inconel 625 physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.44 g/cm³ | 0.305 lb/in³ |
| Melting range | 1290–1350 °C | 2350–2460 °F |
| Modulus of elasticity | 207.5 GPa | 30.1 × 10³ ksi |
| Thermal conductivity | 9.8 W/m·°C | 68 Btu·in/ft²·h·°F |
| Mean thermal expansion, 20–93 °C | 12.8 µm/m·°C | 7.1 × 10⁻⁶ in/in·°F |
| Specific heat | 410 J/kg·°C | 0.098 Btu/lb·°F |
| Electrical resistivity | 1.29 µΩ·m | 776 Ω·circ mil/ft |
| Magnetic permeability | ≈ 1.0006, non-magnetic. Curie temperature below −196 °C | |
| Maximum forging temperature | 1180 °C | 2156 °F |
| Oxidation resistance limit | ≈ 982 °C | ≈ 1800 °F |
| PREN (calculated) | ≈ 51 | |
PREN calculated as %Cr + 3.3 × %Mo from mid-range composition; indicative only, not a specification requirement.
Standards and equivalent designations
Inconel 625 appears under different names on drawings from different regions. Jiangyin Jiangnan Metal Co., Ltd. accepts inquiries against any of the designations below. They all refer to the same alloy.
| System | Designation |
|---|---|
| UNS | N06625 |
| Werkstoff / DIN | 2.4856 / NiCr22Mo9Nb |
| EN | NiCr22Mo9Nb |
| BS | NA 21 |
| AFNOR | NC 22 D Nb |
| JIS | NCF 625 |
| GB (China) | NS336 / GH3625 |
| Common trade names | Inconel 625, alloy 625, Nicrofer 6020 hMo, Haynes 625, Nickelvac 625 |
| Product form | Specification |
|---|---|
| Forgings and forged fittings | ASTM B564 / ASME SB-564 |
| Bar, rod and forging stock | ASTM B446 / ASME SB-446, AMS 5666 |
| Plate, sheet and strip | ASTM B443 / ASME SB-443, AMS 5599 |
| Seamless pipe and tube | ASTM B444 / ASME SB-444, AMS 5581 |
| Welded pipe and tube | ASTM B705, ASTM B704 |
| Fittings | ASTM B366 |
| Sour service | NACE MR0175 / ISO 15156 |
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 |
| Certification | EN 10204 3.1 or EN 10204 3.2 |
How we make Inconel 625 forgings
The route below is the sequence Jiangyin Jiangnan Metal Co., Ltd. follows for a typical Inconel 625 forging. Steps are added or omitted to suit the specification on your order.
- MeltingElectric arc furnace with vacuum oxygen decarburization (EAF + VOD), followed by electroslag remelting (ESR) where the specification or the section size calls for it. ESR tightens segregation and cleanliness on heavy sections.
- Open-die forgingForged from ingot or billet at a maximum of 1180 °C, reheated as often as necessary to stay in the working range, and cooled in still air. Reduction ratio and finishing temperature are controlled to develop a uniform worked structure through the section.
- Ring rollingSeamless rolled rings are produced on the ring mill for parts where a rolled circumferential grain flow beats a machined-from-solid blank on strength and material yield.
- Heat treatmentAnnealed at 871 °C minimum for Grade 1, or solution annealed at 1093 °C minimum for Grade 2, with an optional stabilizing anneal at 982 °C minimum to raise resistance to sensitization.
- MachiningRough or finish machined to drawing. Cutting speeds are kept low and tooling rigid because 625 work-hardens ahead of the cutting edge.
- Non-destructive testingUltrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, plus liquid penetrant, dimensional and visual inspection as specified.
- Certification and dispatchMill certificate to EN 10204 3.1, or EN 10204 3.2 with third-party inspection. Marking, preservation and packing to the purchase order.
Size and weight range
Inquiries outside this range are still worth sending. Capacity is quoted piece by piece.
| Form | Range |
|---|---|
| Single-piece weight | 20 kg – 10,000 kg |
| Ring outside diameter | 100 mm – 3,000 mm |
| Ring wall thickness | 20 mm – 500 mm |
| Ring height | 20 mm – 1,000 mm |
| Round bar diameter | 30 mm – 800 mm |
| Shaft length | up to 8,000 mm |
| Disc diameter | 100 mm – 2,500 mm |
| Flange outside diameter | 100 mm – 3,000 mm |
| Supply condition | Forged black, rough machined, or finish machined to drawing |
Testing, inspection and certification
Every Inconel 625 forging leaving Jiangyin Jiangnan Metal Co., Ltd. is traceable to its heat number. The following are available on order:
- Chemical analysis. Spectrographic verification of each heat against UNS N06625 limits, reported on the certificate.
- Tensile testing. Tensile strength, 0.2 % offset yield strength and elongation to ASTM B564 requirements, on test material representing the forging.
- Hardness testing. Brinell or Rockwell, including maximum-hardness limits for NACE MR0175 / ISO 15156 sour service.
