Alloy 925
Also known as Incoloy® 925, UNS N09925
Alloy 925 is an age-hardened nickel-iron-chromium alloy combining very high strength with corrosion resistance in sour service.
Alloy 925 (UNS N09925) is a precipitation-hardenable Nickel-Iron-Chromium alloy with additions of Molybdenum, Copper, Titanium and Aluminium. Solution annealed and aged to provide proof stress in the range 758-965 N/mm², it is particularly suited to sour downhole environments containing chlorides, CO₂ and H₂S.
Approved under NACE MR0175-3 / ISO 15156-3, ASTM B805 and API 6A CRA. Its corrosion performance in sour crude oil and natural gas wells is exceptional; its very high strength is also applicable to tooling and highly loaded structural components. Each complete batch is ultrasonically tested.
We stock bar in the UK and USA. Plate, tube and fittings are available on enquiry; forgings and castings to order.
- Corrosion performance particularly suited to sour downhole crude oil and gas wells
- Very high strength applicable to tooling and critical component load reduction
- Excellent resistance to stress corrosion cracking
- NACE MR0175-3 / ISO 15156-3 approved
| Element | Min | Max |
|---|---|---|
| Nickel (Ni) | 42.0 | 46.0 |
| Iron (Fe) | Bal | |
| Chromium (Cr) | 19.50 | 22.50 |
| Molybdenum (Mo) | 2.50 | 3.50 |
| Copper (Cu) | 1.50 | 3.00 |
| Titanium (Ti) | 1.90 | 2.40 |
| Niobium+Tantalum (Nb+Ta) | 0.08 | 0.50 |
| Aluminium (Al) | 0.10 | 0.50 |
| Manganese (Mn) | - | 1.00 |
| Silicon (Si) | - | 0.35 |
| Carbon (C) | - | 0.025 |
| Phosphorus (P) | - | 0.020 |
| Sulphur (S) | - | 0.003 |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 110 ksi | 758 N/mm² |
| 0.2% Proof stress | 110-140 ksi | 758-965 N/mm² |
| Tensile strength (min) | 140 ksi | 965 N/mm² |
| Elongation (5.65√S0 & 4D) | 18% | |
| Reduction of area | 25% | |
| Hardness | 38 HRC max | |
| Impact strength (-60°C) long. | 35 ft.lb av (32 ft.lb min) | 47 J av (43 J min) |
| Property | Value |
|---|---|
| Density (kg/m³) | 8080 |
| Magnetic permeability (20°C) | 1.001 |
| Young's modulus (kN/mm²) | 199 |
| Specific heat, 20°C (J/kg.K) | 435 |
| Specific electrical resistance, 20°C (µΩ.m) | 1.17 |
| Electrical conductivity, 20°C (mΩ/mm²) | 0.25 (1.48% IACS) |
| Thermal conductivity, 20°C (W/m.K) | 12.0 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/K) | 13.2 x 10⁻⁶ |
Equivalents & cross-references
Standard designations
- UNS
- N09925Unified Numbering System
- ASTM
- B805Rod and bar
- API
- 6ACRACorrosion-resistant alloy
- NACE
- MR0175 / ISO 15156-3Sour service
Alloy 925 is also designated UNS N09925, ASTM B805, API 6ACRA and NACE MR0175 / ISO 15156-3.
Trade name equivalents
-
Incoloy 925
Special Metals Corporation
Incoloy 925 is a trade name of Special Metals Corporation for Alloy 925.
Common questions
What is the UNS number for Alloy 925?
Alloy 925 is a precipitation-hardenable nickel-iron-chromium alloy with molybdenum, copper, titanium and aluminium additions, covered by UNS N09925, ASTM B805 and API 6A CRA, and listed in NACE MR0175-3/ISO 15156-3. It is supplied in the solution annealed and aged condition, strengthened by Ni3(Al,Ti) gamma-prime precipitates in a similar way to Alloys K-500, 718 and 725. Langley Alloys stocks it as bar; plate, tube and fittings are available on enquiry, and forgings and castings are to order.
What is Alloy 925 used for?
Alloy 925 is used for downhole equipment for corrosive and sour service such as valves, hangers, tool joints and packers; marine and pump shafts; high strength fasteners; and chemical process industry components. It is particularly suited to down-hole applications in sour gas wells but can also be used in less aggressive applications.
Is Alloy 925 suitable for sour gas wells?
Yes. Alloy 925's balanced composition makes it particularly suited to the sour environments of down-hole crude oil and natural gas wells. High nickel gives protection against stress corrosion cracking, while molybdenum and copper resist reducing environments and chromium resists oxidising environments; molybdenum also raises the Pitting Resistance Equivalent Number (PREN) above 26. It resists general, pitting, crevice and stress corrosion cracking in most aqueous environments where chloride or sulphide ions are present, and provides very high strength (0.2% proof stress of 758-965 N/mm²).
What is the density of Alloy 925?
Alloy 925 has a density of approximately 8.08 g/cm³ (8080 kg/m³).
Is Alloy 925 magnetic?
Effectively no. Alloy 925 has a very low magnetic permeability (around 1.001) and is treated as non-magnetic for most purposes.
Datasheets
718-class strength at lower cost
In this Technical Corner, Rodney unpacks Alloy 925: essentially Alloy 825 boosted through precipitation hardening to a strength comparable with Inconel 718, but at a lower cost.
That makes it a compelling drop-in alternative to 718 for oil and gas downhole tooling, and it is now available in heavy-wall tube form as well as bar.
Visit our YouTube channelAlloy 925 is supplied solution annealed and aged; each complete batch is ultrasonically tested and all bars visually inspected, with additional macro-etching and microstructure certification routinely undertaken.
Tools for this grade
Sour-service screen (NACE MR0175)
Sour-Service Screen
Work out whether a service is sour from the H2S partial pressure, and see each alloy's NACE MR0175 / ISO 15156 status and hardness limit. A first-pass screen for oil & gas material selection - the full environmental envelope for a grade is set in ISO 15156-3 Annex A.
Candidate grade
| Grade | Family | NACE status | Hardness limit |
|---|
First-pass screen only. This shows whether the service is sour (from H2S partial pressure) and each material group's NACE MR0175 hardness limit and general suitability. It does not reproduce the full environmental windows (maximum H2S partial pressure, temperature, chloride, in-situ pH per grade) - those are in ISO 15156-3 Annex A and must be checked there for the specific grade, product form and condition. Qualification also depends on heat treatment, cold work and welding.
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