Incoloy 925 – UNS N09925
Precipitation-hardening Ni-Fe-Cr-Mo-Cu alloy for sour service
Nickel-iron-chromium alloy with molybdenum and copper, precipitation hardened with titanium and aluminum. It combines the corrosion resistance of Incoloy 825 with a minimum yield strength of 758 MPa (hot-worked bar, solution annealed and aged). It meets NACE MR0175 / ISO 15156-3 and is used in wells and wellheads with H2S: tubing hangers, valve stems, fasteners and downhole tools.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | N09925 |
| Trade names | Incoloy® 925 (Special Metals), Alloy 925 |
| Others | ASME Code Case 2218 (Section VIII Div. 1); SMC HA 46 |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM B805* / API 6ACRA* |
| Forging | API 6ACRA* / customer specification (e.g. SMC HA 46) |
| Tube | Cold-drawn tube to customer specification |
| Sour service | NACE MR0175 / ISO 15156-3 |
| Pressure vessel | ASME Code Case 2218 (Section VIII Div. 1) |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Hot-rolled bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Seamless pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Welded pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Flange and fitting | 7507.20.00 | 7507.20 | 7507.20.0000 | 7507 20 00 |
Tariff class: nickel alloy (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
UNS N09925 (Special Metals, limiting composition table)
| Element | Range (%) |
|---|---|
| Ni | 42.0 – 46.0 |
| Cr | 19.5 – 22.5 |
| Fe | ≥ 22.0 |
| Mo | 2.5 – 3.5 |
| Cu | 1.5 – 3.0 |
| Ti | 1.9 – 2.4 |
| Al | 0.1 – 0.5 |
| Nb | ≤ 0.5 |
| Mn | ≤ 1.0 |
| Si | ≤ 0.5 |
| C | ≤ 0.03 |
| S | ≤ 0.03 |
Mechanical properties
Solution annealed and aged – minimums of Special Metals specification HA 46 for hot-worked bar Ø 25 – 254 mm (cold-drawn bar Ø 15.9 – 76.2 mm in parentheses) and typical manufacturer values
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 758 MPa (cold drawn: ≥ 724 MPa) |
| Tensile strength | ≥ 965 MPa |
| Elongation | ≥ 18% |
| Reduction of area | ≥ 25% |
| Hardness | 26 – 38 HRC |
| Charpy V (−60 °C) | ≥ 47 J (average) |
| Typical solution annealed, not aged | Rp0.2 271 MPa; Rm 685 MPa; A 56%; 76 HRB |
| Typical solution annealed and aged | Rp0.2 832 MPa; Rm 1,154 MPa; A 27%; 32 HRC |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.08 g/cm³ |
| Melting range | 1,311 – 1,366 °C |
| Modulus of elasticity (21 °C) | 199 GPa |
| Thermal conductivity (23 °C) | 12.0 W/m·K |
| Thermal expansion (25–100 °C) | 13.2 µm/m·K |
| Electrical resistivity | 1.17 µΩ·m |
| Magnetic permeability | 1.001 (non-magnetic) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Retains a large part of its strength up to ≈ 650 °C (Special Metals). In sour service, the ISO 15156-3 (Annex A) limits for temperature, H2S partial pressure, chlorides and sulfur apply, with controlled hardness (max. 38 HRC*). |
| Heat treatment | Solution annealing at 980 – 1,040 °C for 30 min to 4 h; air cool up to Ø 25 mm and water quench above that. Aging: 732 – 749 °C for 6 – 9 h, furnace cool to 621 °C and hold at 621 ± 8 °C for a total aging time of 18 h; then air cool or faster. For direct aging, final hot working should be done between 870 and 980 °C. |
| Welding | GTAW (TIG) and GMAW (pulsed or spray) with Inconel 725 filler metal (INCO-WELD 725NDUR), which ages with the joint and gives higher strength than 925-composition wire. Submerged arc and covered electrodes are not recommended. Welding in the annealed condition followed by anneal plus age gives the toughest joint (Charpy ≈ 51 – 57 J in manufacturer tests). |
| Machining | It work hardens quickly, like other age-hardenable nickel alloys. Rough machine in the annealed condition (≈ 80 HRB) and finish after aging (≈ 40 HRC). Carbide gives the highest speeds; sharp tools, constant feed and abundant coolant. |
Typical applications
- Tubing hangers and wellhead components (API 6A)
- Valve stems, seats and trim for sour service
- High-strength fasteners and studs
- Downhole tools: packers, landing nipples and tool joints
- Tubulars and well components with H2S, CO2 and chlorides
- Pump shafts and marine shafting
- High-strength piping
Alternatives: Inconel 718 when mechanical strength is the main criterion; Inconel 725 (UNS N07725) for more severe sour service and higher pitting resistance; Incoloy 825 when annealed strength is enough; Monel K-500 in seawater without H2S.
