Seamless rolled rings, discs, shafts, sleeves, seal rings and turbine casings forged to order in Alloy 783, the oxidation-resistant, low-thermal-expansion Ni-Co-Fe superalloy used for gas turbine clearance control.
Alloy 783 (UNS R30783), also sold as Inconel 783 and designated GH6783 in China, is an age-hardenable nickel-cobalt-iron superalloy containing roughly 28% nickel, 34% cobalt, 26% iron, 5.5% aluminium, 3% niobium and 3% chromium. Its coefficient of thermal expansion is about 20% lower than Inconel 718, and its high aluminium content forms a protective alumina scale that resists oxidation and stress-accelerated grain-boundary oxidation at temperature. Gas turbine designers use that combination to hold tighter running clearances, which raises power output and fuel efficiency.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China that produces Alloy 783 forgings to customer drawings: seamless rolled rings, discs and blanks, stepped shafts, hollow sleeves and bushings, blocks and plates, turbine seal rings, shrouds and casing sections, supplied rough-machined or finish-machined with EN 10204 3.1 or 3.2 certification. Enquiries: 0086-189-2135-9659 · sales@steelforgepieces.com.
Alloy 783 is a precipitation-hardening superalloy built on a nickel-cobalt-iron base rather than the nickel-chromium base used by most heat-resistant alloys. Chromium is held down to 2.5-3.5% because chromium raises thermal expansion. Oxidation protection comes instead from 5-6% aluminium, which forms a tenacious alumina scale. The alloy was developed by Special Metals Corporation and is protected by U.S. Patent 5,478,417.
Strengthening comes from three phases working together: the γ′ Ni3(Al,Nb,Ti) precipitate, a grain-boundary β-NiAl phase, and the solid-solution matrix itself. The β-NiAl at the grain boundaries is what gives Alloy 783 its resistance to SAGBO, the notch-sensitivity failure mode that limits earlier low-expansion alloys such as Incoloy 909 in oxidising service.
| System | Designation | Notes |
|---|---|---|
| UNS | R30783 | Primary unified number |
| Trade name | INCONEL® alloy 783 | Special Metals Corporation |
| Common usage | Alloy 783 · Inconel 783 · IN 783 | Used interchangeably in enquiries |
| China (GB) | GH6783 | Chinese high-temperature alloy designation |
| AMS | AMS 5940 | Forging billet |
| Patent | US 5,478,417 | Original alloy patent |
Naming note: INCONEL and INCOLOY are registered trademarks of Special Metals Corporation. Jiangyin Jiangnan Metal Co., Ltd. is an independent forging factory and uses these names only to identify the chemistry a customer has specified.
Cobalt is the balance element and typically lands near 34%. Every heat we forge is supplied with a certified ladle analysis and, on request, a product analysis taken from the forging itself.
| Element | Symbol | Min | Max | Nominal |
|---|---|---|---|---|
| Nickel | Ni | 26.0 | 30.0 | 28.5 |
| Cobalt | Co | Balance | 34.0 | |
| Iron | Fe | 24.0 | 27.0 | 25.5 |
| Aluminium | Al | 5.0 | 6.0 | 5.4 |
| Chromium | Cr | 2.5 | 3.5 | 3.0 |
| Niobium | Nb | 2.5 | 3.5 | 3.0 |
| Titanium | Ti | 0.1 | 0.4 | 0.3 |
| Boron | B | 0.003 | 0.012 | 0.005 |
| Carbon | C | - | 0.03 | 0.02 |
| Manganese | Mn | - | 0.50 | - |
| Silicon | Si | - | 0.50 | - |
| Copper | Cu | - | 0.50 | - |
| Phosphorus | P | - | 0.015 | - |
| Sulfur | S | - | 0.005 | - |
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.81 g/cm³ | 0.282 lb/in³ |
| Melting range | 1336-1407 °C | 2437-2565 °F |
| Specific heat | 455 J/kg·°C at 25 °C | 0.109 Btu/lb·°F at 77 °F |
| Modulus of elasticity | ≈144 GPa at 560 °C | ≈20.9 × 10³ ksi at 1040 °F |
| Mean CTE (indicative) | ≈12.2 × 10⁻⁶ /°C to 560 °C | ≈6.8 × 10⁻⁶ /°F to 1040 °F |
| Max useful temperature | ≈704 °C | ≈1300 °F |
| Crystal structure | FCC γ matrix with γ′ and grain-boundary β-NiAl | |
| Magnetic response | Ferromagnetic at room temperature | |
Thermal expansion needs one caveat. Like other Invar-type materials, Alloy 783 has an inflection temperature above which expansion climbs steeply toward normal alloy behaviour. Below the inflection the CTE is very low; above it the advantage narrows. Design against a CTE curve for your actual operating band rather than a single averaged number.
