Inconel 783 is an oxidation-resistant, low-expansion nickel-cobalt-iron alloy with aluminium, chromium and niobium additions. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
One of the newest high-performance superalloys developed by Special Metals (US Patent 5,478,417), Inconel 783 is a three-phase age-hardenable alloy in which the high aluminium content forms not only the gamma-prime (γ′) phase but also a beta (β, NiAl) aluminide phase in the austenitic matrix. This structure can be processed to resist both stress-accelerated grain-boundary oxidation (SAGBO) and general oxidation while providing a low coefficient of thermal expansion — about 20% lower than that of alloy 718 — and useful mechanical properties up to about 700 °C. It shows excellent resistance to oxidation in cyclic tests at temperatures up to and beyond 704 °C (1300 °F), and SAGBO resistance comparable to alloy 718. It is supplied in the solution-treated and aged condition.
Typical applications include aircraft gas-turbine containment and clearance-control components — rings, casings, shrouds and seals for compressors, turbines and exhaust systems.
| Property | Value | Unit |
|---|---|---|
| Density | 7.81 | g/cm³ |
| Melting range | 1380–1430 | °C |
| Elastic modulus | 152 | GPa |
| Coefficient of thermal expansion (20–540 °C) | 9.5 | µm/m·°C |
| Thermal conductivity (20 °C) | 12.0 | W/m·K |
| Specific heat (20 °C) | 435 | J/kg·K |
| Structure | Austenitic (FCC) + β-NiAl | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Cobalt | Co | Balance | — | Base element |
| Nickel | Ni | 26.0 | 30.0 | Matrix; γ′ / β former |
| Iron | Fe | 24.0 | 27.0 | Low-expansion matrix |
| Aluminium | Al | 5.0 | 6.0 | γ′ and β (NiAl) formation; oxidation resistance |
| Niobium | Nb | 2.5 | 3.5 | γ′ precipitation strengthening |
| Chromium | Cr | 2.5 | 3.5 | Oxidation resistance |
| Carbon | C | — | 0.03 | Carbide formation |
| Boron | B | 0.003 | 0.012 | Grain-boundary strengthening |
Solution-treated and aged condition, typical values for UNS R30783.
| Condition | Property | Value |
|---|---|---|
| Solution treated & aged | Tensile strength (UTS) | ≥1000 MPa (145 ksi) |
| Solution treated & aged | 0.2% yield strength | ≥690 MPa (100 ksi) |
| Solution treated & aged | Elongation at break | ≥15 % |
| Solution treated & aged | Reduction of area | ≥20 % |
| — | Elastic modulus | 152 GPa |
Confirm against the mill test report. The alloy retains useful mechanical properties up to about 700 °C with a coefficient of thermal expansion about 20% below that of alloy 718.
| Environment | Performance | Notes |
|---|---|---|
| High-temperature oxidation (cyclic) | Excellent | Aluminium-rich; to and beyond 704 °C |
| SAGBO (stress-accelerated GB oxidation) | Excellent | Comparable to alloy 718, better than 909 |
| Oxygen embrittlement | Very Good | Resistant; notch ductility retained |
| Aqueous / general | Good | Moderate chromium |
| Low thermal expansion | Excellent | ~20% lower than alloy 718 |
The high aluminium content provides excellent resistance to general oxidation and to stress-accelerated grain-boundary oxidation while maintaining a low coefficient of thermal expansion — the combination sought for gas-turbine clearance-control hardware.
A three-phase (γ′ + β) age-hardenable alloy; strengthened by solution treatment followed by beta ageing and precipitation ageing.
Solution Treatment Solution anneal at approximately 1121 °C (2050 °F) for about 1 hour and air cool.
Precipitation Hardening (Ageing) Beta-age at approximately 845 °C (1550 °F) for 4 hours and air cool, then age at approximately 720 °C (1325 °F) for 8 hours, furnace cool at about 55 °C/h to 620 °C (1150 °F), hold 8 hours and air cool — precipitating γ′ and the β (NiAl) phase.
Good weldability; the alloy can be formed, machined and welded using the conventional procedures for nickel alloys, in the solution-annealed condition with post-weld ageing.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching alloy 783 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 | Rough machine annealed, then age, then finish |
| 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 | ~927–1121 °C (1700–2050 °F); solution and age afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aero gas turbine | Containment rings, casings | Low expansion + oxidation resistance |
| Turbine / compressor | Shrouds, seals, clearance-control parts | Dimensional stability + SAGBO resistance |
| Exhaust systems | Rings and seals | Oxidation resistance to >704 °C |
| Aerospace | Clearance-control hardware | Low CTE + useful strength to 700 °C |
| Product Form | Standard / Designation | Notes |
|---|---|---|
| Forging billet | AMS 5940 | UNS R30783 |
| Rod and bar (machining) | UNS R30783 | Special Metals product |
| Extruded section and wire rod | UNS R30783 | — |
| Material designation | UNS R30783 | US Patent 5,478,417 |
Oxidation-resistant low-expansion nickel-cobalt-iron alloy. UNS R30783.
| Alloy | Type | CTE Trend | Strengthening | Best Used For |
|---|---|---|---|---|
| Inconel 783 | Ni-Co-Fe + Al | Low (~20% < 718) | γ′ + β (NiAl) | Low-expansion, oxidation-resistant; gas-turbine clearance control |
| Incoloy 909 | Fe-Ni-Co | Very low | γ′ (Nb, Ti) | Low-expansion gas-turbine parts |
| Incoloy 907 | Fe-Ni-Co | Very low | γ′ (Nb, Ti) | Low-expansion rings and shafts |
| Inconel 718 | Ni-Cr-Fe | Standard | γ′ + γ″ (Nb, Ti) | Most-used high-strength superalloy |
| Inconel X-750 | Ni-Cr | Standard | γ′ (Al, Ti) | Springs, bolts, high-temperature fasteners |




