Definition
What is Incoloy 925?
Incoloy 925 is an age-hardenable nickel-iron-chromium alloy, designated UNS N09925, developed to combine the corrosion resistance of Alloy 825 with roughly twice its strength. The strength comes from precipitation of gamma prime, Ni3(Al,Ti), during ageing. This is the same mechanism used in Alloy K-500, Alloy 718 and Alloy 725, and because it does not rely on cold work, heavy forgings can be strengthened uniformly through section.
What each addition does:
- Nickel, 42 to 46%. Enough austenite stability to resist chloride-ion stress-corrosion cracking, the failure mode that rules out austenitic stainless steels in hot brines.
- Chromium, 19.5 to 22.5%. Passivity in oxidising media such as nitric acid, nitrates and oxidising salts.
- Molybdenum, 2.5 to 3.5%. Resistance to pitting and crevice attack. It lifts the pitting resistance equivalent number (PREN) above 26.
- Copper, 1.5 to 3.0%. With the nickel, resistance to reducing acids, in particular sulphuric and phosphoric acid.
- Titanium 1.9 to 2.4% with aluminium 0.10 to 0.50%. The gamma prime formers. They allow the alloy to be aged, and they are also why it needs a controlled thermal history through forging and heat treatment.
Naming, and one common error. Alloy 925 is sold as Incoloy 925, as Alloy 925, and incorrectly as "Inconel 925". INCOLOY and INCONEL are separate registered trademarks of the Special Metals Corporation group, and 925 belongs to the INCOLOY family. The alloy is also frequently listed with Werkstoff number 2.4858, but 2.4858 is Alloy 825, not 925. Alloy 925 has no widely recognised EN material number, so purchase orders should be written against UNS N09925 plus the applicable ASTM or API specification. Jiangyin Jiangnan Metal quotes and certifies against UNS N09925 for that reason.
Chemistry
Chemical composition of Incoloy 925 (UNS N09925)
Composition limits in weight percent, as given for UNS N09925 in ASTM B637 and ASTM B805.
| Element | Minimum % | Maximum % | Function in the alloy |
|---|---|---|---|
| Nickel (Ni) | 42.0 | 46.0 | Austenite stability, chloride SCC resistance |
| Iron (Fe) | 22.0 | balance | Base, cost control |
| Chromium (Cr) | 19.5 | 22.5 | Passivity in oxidising media |
| Molybdenum (Mo) | 2.5 | 3.5 | Pitting and crevice resistance |
| Copper (Cu) | 1.5 | 3.0 | Reducing acid resistance |
| Titanium (Ti) | 1.9 | 2.4 | Gamma prime former, age hardening |
| Aluminium (Al) | 0.10 | 0.50 | Gamma prime former, age hardening |
| Niobium (Nb) | none | 0.50 | Residual limit |
| Manganese (Mn) | none | 1.00 | Deoxidiser, residual |
| Silicon (Si) | none | 0.50 | Deoxidiser, residual |
| Carbon (C) | none | 0.03 | Held low to limit carbides |
| Sulphur (S) | none | 0.03 | Residual, kept low for hot workability |
| Melting practice at Jiangyin Jiangnan Metal: EAF + VOD, followed by electro-slag remelting (ESR) where the specification or the project calls for a remelted ingot. ESR is normally requested for subsea and critical wellhead work to tighten segregation and inclusion content. | |||
Strength
Mechanical properties of Alloy 925 forgings
Two conditions matter commercially: solution annealed, in which the alloy is soft and formable, and solution annealed plus aged, which is what a strength critical order specifies.