Alloy 783 develops high room-temperature strength in the aged condition and holds a useful share of it to about 704 °C (1300 °F). The values below are typical for bar and forgings given the standard three-step heat treatment described in the next section.
| Test temperature | UTS | 0.2% yield | Elongation |
|---|---|---|---|
| 20 °C / 68 °F | 1140-1250 MPa | 790-890 MPa | 15-22% |
| 427 °C / 800 °F | 1030-1120 MPa | 700-800 MPa | 15-22% |
| 560 °C / 1040 °F | - | ≈630 MPa | - |
| 649 °C / 1200 °F | 930-1030 MPa | 620-720 MPa | 12-20% |
| 704 °C / 1300 °F | 830-950 MPa | 580-680 MPa | 12-20% |
Note on these figures: they are typical published values for orientation and quotation, not specification minimums and not acceptance criteria. Section size, forging reduction, grain flow direction and test specimen location all shift results. Tell us the specification you are buying to, whether AMS 5940, a customer standard or your own drawing, and we will forge, heat treat and test to that document and report the certified numbers.
Alloy 783 reaches its published properties only after a three-stage schedule: solution anneal, a high-temperature beta age that precipitates the grain-boundary β-NiAl phase, then a two-step age that develops the γ′ strengthening precipitate. The slow furnace cool between the two ageing holds controls the size distribution of the γ′ precipitate and cannot be shortened.
| Stage | Temperature | Hold | Cooling |
|---|---|---|---|
| 1. Solution anneal | 1121 °C / 2050 °F | 1 hour | Air cool |
| 2. Beta age | 845 °C / 1550 °F | 4 hours | Air cool to room temperature |
| 3a. Age harden | 718 °C / 1325 °F | 8 hours | Furnace cool at 55 °C/h (100 °F/h) |
| 3b. Second age | 621 °C / 1150 °F | 8 hours | Air cool |
The practical hot-working window for Alloy 783 runs from about 927 °C to 1121 °C (1700-2050 °F). We plan forging passes to keep the workpiece inside that band, with reheats scheduled so the final reduction still occurs above the lower limit. Finishing too cold is the usual cause of a rejected superalloy forging.
These three alloys compete for the same turbine hardware, and the choice usually comes down to how much thermal growth the design can tolerate against how much oxidation the part will see.
| Criterion | Alloy 783 | Inconel 718 | Incoloy 909 |
|---|---|---|---|
| UNS | R30783 | N07718 | N19909 |
| Base system | Ni-Co-Fe | Ni-Cr-Fe | Fe-Ni-Co |
| Thermal expansion | Low, about 20% below 718 | Baseline | Lowest of the three |
| Oxidation resistance | Excellent (alumina scale) | Excellent (chromia scale) | Poor, coating usually needed |
| SAGBO / notch sensitivity | Resistant | Resistant | Susceptible |
| Room-temp strength | High | Highest | Moderate |
| Density | 7.81 g/cm³ | 8.19 g/cm³ | 8.30 g/cm³ |
| Forgeability | Comparable to 718 | Well established | More restrictive |
| Relative cost | High (cobalt content) | Moderate | Moderate |
| Typical choice when | Clearance control in oxidising air | Maximum strength matters most | Lowest expansion, protected environment |
Choose Inconel 718 when strength dominates, Incoloy 909 when expansion dominates and the part is protected, and Alloy 783 when a component needs both low expansion and bare-metal oxidation resistance. Jiangyin Jiangnan Metal forges all three. See Inconel 718 forgings and the full nickel alloy index.
