Inconel 706 is a precipitation-hardenable nickel-iron-chromium superalloy. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
A derivative of alloy 718, Inconel 706 provides high mechanical strength combined with notably good fabricability. Niobium and titanium additions drive precipitation of the gamma-prime and gamma-double-prime phases that give the alloy its high strength and creep resistance at elevated temperature, while the nickel and chromium provide stability and corrosion resistance and the iron balances the composition economically. Its strength is similar to that of alloy 718, but the alloy is more readily fabricated — particularly in large sections — owing to a lower tendency to segregation, which is why it is favoured for very large forgings. It retains useful strength to about 705 °C (1300 °F) and is used in the solution-treated and precipitation-hardened condition.
Typical applications include gas-turbine discs, shafts, spacers and rings for aerospace and land-based turbines, and other large rotating and structural components requiring high strength with good fabricability.
| Property | Value | Unit |
|---|---|---|
| Density | 8.05 | g/cm³ |
| Melting range | 1335–1370 | °C |
| Elastic modulus | 210 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 13.4 | µm/m·°C |
| Thermal conductivity (20 °C) | 12.6 | W/m·K |
| Specific heat (20 °C) | 435 | J/kg·K |
| Structure | Austenitic (FCC) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | 39.0 | 44.0 | Austenite former; γ′/γ″ matrix |
| Iron | Fe | Balance | — | Base element (~38%) |
| Chromium | Cr | 14.5 | 17.5 | Oxidation / corrosion resistance |
| Niobium | Nb | 2.50 | 3.30 | γ″ (Ni₃Nb) precipitation strengthening |
| Titanium | Ti | 1.50 | 2.00 | γ′ (Ni₃Ti) precipitation strengthening |
| Aluminium | Al | — | 0.40 | γ′ formation |
| Cobalt | Co | — | 1.00 | Residual |
| Copper | Cu | — | 0.30 | Residual |
| Manganese | Mn | — | 0.35 | Deoxidiser |
| Silicon | Si | — | 0.35 | Deoxidiser |
| Carbon | C | — | 0.06 | Carbide formation |
| Boron | B | — | 0.006 | Grain-boundary strengthening |
Solution-treated and aged condition, typical values for UNS N09706.
| Condition | Property | Value |
|---|---|---|
| Solution treated & aged | Tensile strength (UTS) | ≥1170 MPa (170 ksi) |
| Solution treated & aged | 0.2% yield strength | ≥930 MPa (135 ksi) |
| Solution treated & aged | Elongation at break | ≥12 % |
| Solution treated & aged | Reduction of area | ≥15 % |
| — | Elastic modulus | 210 GPa |
Confirm against the mill test report. Properties depend on the solution and multi-step ageing treatment selected.
| Environment | Performance | Notes |
|---|---|---|
| High-temperature oxidation | Good | To about 705 °C service |
| Aqueous / general | Good | Chromium-bearing |
| Carburising / sulfidising | Moderate | Lower Cr than 600/690 |
| Stress-corrosion cracking | Good | Generally resistant |
| Elevated-temperature strength | Excellent | Primary design advantage |
Corrosion and oxidation resistance is good for its class; the alloy is selected primarily for high-temperature strength and fabricability rather than corrosion service.
A precipitation-hardenable superalloy; strengthened by solution treatment followed by multi-step ageing.
Solution Treatment Solution anneal at approximately 925–1010 °C and cool in air. A higher solution temperature is used where creep-rupture performance is the priority.
Precipitation Hardening (Ageing) Age in two or three steps, for example approximately 840 °C / 3 h, then 720 °C / 8 h, then furnace cool and hold near 620 °C, air cool — precipitating γ′ (Ni₃Ti) and γ″ (Ni₃Nb). The ageing schedule is selected to balance tensile, creep-rupture and notch properties.
Good weldability, better than many γ′-strengthened superalloys; welding is done in the solution-annealed condition followed by post-weld heat treatment and ageing.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching or alloy 718-type filler |
| GMAW / MIG | Good | Matching filler |
| EBW / laser | Good | Autogenous or matching filler |
Weld in the solution-annealed condition; apply post-weld solution and ageing treatment 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 — a key advantage for large discs |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aero gas turbine | Discs, shafts, spacers, rings | High strength + fabricability |
| Land-based turbine | Large rotor discs and forgings | Large-section strength + low segregation |
| Power generation | High-temperature rotating parts | Creep + tensile strength to ~705 °C |
| Aerospace structures | Highly stressed forgings | Strength + toughness |
| Product Form | ASTM Standard | AMS |
|---|---|---|
| Bar and forging stock | ASTM B637 | AMS 5701 / 5702 / 5703 |
| Forgings | ASTM B637 | AMS 5705 |
| Billet | — | AMS 5704 |
| Material designation | UNS N09706 | — |
Nickel-iron-chromium precipitation-hardenable superalloy. UNS N09706.
| Alloy | Ni % | Fe % | Strengthening | Best Used For |
|---|---|---|---|---|
| Inconel 706 | 39–44 | ~38 | γ′ + γ″ (Nb, Ti) | 718-type strength, better fabricability; large turbine discs |
| Inconel 718 | 50–55 | ~18 | γ′ + γ″ (Nb, Ti) | High-strength workhorse superalloy to ~700 °C |
| Inconel X-750 | ≥70 | 5–9 | γ′ (Al, Ti) | Springs, bolts, high-temperature fasteners |
| Incoloy 907 | ~38 | Balance | γ′ (Nb, Ti) | Low-expansion gas-turbine parts |
| Inconel 625 | ≥58 | ≤5 | Solid solution | Corrosion + moderate high-temperature strength |