| Property | Metric | Imperial | Basis |
|---|---|---|---|
| Tensile strength | 965 MPa min | 140,000 psi min | ASTM B637 |
| Yield strength (0.2% offset) | 758 MPa min | 110,000 psi min | ASTM B637 |
| Elongation (4D) | 18% min | 18% min | ASTM B637 |
| Reduction of area | 25% min | 25% min | ASTM B637 |
| Hardness | 38 HRC max | 38 HRC max | ASTM B637 |
| Charpy V-notch, low temperature | typically 47 J avg / 38 J single at -60 °C | 35 / 28 ft·lb | Project or API specification, not ASTM B637 |
| Impact energy is not an ASTM B637 requirement. State it on the enquiry if your project needs it, together with the test temperature. Subsea packages usually call for -46 °C or -60 °C. | |||
| Property | Typical range |
|---|---|
| Tensile strength | 586 to 724 MPa (85 to 105 ksi) |
| Yield strength (0.2%) | approx. 310 to 450 MPa (45 to 65 ksi) |
| Elongation | 30% and above |
| Hardness | approx. 20 to 30 HRC |
Where the test specimen is taken changes the result
Specimen location should be written into the purchase order. For large disc forgings over 3,226 mm² (50 in.²) in cross-section, and for rings 76 mm (3 in.) and thicker, ASTM B637 permits tension specimens to be machined tangentially from near the centre of the disc, or radially from the ring. Those orientations sample the weakest direction relative to grain flow, so agreeing the location and orientation up front avoids an argument at witness testing.
Ageing and hardness are linked. ASTM B637 caps hardness at 38 HRC while requiring 758 MPa minimum yield, so the ageing cycle has to be controlled tightly. Under-age and the yield strength fails; over-age and the hardness reading, or the sour service hardness limit, fails. Jiangyin Jiangnan Metal ages Alloy 925 in instrumented furnaces with recorded charts, and reports hardness on the same test block as the tensile result.
Physical constants
Physical properties of Incoloy 925
Room temperature values except the melting range. Use these for weight calculation, thermal stress work and machining feeds.
| Property | Value (metric) | Value (imperial) |
|---|---|---|
| Density | 8.08 g/cm³ | 0.292 lb/in³ |
| Melting range | 1311 to 1366 °C | 2392 to 2490 °F |
| Modulus of elasticity, 20 °C | 199 GPa | 28.9 x 10³ ksi |
| Shear modulus, 20 °C | 77 GPa | 11.2 x 10³ ksi |
| Mean coefficient of expansion | 15.7 µm/m·°C (20 to 700 °C) | 9.0 µin/in·°F (70 to 1200 °F) |
| Thermal conductivity, 23 °C | 12.0 W/m·°C | 83.1 Btu·in/ft²·h·°F |
| Electrical resistivity | 1.17 µΩ·m | 701 Ω·cmil/ft |
| Relative permeability at 15.9 kA/m | 1.001 max | 1.001 max (200 oersteds) |
| PREN | above 26 | above 26 |
| Usual maximum service temperature | approx. 538 °C | approx. 1000 °F |
| Quick weight check: mass in kg is approximately the volume in cm³ multiplied by 0.00808. A 600 mm OD x 300 mm ID x 150 mm high ring encloses 31,800 cm³ and weighs about 257 kg in Alloy 925. | ||
Route
How Incoloy 925 forgings are made and heat treated
Alloy 925 work-hardens quickly and its properties depend on thermal history, so each step below constrains the next.
- Melting: EAF and VOD, plus ESR when specified Electric arc melting with vacuum oxygen decarburisation controls carbon, sulphur and gas content. Electro-slag remelting is added for critical wellhead and subsea material to improve soundness and reduce segregation.
- Ingot conditioning and upsetting The ingot is heated and upset to break down the as-cast structure. This is where the forging reduction ratio is established, and a ring cut from bar cannot replicate it.
- Open-die forging or ring rolling, roughly 900 to 1180 °C Hot working is carried out in this range, with finishing passes at the low end to refine grain size. Alloy 925 loses ductility quickly below the range, so reheats are planned rather than improvised.
- Solution annealing Typically about 980 to 1040 °C followed by rapid cooling, which dissolves the gamma prime so the later ageing response is uniform. Material ordered annealed for subsequent forming or welding stops here.
- Ageing (precipitation hardening) A double cycle is normal: hold near 730 to 750 °C for 6 to 9 hours, furnace cool to about 620 °C and hold to complete roughly 18 hours in total, then air cool. This is the step that takes the alloy to 758 MPa minimum yield inside the 38 HRC ceiling.
- Rough or finish machining Machining behaviour resembles the harder stainless grades but with much higher strength and rapid work hardening. Rigid setups, positive feed, no dwelling, and coolant throughout.
- Non-destructive examination Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 as specified, plus liquid penetrant examination on machined surfaces where the project requires it.
- Certification and release Chemistry, mechanical results, hardness, heat treatment charts and NDE reports issued as an EN 10204 3.1 certificate, or 3.2 with third-party endorsement by SGS, BV, TUV or Lloyd's when the order calls for it.