Incoloy 925: complete guide
What Incoloy 925 is
Incoloy 925 is the precipitation-hardening version of Incoloy 825: the same nickel-iron-chromium base with molybdenum and copper, plus titanium (1.9 – 2.4%) and aluminum, which form the gamma-prime precipitate Ni3(Ti,Al) on aging. Yield strength of aged material exceeds 750 MPa, with corrosion resistance close to that of 825. It belongs to the nickel alloys.
Sour service (H2S) in oil and gas
Nickel (42 – 46%) protects against chloride stress corrosion cracking; molybdenum and copper give resistance to reducing media and pitting. The alloy resists sulfide stress cracking and stress corrosion in oil and gas with H2S, so it is listed in NACE MR0175 / ISO 15156-3 and used in API 6A equipment. For sour service, the purchase order should require the solution annealed and aged condition, the hardness range and Charpy testing at −60 °C.
When to choose 925, 718 or 725
Inconel 718 has higher strength and is the standard for high-pressure components. Inconel 725 combines strength close to 718 with corrosion resistance close to 625. 925 sits in between: stronger than Monel K-500 and with corrosion resistance close to 825, in large-diameter bars for hangers and machined bodies.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, heat treatment in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of Incoloy 925?
Per UNS N09925 (Special Metals, limiting composition table): Ni 42.0 – 46.0; Cr 19.5 – 22.5; Fe ≥ 22.0; Mo 2.5 – 3.5; Cu 1.5 – 3.0; Ti 1.9 – 2.4.
Which standards cover Incoloy 925?
Bar: ASTM B805* / API 6ACRA*. Forging: API 6ACRA* / customer specification (e.g. SMC HA 46). Tube: Cold-drawn tube to customer specification. Sour service: NACE MR0175 / ISO 15156-3. Pressure vessel: ASME Code Case 2218 (Section VIII Div. 1).
Up to what temperature can Incoloy 925 be used?
Retains a large part of its strength up to ≈ 650 °C (Special Metals). In sour service, the ISO 15156-3 (Annex A) limits for temperature, H2S partial pressure, chlorides and sulfur apply, with controlled hardness (max. 38 HRC*).
Which materials can replace Incoloy 925?
Inconel 718 when mechanical strength is the main criterion; Inconel 725 (UNS N07725) for more severe sour service and higher pitting resistance; Incoloy 825 when annealed strength is enough; Monel K-500 in seawater without H2S.
What is the difference between Incoloy 925 and Incoloy 825?
The base is the same (Ni-Fe-Cr-Mo-Cu), but 925 has 1.9 – 2.4% titanium and some aluminum, which allow age hardening. Solution annealed and aged, 925 has a minimum yield strength of 758 MPa; 825 is used annealed and is much weaker. Corrosion resistance is similar.
Does Incoloy 925 meet NACE MR0175?
Yes. The solution annealed and aged alloy is listed in NACE MR0175 / ISO 15156-3, within the environmental limits of the standard and with controlled hardness (max. 38 HRC*). The manufacturer states that the values of its specification meet NACE MR0175.
How is Incoloy 925 aged?
Solution anneal at 980 – 1,040 °C, then age at 732 – 749 °C for 6 – 9 h, furnace cool to 621 °C and hold there for a total of 18 h, with final air cooling.