- Ultrasonic testing. To EN 10228-3, SEP 1921 or ASTM A388, to the acceptance class stated on your order.
- Liquid penetrant testing. To ASTM E165 for surface indications on machined faces.
- Intergranular corrosion testing. ASTM G28 method A where specified for corrosive service.
- Impact testing. Charpy V-notch at ambient or low temperature where the code requires it.
- Grain size and metallography. To ASTM E112 where the specification calls for a controlled grain size.
- Dimensional inspection. Against your drawing, with a report issued before dispatch.
- Third-party inspection. SGS, BV, TÜV, Lloyd's or your own nominated inspector, released under EN 10204 3.2.
State the required certificate level (EN 10204 3.1 or 3.2) and any witness or hold points on the inquiry. Both affect price and lead time, and both cost less to plan in than to add on later.
Where Inconel 625 forgings are used
The combination of chloride and sour-service corrosion resistance, strength retained to high temperature and good weldability puts Inconel 625 forgings into the following applications.
| Industry | Typical forged components |
|---|---|
| Oil & gas, subsea | Wellhead and Christmas tree components, subsea connectors, deepwater production hardware, riser components, bushings, sleeves, discs |
| Valves | Valve bodies and bonnets, stems, seat rings, wedges, blocks and gate components for ball, gate, globe, check, plug valves and strainers |
| Chemical processing | Pump shafts and casings for chemical and plunger pumps, columns and towers, tanks and silos, process modules, preheaters, crystallizer equipment |
| Pressure vessels & heat exchangers | Tube sheets, forged flanges, shell and nozzle forgings, forged tubes and pipe sections, air receivers, shell-and-tube exchanger components |
| Power generation | Gas turbine and compressor discs, seamless rolled rings, spindles, gear blanks, gearbox and power-transmission components |
| Marine & shipbuilding | Propeller and pump shafts, seawater system flanges and rings, forged wheels, manifolds and rolls |
| Flue-gas & environmental | Scrubber and FGD components, stack liners, ducting flanges, expansion-joint rings |
| Aerospace | Rings, discs and bar for exhaust systems, thrust-reverser and engine hardware to AMS 5666 |
| Heavy machinery | Cement, sugar and concrete mill parts, mixers, forged crankshafts, eccentric shafts, nozzles, rolls |
| Pulp, paper & pharmaceutical | Corrosion-resistant rolls, shafts, discs and vessel components for bleaching and biochemical service |
Inconel 625 compared with C276, 825 and 718
Buyers often arrive with one of these four alloys on the drawing and a question about whether another would do the job. The table sets out the practical differences.
| Inconel 625 | Hastelloy C276 | Incoloy 825 | Inconel 718 | |
|---|---|---|---|---|
| UNS | N06625 | N10276 | N08825 | N07718 |
| Nickel | 58 % min | balance ≈ 57 % | 38–46 % | 50–55 % |
| Chromium | 20–23 % | 14.5–16.5 % | 19.5–23.5 % | 17–21 % |
| Molybdenum | 8–10 % | 15–17 % | 2.5–3.5 % | 2.8–3.3 % |
| Other key elements | Nb+Ta 3.15–4.15 % | W 3–4.5 % | Cu 1.5–3 %, Ti | Nb 4.75–5.5 %, Ti, Al |
| Strengthening | Solid solution | Solid solution | Solid solution | Age hardened (γ″) |
| PREN (calculated) | ≈ 51 | ≈ 70 | ≈ 31 | ≈ 27 |
| Typical upper service temp. | ≈ 982 °C | ≈ 677 °C long term | ≈ 538 °C | ≈ 700 °C |
| Best at | Seawater, chlorides, sour gas, high-temperature strength | Reducing acids (hydrochloric, sulfuric) | Sulfuric and phosphoric acid, cost-effective | High strength, 1275 MPa aged |
| Forging spec | ASTM B564 | ASTM B564 | ASTM B564 | ASTM B564 |
All four are forged by Jiangyin Jiangnan Metal Co., Ltd. under ASTM B564. If you are unsure which grade the service justifies, send the medium, temperature, pressure and chloride content with your inquiry and we will comment before quoting.
Frequently asked questions about Inconel 625
What is Inconel 625?
Inconel 625 (UNS N06625, W.Nr. 2.4856, NiCr22Mo9Nb) is a nickel-chromium-molybdenum-niobium superalloy with an austenitic face-centred-cubic matrix. It contains a minimum of 58 % nickel, 20.0–23.0 % chromium, 8.0–10.0 % molybdenum and 3.15–4.15 % niobium plus tantalum. Molybdenum and niobium stiffen the matrix by solid-solution strengthening, so the alloy reaches high strength without any age-hardening heat treatment. It resists pitting, crevice corrosion, chloride stress-corrosion cracking and oxidation from cryogenic temperatures up to about 982 °C.
Which standard covers Inconel 625 forgings?