Two decisions set the route. The supply condition, annealed or annealed and aged, and whether the ingot must be ESR remelted. Tell us those on the enquiry and the rest follows from your specification.
Environment
Corrosion resistance and sour service qualification
Alloy 925 was designed for sour oil and gas production and that is still where most of it is used. Its corrosion behaviour is broadly that of Alloy 825, since the two share almost the same Ni-Cr-Mo-Cu backbone, with the localised corrosion advantage that comes from a PREN above 26 and roughly double the strength.
- Sulphide stress cracking (SSC) in H2S. Resistant at strength levels where carbon and low alloy steels, capped at 22 HRC, would crack.
- Chloride stress corrosion cracking. The 42 to 46% nickel content puts the alloy above the range where austenitic stainless steels fail in hot chloride service.
- Pitting and crevice corrosion. Molybdenum assisted resistance in produced water, completion brines and seawater.
- Reducing acids. Nickel with copper gives useful resistance to sulphuric and phosphoric acid, and the chromium covers oxidising media such as nitric acid and nitrates.
- CO2 corrosion. Resistant in the high CO2, high chloride conditions common in deep gas wells.
Sour service acceptance is conditional. Alloy 925 is listed in NACE MR0175 / ISO 15156-3 as a precipitation hardenable nickel alloy accepted for sour service, but the applicable Annex A table sets limits on H2S partial pressure, chloride concentration, in-situ pH, temperature and hardness for the qualified condition. A blanket "NACE compliant" statement on a mill certificate means very little on its own.
State your service envelope on the enquiry, that is H2S partial pressure, chloride, pH and maximum temperature, and Jiangyin Jiangnan Metal will confirm in writing which Annex A entry the material is supplied against, together with the hardness limit applied at test.
Capability
Incoloy 925 forgings we produce
All items are forged to customer drawing or to a standard dimensional specification, in the rough, rough machined or finish machined state.
| Forged form | Typical end use | Dimensional basis |
|---|---|---|
| Seamless rolled rings | Casing hangers, seal rings, bearing races, tension rings | To drawing |
| Flanges | Wellhead and process connections | ASME B16.5 / B16.47, or to drawing |
| Round bars and forging stock | Stems, studs, fasteners, machining stock | Diameter x length |
| Shafts and spindles | Chemical and plunger pumps, mixers, marine shafting | To drawing |
| Discs, disks and blanks | Closures, blind flanges, valve discs | To drawing |
| Sleeves and bushings | Downhole tools, wear components | To drawing |
| Tube sheets | Shell and tube heat exchangers | To drawing, with drilling if required |
| Valve bodies, seats and stems | Ball, gate, globe, check and plug valves | To drawing |
| Hollow bars, tubes and pipe forgings | Pressure parts, nipples, couplings | OD x ID x length |
| Nozzles, blocks and crankshafts | Process modules, mills, compressors | To drawing |
| Sizes are forged to drawing. Send the finished dimensions and the machining allowance you expect, and we will confirm the forged size, the piece weight and the delivery date. | ||
Where it is used
Applications for Alloy 925 forgings
| Industry | Forged components | Why Alloy 925 |
|---|---|---|
| Oil and gas, downhole | Hangers, landing nipples, packers, tool joints, tubing components | High strength with SSC resistance in sour wells |
| Subsea and wellhead | Valve bodies and stems, connectors, seal rings, christmas tree parts | Chloride SCC resistance with low temperature toughness |
| Chemical process | Pump shafts, plunger pumps, sleeves, impeller hubs | Reducing acid resistance with fatigue strength |
| Pressure equipment | Flanges, tube sheets, shells, nozzles, heat exchanger parts | Corrosion resistance in aggressive process streams |
| Marine and offshore | Shafting, fasteners, deck and riser hardware | Seawater pitting and crevice resistance |
| Power and rotating equipment | Rings, spindles, gears, compressor and turbine hardware | Strength retention to about 538 °C |
Selection
Incoloy 925 compared with 825, 718, 725 and 945
The four alloys 925 is most often weighed against, and the reason a project moves from one to another.
