Incoloy 925 (UNS N09925) is the workhorse age-hardenable nickel-iron-chromium alloy for downhole oil and gas service. The combination of 110 ksi minimum yield strength (aged condition), NACE MR0175 qualification to 1000 psi H₂S partial pressure, chloride resistance to saturation, and qualified envelope to 400°F covers the operating window of every common production tubing, packer, landing nipple, completion safety valve, tool joint, hanger and downhole bolting application. The alloy is used in vertical, horizontal, deviated and HPHT wells; it is the default specification when sour content disqualifies duplex 2205 and high strength disqualifies Incoloy 825. TorqBolt manufactures Incoloy 925 downhole bolting (stud bolts, heavy hex nuts, hex bolts), bar/forging stock and finished components per ASTM B805, API 6A, NACE MR0175 and ISO 15156-3 with EN 10204 3.1/3.2 MTC.
Need Incoloy 925 downhole components? Email info@torqbolt.com with the well profile (depth, BHT, BHP, H₂S concentration, CO₂ concentration, chloride concentration, design stress) and component requirement. WhatsApp +91-22-66157017.
Downhole Components Manufactured in Incoloy 925
| Component | Standard | Why Incoloy 925 |
|---|---|---|
| Production tubing | ASTM B983 / API 5CRA | 110 ksi YS for high-pressure wells; sour-service qualified |
| Packer bodies + mandrels | API 11D1 / customer spec | Sour-service qualification + age-hardened strength |
| Landing nipples + seating nipples | API 14L / customer spec | Wear resistance + corrosion in chloride-rich completion fluid |
| Completion safety valve (SSSV) bodies | API 14A | Reliability under sour H₂S + cyclic loading |
| Tubing & casing hangers | API 6A wellhead hangers | High-strength sour-service CRA |
| Tool joints / drill string subs | API Spec 7-1 / customer | Fatigue + sour H₂S in extended-reach drilling |
| Perforating gun bodies | API 19B | Strength + non-magnetic for orientation |
| Downhole bolting, stud bolts, hex nuts | API 6A / ASTM B805 | 110 ksi YS + 35 HRC NACE cap |
| Bottom-hole flow control valves | API 14A / customer spec | Erosion + sour gas resistance |
| MWD/LWD downhole tool housings | customer spec | Low magnetic permeability (μr ~1.005) for instrument signal integrity |
Sour-Service Envelope
| Parameter | Qualified Range (NACE MR0175 Table A.10) |
|---|---|
| H₂S Partial Pressure | Up to 1000 psi (6.9 MPa), effectively unrestricted for most wells |
| Maximum Service Temperature | 400°F (204°C) |
| Chloride Concentration | Up to saturation |
| CO₂ Partial Pressure | Tested to 100 psi in NACE TM0177 C-ring solution |
| Hardness Cap (CW + Aged) | 35 HRC (Rockwell C scale) |
| Sulfur (free) Tolerance | Per Special Metals Table 10, resistance verified in elemental sulfur environments |
For wells exceeding the qualified envelope (deep gas with bottom-hole H₂S > 1000 psi, BHT > 400°F, or both), the alternatives are: (a) cold-worked + aged Incoloy 925 with project-specific qualification per Special Metals C-ring Tables 8–9 (no SSC seen up to 46 HRC in NACE solution at 350°F); (b) Inconel 725 / 945X (UNS N09945, the next-generation oilfield CRA); (c) Inconel 718 only at H₂S < 15 psi.
Why Not Cheaper Alternatives?
- Duplex 2205 (UNS S32205): Disqualified above 1.5 psi H₂S at 65°C per NACE Table A.21. For most sour wells, 2205 is not qualified at all.
- Incoloy 825 (UNS N08825): Solid-solution only at ~45 ksi YS, insufficient for API 6A wellhead bolting strength requirements (typically ≥75 ksi YS). Qualified for sour service only up to 15 psi H₂S.
- Carbon steel (4140, 4145): Disqualified entirely, SSC failure within hours in any wet H₂S environment.
- 13Cr / Super-13Cr stainless: Qualified for some mild-sour wells but cracks unpredictably above ~15 psi H₂S; the industry has shifted to nickel CRAs for new construction.
