What Is a Seamless Incoloy 925 Tube?
Seamless Incoloy 925 Tube — UNS N09925 — is the age-hardenable member of the 825 family: a nickel–iron–chromium alloy with molybdenum, copper and elevated titanium/aluminum additions (Ti 1.90–2.40%, Al 0.10–0.50%), produced to ASTM B983 from a solid billet with no weld seam.
Two-step heat treatment — solution anneal at 996–1024 °C followed by aging at 740 °C — precipitates gamma-prime and lifts yield strength to 758 MPa (110 ksi) minimum — roughly triple the annealed 825 value — while the base chemistry keeps the acid and chloride corrosion behavior. With hardness capped at 38 HRC and density 8.08 g/cm³, 925 is the standard choice for high-strength sour-service tubulars in oil and gas.
Size Range: OD 6–257 mm · WT 0.5–35 mm
Key Features and Advantages
Seamless UNS N09925 tube pairs 825-family corrosion resistance with precipitation-hardened strength:
High Strength with Corrosion Resistance: yield 758 MPa (110 ksi) minimum and tensile 965 MPa (140 ksi) minimum after age hardening, with 825-like corrosion behavior.
Sour Service Proven: 38–46% Ni with Mo and Cu resists H2S, CO2 and chloride environments; widely used under NACE MR0175/ISO 15156.
Hardness Ceiling Built In: 38 HRC maximum per ASTM B983 Table 3 suits sour-service component requirements.
Resistance to Localized Attack: 19.5–23.5% Cr and 2.50–3.50% Mo guard against pitting and crevice corrosion.
Controlled Age-Hardening Response: titanium 1.90–2.40% with aluminum 0.10–0.50% and Nb ≤0.50% give a repeatable strengthening window.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for UNS N09925 seamless tube.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N09925 | Incoloy 925 | Not listed in grade index | Not listed in grade index | Not listed in grade index | NS2401 |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
the gamma-prime strengthened nickel–iron–chromium matrix delivers the property mix.
| Grade | Ni | Cr | Fe | Mo | Cu | Ti | Al | Nb | Mn | C | Si | S | P |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UNS N09925 | 38.0–46.0 | 19.5–23.5 | 22.0 min | 2.50–3.50 | 1.50–3.00 | 1.90–2.40 | 0.10–0.50 | ≤0.50 | ≤1.00 | ≤0.03 | ≤0.50 | ≤0.030 | ≤0.030 |
Chemical requirements per ASTM B983-21, Table 1. Single values are maximum content unless a range or minimum is indicated. No phosphorus limit is specified (shown as –); iron is determined arithmetically by difference (22.0% minimum); columbium (Nb) 0.50% max.
Typical Mechanical Properties
Values below are specification minimums for the delivery condition; they define the acceptance basis for UNS N09925 seamless tube.
| Condition | Tensile Strength, min, ksi (MPa) | Yield Strength, min, ksi (MPa) | Elongation in 2 in. or 4D, min, % | Hardness, max |
|---|---|---|---|---|
| Solution annealed + precipitation hardened | 140 (965) | 110 (758) | 18 | ≤38 HRC |
Mechanical properties per ASTM B983-21, Table 3, in the solution annealed plus precipitation hardened condition. The high strength comes from the two-step heat treatment per Table 2 (see Manufacturing Process below).
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably across a range of environments.
| Density | Melting Range | Thermal Expansion | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|
| 8.08 g/cm3 (ASTM B983) | 1311 – 1366 °C | 13.2 μm/m·°C (20–100°C) | 199 GPa | 1.17 μΩ·m |
Size Tolerance Chart (mm)
Permissible variations for seamless nickel alloy tube in accordance with ASTM B983-21, Table 4:
| Outside Diameter, mm | Permissible Variation in OD, mm | Average Wall, % | Minimum Wall |
|---|---|---|---|
| 19 to 38, incl | +0.4 / −0.8 | ±12.5 | +28.5% / −0 |
| over 38.1 to 102, incl | ±0.8 | ±12.5 | +28.5% / −0 |
| over 102 to 235, incl | +1.6 / −0.8 | ±12.5 | +28.5% / −0 |
| over 235 to 305, incl | ±2.8 | ±12.5 | – |
Notes (ASTM B983-21, Table 4, hot-finished tube): for tube 5 in. (127 mm) and under in OD, the OD tolerance applies to individual measurements and includes ovality; for tube over 5 in. OD, the mean OD shall conform to the table and individual measurements shall not exceed twice the permissible variations. Wall variations apply to the wall as ordered (minimum or average), but not to both.
Length Tolerance
- Dimensions, straightness and length for cut lengths are governed by the general requirements of ASTM B829 (referenced by ASTM B983-21, 14.2).
- Tube is normally supplied in mill lengths or specific cut lengths as agreed in the order.
Disclaimer: Dimensional data above are summarized from ASTM B983-21, Table 4. The full and most current specification document must always be consulted for official design and procurement purposes.
Common Industrial Applications
The combination of corrosion resistance, mechanical strength and manufacturing quality makes UNS N09925 seamless tube a preferred choice for:
Downhole and Surface Gas Well Components
Tubing, hangers, landing nipples, tool joints and packers in high-strength sour wells.
Valves, Fittings and Fasteners
High-strength pressure-retaining components for H2S-containing streams.
Marine and Seawater Systems
High-strength tubing where seawater corrosion resistance is required.
High-Strength Process Lines
Piping and instrumentation lines combining pressure load with corrosive media.
Frequently Asked Questions
What sizes are available for Incoloy 925 seamless tube?
Which specification governs Incoloy 925 seamless tube?
What inspection documents are provided?
Technical review: page data reviewed by the Xinzhe technical desk on 2026-09-27. Property values are typical reference data compiled from Special Metals Corporation alloy data sheets and the governing ASTM specifications; they are not acceptance guarantees unless stated in the purchase order. “Incoloy” is a trademark of Special Metals Corporation, used here to identify the alloy family only.
Ready to Request a Quotation?
Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
