Despite the similar "925 / 926" trademark numbering, Incoloy 925 (UNS N09925) and Incoloy 926 (UNS N08926, also designated W.Nr. 1.4529) are not the same alloy family and not interchangeable. Incoloy 925 is a nickel-iron-chromium age-hardenable alloy with 44% Ni and 22% min Fe, designed for sour-service oilfield bolting; gamma-prime precipitation lifts yield strength to 110 ksi minimum. Incoloy 926 is a 6% molybdenum super-austenitic stainless steel with 25% Ni and 40–45% Fe, designed for chloride-rich seawater and acid service in the solution-annealed condition only, it cannot be age-hardened and ships at ~45 ksi yield. Buyers sometimes confuse the two because both carry the INCOLOY trademark, but the chemistry, mechanical envelope and target service are entirely different.
Need to pick the right alloy? Email info@torqbolt.com with the service environment (sour gas vs seawater vs acid), required strength target, and dimensions. WhatsApp +91-22-66157017.
Chemistry Side-by-Side
| Element | Incoloy 925 (N09925) | Incoloy 926 (N08926) |
|---|---|---|
| Ni | 42–46% (high) | 24–26% (moderate) |
| Cr | 19.5–22.5% | 19–21% |
| Fe | 22% min (bal) | 40–45% (bal) |
| Mo | 2.5–3.5% | 6.0–7.0% (signature) |
| Cu | 1.5–3.0% | 0.5–1.5% |
| N | not specified | 0.15–0.25% (signature austenite stabiliser) |
| Ti | 1.9–2.4% (gamma-prime) | not specified |
| Al | 0.1–0.5% (gamma-prime) | not specified |
| C | 0.03 max | 0.020 max |
Two signature differences: (1) Incoloy 926 has 6–7% Mo (Incoloy 925 has only 2.5–3.5%), this gives 926 a much higher PREN (~43 vs ~32 for 925) and superior pitting resistance in chloride-rich seawater. (2) Incoloy 926 has 0.15–0.25% nitrogen as a primary austenite stabiliser; Incoloy 925 does not specify nitrogen. The titanium + aluminium age-hardening package is unique to 925.
Mechanical Properties
| Property | Incoloy 925 (Aged) | Incoloy 926 (Annealed) |
|---|---|---|
| Tensile Strength min | 165 ksi (1140 MPa) | 94 ksi (650 MPa) |
| 0.2% Yield Strength min | 110 ksi (760 MPa) | 43 ksi (295 MPa) |
| Elongation min | 18% | 35% |
| PREN (Cr+3.3·Mo+16·N) | ~32 | ~43 |
| Strengthening | Gamma-prime Ni₃(Al, Ti) | Solid solution + N strengthening only |
Incoloy 925 has 2.5× the yield strength of 926 because of age hardening. Incoloy 926 wins on PREN (and thus pitting resistance) because of higher Mo + N. Different optimisation targets, 925 prioritises strength; 926 prioritises chloride pitting resistance.
Service Envelope, Where Each Alloy Wins
| Service | Recommended Alloy | Reason |
|---|---|---|
| API 6A wellhead bolting (sour H₂S) | Incoloy 925 | Only 925 meets 110 ksi YS + qualified to 1000 psi H₂S |
| Severe-chloride seawater (FPSO, swimming-pool covers, brine handling) | Incoloy 926 | Higher PREN ~43 vs ~32; pitting / crevice in chloride is the failure mode |
| Sulfuric acid + chloride mixed environments (FGD, scrubbers) | Incoloy 926 | 6Mo + N package designed for these mixed environments |
| Sour-service production tubing (high strength) | Incoloy 925 | Strength + sour-service envelope match |
| Subsea production manifold body (corrosion + strength) | Incoloy 925 (typically) or 6Mo SS | Application-specific, depends on H₂S level |
| Heat exchanger tubing in seawater | Incoloy 926 or titanium | Very high chloride pitting performance |
Sour-Service Qualification
Incoloy 925 is qualified under NACE MR0175 / ISO 15156-3 Table A.10 for sour service up to 1000 psi H₂S, 400°F, with a 35 HRC hardness cap. Incoloy 926 is NOT specifically listed in MR0175 Table A, it is a 6Mo super-austenitic stainless steel rather than a nickel alloy and falls under different sour-service qualification logic (typically not used in significant H₂S service because cost-effective alternatives exist for chloride-only and oilfield-only applications). The two alloys serve different industries.
Frequently Asked Questions
Why are 925 and 926 numbered consecutively if they are different alloy families? The numbering is historical, Special Metals assigned trademark numbers as alloys were developed without enforcing a chemistry-family pattern. The "925" and "926" numbers are sequential by trademark registration, not by composition. Buyers should always work from the UNS designation (N09925 vs N08926) rather than the trademark number to avoid confusion.
Can Incoloy 926 be substituted for 304L or 316L in chloride service? Yes, Incoloy 926 is the high-PREN replacement for 304L (PREN ~19) and 316L (PREN ~25) where chloride pitting has been the historical failure mode. The cost premium is ~3× vs 316L but the corrosion lifetime improvement is typically 5–10×. Not a substitute for sour-service bolting, that requires Incoloy 925 or stronger.
Are 925 and 926 covered by the same ASTM specification? No. Incoloy 925 is covered by ASTM B805 (bar / forgings) and ASTM B983 (sheet, plate, strip). Incoloy 926 is covered by ASTM A240 (plate, sheet, strip), ASTM A276 (bar) and ASTM A312 (welded pipe), the stainless-steel specification family rather than the nickel-alloy family.
Can the two alloys be welded together? Yes, with INCONEL Filler Metal 625 (NiCrMo solid-solution filler). The dissimilar joint requires careful heat-input control to avoid HAZ over-ageing on the 925 side. Post-weld heat treatment is impractical because the two alloys have different anneal temperatures (925: 1900°F; 926: 2050°F), the dissimilar weld is therefore typically left in the as-welded condition with reduced design allowables.
Compare Incoloy 925 to Other Alloys
- Inconel vs Incoloy, What's the difference?
- Incoloy 925 vs Inconel 718, gamma-prime vs gamma double-prime
- Incoloy 925 vs Incoloy 825, age-hardenable vs solid solution
- Incoloy 925 vs Monel K-500, nickel-Fe-Cr vs nickel-Cu
- Incoloy 925 vs Duplex 2205, nickel CRA vs duplex stainless
Request a Quote
For Incoloy 925 with full MTC, or for help selecting between 925 and a 6Mo super-austenitic alternative:
- Email: info@torqbolt.com
- WhatsApp: +91-22-66157017
- Datasheet PDF + sample MTC available on request
Specify product type, size, quantity, applicable standards (ASTM B805, ASTM A240/A276 for 6Mo SS, API 6A, NACE MR0175), service medium (sour gas / seawater / acid mix) and required mechanical envelope.
References: ASTM B805 (UNS N09925); ASTM A240 / A276 (UNS N08926). Special Metals Corporation: INCOLOY® alloy 925 + INCOLOY® alloy 926 product literature. NACE MR0175 / ISO 15156-3. INCOLOY® is a registered trademark of Special Metals Corporation.