Jiangyin Jiangnan Metal Co., Ltd. forges Alloy 783 to customer drawings on open-die presses and radial-axial ring mills. Everything below is made to order. There is no stock catalogue for this grade, because superalloy forgings are bought against a drawing and a specification.
Most forging shops in China buy superalloy billet from a third party, which is what drives cost and lead time on grades like this one. Alloy 783 is melted here. The chemistry is aimed at the forging it will become, and the certificate traces back to a melt number rather than to a purchased billet.
| Furnace | Capacity | Role for this grade |
|---|---|---|
| Vacuum induction melting (VIM) | 3 t | Primary melt; controls aluminium, niobium and titanium recovery and gas content |
| Vacuum arc remelting (VAR) | 6 t | Second melt for VIM + VAR double-melt specifications |
| Electroslag remelting (IGESR) | 3 t and 6 t | Protective atmosphere; alternative or third melt for ingot cleanliness |
| High-temperature car-bottom furnace | 3500 x 1300 x 1100 mm, 3 off | Solution anneal at 1121 °C and both ageing steps |
The envelope below is the plant limit, set by the presses, ring mills and machine tools. For Alloy 783 the binding constraint usually sits further upstream: superalloy ingot comes from the 3 t vacuum induction furnace and the 6 t remelting furnaces, so practical single-piece weight for this grade follows ingot size rather than press capacity. Solution annealing is limited to the 3500 x 1300 x 1100 mm working chamber of the high-temperature furnaces.
| Product form | Envelope | Set by |
|---|---|---|
| Seamless rolled rings | OD 50-6000 mm | 1 m, 3 m and 6 m radial-axial ring mills |
| Forged rings | Sections outside the ring-mill range | Upset and punch route |
| Discs, blocks and plates | to 5000 mm diameter machined | 5000 mm swing vertical turning lathe |
| Round, square and flat bars | to 1600 mm diameter | CNC lathe, 1600 x 3300 mm |
| Hollow bars, sleeves and bushings | to 1600 x 10000 mm bored | CNC deep-hole drilling machine |
| Shafts and stepped shafts | to 14000 mm turned length | C61160 lathe; 15 m well furnace for vertical quench |
| Cylinders, casings and shells | By drawing | Bored from solid forged blanks |
| Single piece weight, plant | 10 kg to 30000 kg | 60 t maximum heat; 6300 t press |
| Single piece weight, Alloy 783 | Governed by ingot size | 3 t VIM and 6 t VAR / ESR route |
Alloy 783 forgings go into aircraft and industrial gas turbines, steam turbines and rotating equipment where dimensional stability at temperature decides efficiency: compressor casings and shroud rings, turbine seal rings and clearance-control hardware, exhaust system components, high-temperature bolting, valve spindles and stems, and impeller and disc blanks.
Superalloy quotations stall on missing information more often than on price. Send these eight items and a firm quotation normally follows within two working days.
Alloy 783 is used for gas turbine and steam turbine components where thermal growth must be controlled: seal rings, shroud rings, compressor and turbine casings, exhaust hardware, clearance-control rings, high-temperature bolting and valve spindles. Its low coefficient of thermal expansion lets designers set tighter running clearances, which improves power output and fuel efficiency.
Yes. INCONEL alloy 783 is the trade name used by Special Metals Corporation; Alloy 783, IN 783 and UNS R30783 all refer to the same chemistry. In China the equivalent designation is GH6783. Buyers use the names interchangeably, and a forging ordered under any of them is made to the same composition limits.