| Alloy | UNS | Nominal Ni % | Typical min. yield | Strengthening | Choose it when |
|---|---|---|---|---|---|
| Incoloy 925 | N09925 | 42 to 46 | 758 MPa (110 ksi) | Gamma prime Ni3(Al,Ti), aged | You need 825 type corrosion resistance at roughly double the strength, in sour service |
| Incoloy 825 | N08825 | 38 to 46 | 241 MPa (35 ksi) | Solid solution, not ageable | Corrosion governs and strength does not. Easier to weld and form |
| Inconel 718 | N07718 | 50 to 55 | 1034 MPa (150 ksi) | Gamma double prime Ni3Nb, aged | You need more strength and high temperature capability, and brine corrosion is less severe |
| Inconel 725 | N07725 | 55 to 59 | 827 MPa (120 ksi) | Gamma double prime Ni3Nb, aged | Sour service is more severe than 925 is qualified for and budget allows a higher nickel alloy |
| Incoloy 945 / 945X | N09945 | 45 to 55 | 758 to 931 MPa (110 to 135 ksi) | Gamma prime and double prime, aged | You want 925 class corrosion resistance with a higher strength grade available |
| How selection usually runs on our enquiries: start from 825 for corrosion alone, move to 925 when the part must carry load, move to 725 or 945 when the sour service envelope or the strength requirement exceeds what 925 is qualified for, and move to 718 when temperature and strength dominate and chloride SCC does not. | |||||
Specifications
Standards and designations for UNS N09925
| Reference | Scope, and how it applies to forgings |
|---|---|
| ASTM B637 | Precipitation hardening and cold worked nickel alloy bars, forgings and forging stock. The primary specification for Alloy 925 forgings, and the source of the composition and mechanical requirements in Tables 1 and 2. |
| ASTM B805 | Precipitation hardening nickel alloys, bar and wire, covering UNS N09925 among others. Applies to bar, forging stock and fastener stock. |
| ASTM B983 | Precipitation hardened or cold worked seamless nickel alloy pipe and tube. |
| ASME BPVC Code Case 2218 | Permits use of Alloy 925 under Section VIII Division 1 pressure vessel construction. |
| API 6ACRA | Age hardenable nickel based alloys for oil and gas drilling and production equipment. The usual route for wellhead forgings. |
| NACE MR0175 / ISO 15156-3 | Corrosion resistant alloys for H2S containing production environments. Sets the environmental and hardness limits for the qualified condition. |
| ISO 13680 | CRA seamless tubes for casing, tubing and coupling stock, where 925 is used in tubular form. |
| EN 10204 | Inspection document type. 3.1 is issued by our works, 3.2 is counter-endorsed by a third party. |
| EN 10228-3, SEP 1921, ASTM A388 | Ultrasonic examination procedures and acceptance classes applied to our forgings. |
| Designations | UNS N09925, Alloy 925, Incoloy 925. Sometimes written "Inconel 925", which is incorrect. No recognised EN Werkstoff number. |
Ordering
Request a quotation for Incoloy 925 forgings
Send a drawing, or the six items below, and we can quote without a second round of questions.
What to include in the enquiry
- Grade and specification UNS N09925 to ASTM B637, ASTM B805, API 6ACRA or your project specification.
- Form, quantity and dimensions Drawing preferred. Otherwise OD x ID x height for rings, or diameter x length for bars, and the machining allowance you expect.
- Supply condition Solution annealed, or solution annealed and aged, and whether ESR remelted ingot is required.
- Test and NDE requirements Tensile, hardness, impact energy and test temperature, UT class and acceptance standard, PT if needed, specimen location for heavy sections.
- Sour service envelope, if applicable H2S partial pressure, chloride content, in-situ pH and maximum temperature, so the NACE MR0175 / ISO 15156-3 basis can be confirmed.
- Certification and delivery EN 10204 3.1 or 3.2, third-party inspection if required, destination port and required delivery date.
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory producing nickel alloy, stainless, alloy, carbon and tool steel forgings for export: rings, flanges, bars, shafts, discs and seamless rolled rings.