Mechanical Property Spec for Downhole Bolting
| Property | Specification (Aged Condition) |
|---|---|
| Tensile Strength | 165 ksi (1140 MPa) min |
| 0.2% Yield Strength | 110 ksi (760 MPa) min |
| Elongation in 4D | 18% min |
| Reduction of Area | 25% min |
| Hardness | 32–35 HRC |
| Charpy V-Notch at -46°C | 40 J min (NACE sour service) |
| Charpy V-Notch at -101°C | 27 J min (API 6A PSL-3G cryogenic) |
See full mechanical properties page for elevated-temperature data, Charpy envelope and comparison vs adjacent alloys.
Operating Considerations
Galvanic compatibility: Incoloy 925 is more noble than carbon steel and 13Cr but less noble than super-duplex stainless and Inconel 625. In bolted joints between Incoloy 925 and lower-grade tubulars, the galvanic effect is small in fresh / completion fluids but accelerates in aerated produced water. Where galvanic risk is a design driver, isolation gaskets are specified.
Threading and connections: Most downhole connections are API rotary-shouldered (NC-26 to NC-77) with cold-rolled threads; thread compound per API RP 7A1 (sulfide-free, nickel-alloy-compatible). Premium connections (VAM, Tenaris, Hydril) are available in Incoloy 925 by license arrangement.
Heat treatment status: All downhole bolting is supplied in the SOLUTION-ANNEALED + AGED condition (per heat-treatment specification) with full furnace charts on the MTC. Annealed-only condition is supplied only when the customer plans field re-ageing, rare in oilfield service.
Frequently Asked Questions
Is Incoloy 925 qualified for HPHT (high-pressure / high-temperature) wells? Yes, within the NACE Table A.10 envelope (1000 psi H₂S, 400°F). For HPHT wells exceeding 400°F bottom-hole, project-specific qualification testing is required per ISO 15156-3 Annex B; Special Metals C-ring data shows no SSC at 350°F up to 46 HRC, supporting safe extension beyond the standard envelope with proper qualification.
Can Incoloy 925 be used for production tubing? Yes, production tubing in Incoloy 925 is manufactured ASTM B983 (seam-welded from strip) or by extrusion + cold-pilger reduction (seamless). Sizes 2-3/8" to 7-5/8" OD, wall thicknesses to 0.5". The cost premium vs 13Cr or 22Cr duplex limits use to high-H₂S sour wells where the alternative is failure within service life.
How does Incoloy 925 compare to Inconel 725 for downhole tubing? Inconel 725 (UNS N07725) has higher strength (150 ksi YS aged vs 110 ksi for 925) and a similar sour-service envelope. 725 is preferred for ultra-deep wells where every ksi of yield matters; 925 is preferred for cost-effective coverage of typical sour-service applications. See Incoloy 925 vs Inconel 718/725 for full comparison.
What MTC certificates does TorqBolt issue? EN 10204 3.1 (manufacturer's) is the default for all downhole bolting and components. EN 10204 3.2 (third-party witnessed) on request, we work with DNV, Bureau Veritas, Lloyd's, ABS, TUV. NACE MR0175 stamping included on every sour-service order.
Related Application Pages
- Incoloy 925 in sour service, NACE MR0175 / ISO 15156
- Incoloy 925 in surface safety valves (SSV / SSSV)
- Incoloy 925 tool joints, drill string subs
- Incoloy 925 tubing & casing hangers
- Incoloy 925 marine & offshore applications
Request a Quote
For Incoloy 925 downhole components with full MTC documentation:
- Email: info@torqbolt.com
- WhatsApp: +91-22-66157017
- Datasheet PDF + sample MTC available on request
Specify component type (stud bolts, heavy hex nuts, hex bolts, tubing, machined parts), size range, quantity, applicable standards (API 6A, API 11D1, API 14A, NACE MR0175, ISO 15156), well environment (BHT, BHP, H₂S / CO₂ / chloride), and any special qualification requirements (HPHT project, NACE TM0177 C-ring, third-party witness).
References: Special Metals Corporation: INCOLOY® alloy 925 Technical Bulletin, Tables 8 (NACE C-ring), 9 (high-temperature sour SCC), 10 (free-sulfur corrosion). ASTM B805 + ASTM B983. API Spec 6A; API 11D1 (packers); API 14A (SSSV); API 5CRA (CRA tubing). NACE MR0175 / ISO 15156-3 Table A.10. INCOLOY® is a registered trademark of Special Metals Corporation.
