Alloy 945X is a high-strength, age-hardenable, corrosion-resistant nickel-iron-chromium alloy with additions of molybdenum, copper, niobium, titanium and aluminium. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
Introduced in 2011 as a higher-strength version of alloy 945, Alloy 945X carries a raised nickel content (about 54%, versus roughly 47% for alloy 945) and an optimised chemistry that increase strength and microstructural stability for the most demanding oil-and-gas environments. Its nickel content resists chloride-induced stress-corrosion cracking; nickel with molybdenum and copper gives outstanding resistance to reducing media; molybdenum and niobium add resistance to pitting and crevice corrosion; and chromium provides resistance in oxidizing environments. Niobium, titanium and aluminium drive the age-hardening reaction, forming γ′ (Ni₃(Ti,Nb,Al)) and γ″ (Ni₃Nb) precipitates that give the alloy its very high strength. It is qualified under NACE MR0175 / ISO 15156-3 and supplied in the solution-annealed and aged condition.
Typical applications include down-hole and surface well equipment for deep, sour, high-pressure / high-temperature (HPHT) wells — tubular products, valves, hangers, landing nipples, tool joints and packers — and high-strength fasteners and shafting.
| Property | Value | Unit |
|---|---|---|
| Density | 8.20 | g/cm³ |
| Melting range | 1300–1370 | °C |
| Elastic modulus | 204 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 13.0 | µm/m·°C |
| Thermal conductivity (20 °C) | 11.0 | W/m·K |
| Specific heat (20 °C) | 435 | J/kg·K |
| Structure | Austenitic (FCC) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | 50.0 | 56.0 | Austenite former; chloride-SCC resistance; γ′ matrix |
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 19.5 | 23.0 | Oxidation / pitting resistance |
| Molybdenum | Mo | 3.00 | 4.00 | Pitting / crevice / reducing-acid resistance |
| Niobium | Nb (+Ta) | 2.50 | 3.50 | γ′ / γ″ (Ni₃Nb) precipitation strengthening |
| Copper | Cu | 1.50 | 3.00 | Resistance to reducing chemicals |
| Titanium | Ti | 0.50 | 2.50 | γ′ (Ni₃Ti) precipitation strengthening |
| Aluminium | Al | — | 0.70 | γ′ formation |
| Carbon | C | — | 0.03 | Residual |
Solution-annealed and aged condition, typical values for UNS N09946 (high-strength grade).
| Condition | Property | Value |
|---|---|---|
| Solution annealed & aged | Tensile strength (UTS) | ≥1170 MPa (170 ksi) |
| Solution annealed & aged | 0.2% yield strength | ≥965 MPa (140 ksi) |
| Solution annealed & aged | Elongation at break | ≥18 % |
| Solution annealed & aged | Reduction of area | ≥35 % |
| Solution annealed & aged | Hardness | ≤42 HRC |
Confirm against the mill test report. Minimum-yield grades to 160 ksi are available; the hardness limit and microstructure are controlled for sour-service qualification.
| Environment | Performance | Notes |
|---|---|---|
| Sour gas (H₂S / CO₂) | Excellent | Qualified to NACE MR0175 / ISO 15156-3 |
| Chloride stress-corrosion cracking | Excellent | High nickel content (~54%) |
| Pitting / crevice corrosion | Excellent | Molybdenum + niobium bearing |
| Reducing media | Excellent | Ni + Mo + Cu |
| Sulfide stress cracking (SSC) | Excellent | Resistant; extreme HPHT sour-well service |
The alloy resists general corrosion, pitting, crevice corrosion, stress-corrosion cracking and sulfide stress cracking in both reducing and oxidizing environments, and the raised nickel content makes it well suited to the most aggressive deep, sour, high-pressure / high-temperature wells.
An age-hardenable corrosion-resistant alloy; strengthened by solution annealing followed by two-step ageing.
Solution Treatment Solution anneal at approximately 982–1065 °C, soak about 1.5–4 hours, and cool (air or water quench).
Precipitation Hardening (Ageing) Age at approximately 677–732 °C (1250–1350 °F) for 4–9 hours, furnace cool to about 599–643 °C (1110–1190 °F), hold for a total ageing time of at least 12 hours, then air cool or water quench — precipitating γ′ (Ni₃(Ti,Nb,Al)) and γ″ (Ni₃Nb). The schedule meets the requirements of NACE MR0175.
Good weldability; welding is performed in the solution-annealed condition with post-weld ageing. Matching or compatible nickel-alloy fillers are used.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching or compatible nickel-alloy filler |
| GMAW / MIG | Good | Compatible filler |
| EBW / laser | Good | Autogenous or matching filler |
Weld in the solution-annealed condition; apply post-weld solution and ageing to develop properties.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Solution-annealed for machining, then age |
| Machinability | Difficult; rigid setups, carbide tooling, slow speeds |
| Coolant | Ample coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | In the annealed condition; work-hardens |
| Hot forming | Readily forged; solution and age afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Oil & gas (downhole) | Tubulars, hangers, landing nipples, packers | Very high strength + sour-service resistance |
| Oil & gas (surface) | Valves, tool joints, wellhead components | Strength + H₂S / CO₂ resistance |
| Extreme HPHT wells | Deep high-pressure / high-temperature hardware | Strength + SSC / SCC resistance |
| Subsea / marine | Fasteners, shafting | Strength + corrosion resistance |
| Product Form | Standard | Notes |
|---|---|---|
| Bar, rod and forging stock | ASTM B637 · API 6A | UNS N09946 |
| Hollow bar and tube | UNS N09946 | Sour-service product |
| Plate and forged flat | UNS N09946 | — |
| Sour-service qualification | NACE MR0175 / ISO 15156-3 | HPHT sour wells |
High-nickel age-hardenable nickel-iron-chromium alloy with Mo, Cu, Nb, Ti and Al. UNS N09946.
| Alloy | Ni % | Strengthening | Yield Strength | Best Used For |
|---|---|---|---|---|
| Alloy 945X | ~54 | γ′ + γ″ (Nb, Ti, Al) | 140–160 ksi | Higher-strength 945; extreme HPHT sour oil & gas wells |
| Alloy 945 | ~47 | γ′ + γ″ (Nb, Ti, Al) | 125–160 ksi | High-strength sour-service Ni-Fe-Cr alloy |
| Alloy 925 | 42–46 | γ′ (Al, Ti) | ~110 ksi | Age-hardened 825; sour service, lower strength |
| Alloy 725 | 55–59 | γ′ + γ″ (Nb, Ti) | ~120 ksi | Age-hardened 625; sour service |
| Alloy 718 | 50–55 | γ′ + γ″ (Nb, Ti) | ~150 ksi | Most-used high-strength superalloy |