- AddressNo.1 Chengxiqiao Road, Zhouzhuang Town,
Jiangyin City, Jiangsu Province, China - Telephone and WhatsApp+86 189 2135 9659
- Emailsales@steelforgepieces.com
- Websitewww.steelforgepieces.com
- Material certificateEN 10204 3.1, or 3.2 with third-party endorsement
Data reference. Jiangyin Jiangnan Metal Co., Ltd. (2026) Incoloy 925 forgings (UNS N09925): composition, mechanical and physical properties, and forging route. Jiangyin, Jiangsu, China. Published at http://www.steelforgepieces.com/Nickel-Alloy/Incoloy-925.html. Composition and mechanical limits reproduced from ASTM B637 and ASTM B805. Reproduction is permitted with attribution to Jiangyin Jiangnan Metal Co., Ltd.
Questions
Frequently asked questions about Incoloy 925
What is Incoloy 925?
Incoloy 925, designated UNS N09925, is an age-hardenable nickel-iron-chromium alloy containing 42 to 46% nickel, 19.5 to 22.5% chromium, 2.5 to 3.5% molybdenum, 1.5 to 3.0% copper, 1.9 to 2.4% titanium and 0.10 to 0.50% aluminium. Titanium and aluminium form gamma prime precipitates during ageing, which gives high strength alongside the corrosion resistance of Alloy 825.
Is Incoloy 925 the same as Inconel 925?
There is no INCONEL 925. INCOLOY and INCONEL are separate registered trademarks of the Special Metals Corporation group, and alloy 925 belongs to the INCOLOY family. "Inconel 925" is a common misnomer for the same material. Order against UNS N09925 to avoid ambiguity.
What are the mechanical properties of Incoloy 925 forgings?
In the solution annealed and aged condition, ASTM B637 requires a minimum tensile strength of 965 MPa (140 ksi), minimum 0.2% yield strength of 758 MPa (110 ksi), minimum elongation of 18% in 4D, minimum reduction of area of 25%, and a maximum hardness of 38 HRC.
Is Incoloy 925 acceptable for sour service under NACE MR0175?
Yes. Alloy 925 is listed in NACE MR0175 / ISO 15156-3 as a precipitation hardenable nickel alloy for H2S service, but acceptance is conditional on the H2S partial pressure, chloride content, in-situ pH, temperature and hardness limits given in the applicable Annex A table. The service envelope has to be stated so the correct entry can be confirmed.
What is the difference between Incoloy 925 and Incoloy 825?
They share a similar nickel, chromium, molybdenum and copper composition and comparable corrosion resistance, but 825 is solid solution and cannot be age hardened, with about 241 MPa (35 ksi) minimum yield strength. Alloy 925 adds titanium and aluminium so it can be aged to 758 MPa (110 ksi) minimum yield, roughly three times the yield strength.
What standards cover Incoloy 925 forgings?
ASTM B637 covers bars, forgings and forging stock, ASTM B805 covers bar and wire, and ASTM B983 covers seamless pipe and tube. API 6ACRA applies to age hardenable nickel alloys for drilling and production equipment, NACE MR0175 / ISO 15156-3 governs sour service, and ASME Code Case 2218 permits Section VIII Division 1 use.
Can Incoloy 925 be welded?
Yes. GTAW, GMAW, SMAW and submerged arc welding are all used, with matching or nickel alloy filler selected for the service. The weld region loses the aged condition, so components that need uniform strength are normally re-solution treated and re-aged after welding, or welded in the annealed condition and aged afterwards.
What is the maximum service temperature of Alloy 925?
Alloy 925 is normally used up to about 538 °C (1000 °F). Above that the gamma prime strengthening coarsens and strength falls away, so higher temperature duty is usually moved to Alloy 718 or another gamma double prime strengthened grade.
Is Incoloy 925 magnetic, and what is its density?
It is effectively non-magnetic, with relative permeability of 1.001 maximum at 15.9 kA/m (200 oersteds). Density is 8.08 g/cm³ (0.292 lb/in³), so forging weight in kilograms is approximately the volume in cubic centimetres multiplied by 0.00808.
Who supplies Incoloy 925 open-die forgings from China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forging UNS N09925 rings, flanges, bars, shafts, discs, sleeves and tube sheets to ASTM B637 with EN 10204 3.1 or 3.2 certification. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
What is the price and lead time for Alloy 925 forgings?
Price depends on the nickel and molybdenum content of the alloy at the time of order, the forged weight including machining allowance, the supply condition, and the testing package. Send the drawing, quantity, specification and required certification to sales@steelforgepieces.com for a firm price and delivery date.