ASTM B564 (ASME SB-564), Standard Specification for Nickel Alloy Forgings, is the governing specification for Inconel 625 forgings in grade UNS N06625. Related standards by product form are ASTM B446 for bar and rod, ASTM B443 for plate, sheet and strip, ASTM B444 for seamless pipe and tube, ASTM B366 for fittings, and AMS 5666 for bar, forgings and rings. Jiangyin Jiangnan Metal Co., Ltd. supplies Inconel 625 forgings to ASTM B564 and can quote against ASME SB-564 for pressure-retaining service.
What is the difference between Inconel 625 Grade 1 and Grade 2?
The difference is the annealing temperature and the resulting property set. Grade 1 is annealed at 871 °C (1600 °F) minimum, gives a finer grain and higher strength (827 MPa / 120 ksi minimum tensile, 414 MPa / 60 ksi minimum yield for sections up to 100 mm) and is intended for service up to 593 °C. Grade 2 is solution annealed at 1093 °C (2000 °F) minimum, gives a coarser grain and better creep and stress-rupture resistance, with 690 MPa (100 ksi) minimum tensile and 276 MPa (40 ksi) minimum yield, and is intended for service above 593 °C.
Can Inconel 625 be hardened by age hardening?
No. Inconel 625 is a solid-solution-strengthened alloy: its strength comes from molybdenum and niobium dissolved in the nickel-chromium matrix, not from a precipitation-hardening heat treatment. It is supplied annealed (Grade 1) or solution annealed (Grade 2). If a higher-strength age-hardenable nickel alloy is required, the usual alternatives are Inconel 718 (UNS N07718) or alloy 725 (UNS N07725).
What is the maximum service temperature of Inconel 625?
Inconel 625 resists oxidation up to approximately 982 °C (1800 °F). For load-bearing service, ASTM grade selection applies: Grade 1 annealed material is normally used up to 593 °C (1100 °F), and Grade 2 solution-annealed material is used above 593 °C where creep and stress-rupture resistance govern. The alloy is also fully usable down to cryogenic temperatures.
Is Inconel 625 magnetic?
No. Inconel 625 is non-magnetic at all normal service temperatures. Its Curie temperature is below −196 °C and its relative magnetic permeability is approximately 1.0006 at 20 °C, which is why it is specified for subsea housings, downhole tools and other applications where magnetic response is a problem.
Should I use Inconel 625 or Hastelloy C276?
Both are nickel-chromium-molybdenum alloys. Hastelloy C276 (UNS N10276) carries 15–17 % molybdenum plus 3–4.5 % tungsten and outperforms 625 in strongly reducing acids such as hydrochloric and sulfuric. Inconel 625 (UNS N06625) carries 8–10 % molybdenum plus niobium and is generally preferred where high-temperature strength, oxidation resistance to about 982 °C, seawater and chloride resistance, and weldability without post-weld heat treatment matter more. For sour service both are commonly qualified to NACE MR0175 / ISO 15156. Jiangyin Jiangnan Metal Co., Ltd. forges both grades to ASTM B564.
At what temperature is Inconel 625 forged?
Inconel 625 is open-die forged at a maximum of 1180 °C, reheated as often as necessary to stay in the working range, and cooled in still air. The alloy work-hardens rapidly, so heavy reductions and controlled finishing temperatures are used to develop a uniform grain structure before the annealing or solution-annealing heat treatment.
Do you supply EN 10204 3.1 or 3.2 certificates for Inconel 625 forgings?
Yes. Jiangyin Jiangnan Metal Co., Ltd. supplies Inconel 625 forgings with mill certification to EN 10204 3.1, or to EN 10204 3.2 with third-party inspection by SGS, BV, TÜV, Lloyd's or your own nominated inspector. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 as specified on the order.
What information do you need to quote an Inconel 625 forging?
Send a drawing or the finished dimensions, the grade and specification (for example Inconel 625 to ASTM B564 Grade 1), the required heat-treatment condition, the quantity, any non-destructive testing requirement and the certification level. Send inquiries to sales@steelforgepieces.com or call +86-189-2135-9659. Jiangyin Jiangnan Metal Co., Ltd. is located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.
Request an Inconel 625 forging quotation
Send the drawing plus the five lines below and you will get a price back without a round of clarifying questions first.
- Shape and dimensions. Drawing, sketch or finished sizes, plus the supply condition: forged black, rough machined or finish machined.
- Grade and specification. For example Inconel 625, UNS N06625, ASTM B564 Grade 1.
- Quantity. Piece count, and whether repeat orders are expected.
- Testing. Ultrasonic class, penetrant, impact, corrosion testing, hardness limits for sour service.
- Certification. EN 10204 3.1, or 3.2 with the inspection body named.
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory producing forged rings, seamless rolled rings, flanges, shafts, bars and discs in nickel alloys, stainless, tool, alloy and carbon steel.
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Phone
- +86-189-2135-9659
- sales@steelforgepieces.com
- Website
- www.steelforgepieces.com
Every price is worked out against your drawing, your specification and your certification level.