The UNS number for Alloy 783 is R30783. The R3 prefix places it among cobalt-base and cobalt-bearing heat-resistant alloys, which reflects the fact that cobalt is the balance element at roughly 34% rather than nickel. Forging billet is commonly ordered to AMS 5940.
Alloy 783 contains 26.0-30.0% nickel, 24.0-27.0% iron, 5.0-6.0% aluminium, 2.5-3.5% chromium, 2.5-3.5% niobium and 0.1-0.4% titanium, with cobalt as the balance at about 34%. Carbon is held to 0.03% maximum and boron runs 0.003-0.012%. The full limiting composition is in Table 2 above.
Alloy 783 retains a useful share of its strength to about 704 °C (1300 °F), which is the normal upper limit quoted for load-bearing service. Above that temperature the γ′ strengthening precipitate begins to coarsen and the low-expansion advantage narrows. Long-term exposure also produces a small dimensional shrinkage that should be accounted for in clearance-critical designs.
The standard schedule has three stages: solution anneal at 1121 °C (2050 °F) for 1 hour and air cool; beta age at 845 °C (1550 °F) for 4 hours and air cool to room temperature; then age harden at 718 °C (1325 °F) for 8 hours, furnace cool at 55 °C per hour (100 °F per hour) to 621 °C (1150 °F), hold 8 hours and air cool.
Chromium raises the coefficient of thermal expansion, so low-expansion alloys built on Ni-Fe-Co compositions must keep it low. Alloy 783 holds chromium to 2.5-3.5%. Oxidation protection is provided instead by 5-6% aluminium, which forms a stable alumina scale. That substitution is what allows the alloy to be both low-expansion and oxidation-resistant in bare-metal service.
Yes. Alloy 783 has hot-working characteristics comparable to Inconel 718 and less restrictive than Incoloy 909, so it is routinely open-die forged and ring rolled. Jiangyin Jiangnan Metal Co., Ltd. produces seamless rolled Alloy 783 rings and discs to customer drawings, working within the 927-1121 °C (1700-2050 °F) hot-working window with scheduled reheats.
It is melted on site. The works runs a 3 t vacuum induction furnace, a 6 t vacuum arc remelting furnace and 3 t and 6 t protective-atmosphere electroslag furnaces, so VIM, VIM + VAR double-melt and VIM + ESR routes for Alloy 783 are available without subcontracting. Most forging shops in China import superalloy billet for this grade, which adds both cost and lead time.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, operating since 1997. It melts, forges, heat treats, machines and certifies Alloy 783 (UNS R30783 / GH6783) rings, discs, shafts, sleeves, blocks and casings on one site, with EN 10204 3.1 or 3.2 certification and CCS, BV, DNV, LR and NK approvals. Contact 0086-189-2135-9659 or sales@steelforgepieces.com.
The minimum order is 10 kg by weight, with no minimum piece count, so a single prototype forging is quotable. Alloy 783 is made to order rather than stocked. Normal lead time runs 20 to 60 days from order confirmation, with superalloys at the upper end because the remelting cycle and the long solution and ageing treatments both add days.
Jiangyin Jiangnan Metal Co., Ltd. is an integrated melting works and open-die forging factory in Zhouzhuang Town, Jiangyin City, Jiangsu Province, operating since 1997. The plant employs 460 people, including 9 senior engineers, 32 intermediate engineers and 140 technicians, and holds CCS, BV, DNV, LR and NK approvals. We forge carbon steel, alloy steel, tool steel, stainless steel and nickel-base superalloys into rings, discs, shafts, sleeves, blocks and near-net-shape parts, working to customer drawings and international specifications.
For Alloy 783 we control the process from the furnace through forging, heat treatment, non-destructive testing and machining, and issue a mill certificate traceable to the melt number on every piece.
Technical data reviewed by the engineering team at Jiangyin Jiangnan Metal Co., Ltd. · Last updated