Inconel 751 Forgings (UNS N07751)
Alloy 751 · W.-Nr. 2.4694 · Precipitation-hardenable nickel–chromium superalloy
Reviewed and updated · Published by Jiangyin Jiangnan Metal Co., Ltd.
- Common designation
- Inconel 751 / Alloy 751
- UNS number
- N07751
- Werkstoff number
- 2.4694
- Alloy system
- Ni–Cr, age-hardenable
- Forging temperature
- 980–1205 °C (1800–2200 °F)
- Strengthening phase
- γ′ Ni3(Al,Ti)
- Typical specifications
- ASTM B637, ASTM B564
- Certification
- EN 10204 3.1 / 3.2
Inconel 751 (UNS N07751, Werkstoff 2.4694) is a precipitation-hardenable nickel–chromium superalloy, developed as a higher-aluminum modification of Inconel X-750 and used mainly for the exhaust valves of internal combustion engines. The extra aluminum raises stress-rupture strength around 870 °C (1600 °F). In most other respects the alloy behaves like X-750, and X-750 data is widely used for 751 design work. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We forge Inconel 751 into seamless rolled rings, discs, shafts, round bars, flanges, sleeves, bushings and tube sheets to customer drawing.
Key facts
- Identification: Inconel 751 = UNS N07751 = Werkstoff 2.4694 = Alloy 751.
- Composition: nickel 70 % minimum, chromium 14–17 %, iron 5–9 %, titanium 2.00–2.60 %, aluminum 0.90–1.50 %, niobium 0.70–1.20 %.
- Room-temperature strength, aged: 1275 MPa tensile, 875 MPa yield at 0.2 % offset, 25 % elongation.
- Forging range: 980–1205 °C. Reheat to 1205 °C whenever the workpiece falls below 980 °C.
- Difference from X-750: aluminum is roughly doubled, 0.90–1.50 % against 0.40–1.00 %, which improves rupture strength near 870 °C.
- Main application: exhaust valves for heavy-duty diesel and gas engines. Also turbocharger parts, gas-turbine hardware and high-temperature fasteners.
- Supplied by: Jiangyin Jiangnan Metal Co., Ltd., No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin, Jiangsu, China. Open-die forgings from EAF + VOD + ESR melted stock, ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388.
Chemical composition of Inconel 751
The chemical composition of Inconel 751 (UNS N07751) is nickel 70 % minimum, chromium 14.0–17.0 %, iron 5.0–9.0 %, titanium 2.00–2.60 %, aluminum 0.90–1.50 % and niobium 0.70–1.20 %, with carbon held to 0.10 % maximum and sulfur to 0.010 % maximum. Aluminum and titanium are the deliberate additions. Together with nickel they precipitate the γ′ phase Ni3(Al,Ti), which is what gives the alloy its strength after aging.
| Element | Symbol | Content (%) | Role |
|---|---|---|---|
| Nickel | Ni | ≥ 70.0 | Base; forms γ′ with Al and Ti |
| Chromium | Cr | 14.0–17.0 | Oxidation and hot-corrosion resistance |
| Iron | Fe | 5.0–9.0 | Balance element |
| Titanium | Ti | 2.00–2.60 | γ′ former |
| Aluminum | Al | 0.90–1.50 | γ′ former, raised against X-750 |
| Niobium | Nb (Cb) | 0.70–1.20 | Precipitation strengthening |
| Manganese | Mn | ≤ 1.00 | Residual |
| Copper | Cu | ≤ 0.50 | Residual |
| Silicon | Si | ≤ 0.50 | Residual |
| Carbon | C | ≤ 0.10 | Carbide former, kept low |
| Sulfur | S | ≤ 0.010 | Impurity, restricted for hot workability |
Ranges follow the published limits for UNS N07751. Our Inconel 751 stock is melted by EAF + VOD and then ESR remelted. The actual heat analysis appears on every EN 10204 3.1 or 3.2 certificate we issue.
Mechanical properties of Inconel 751
In the precipitation-hardened condition at room temperature, Inconel 751 has a tensile strength of 1275 MPa (184,900 psi), a 0.2 % offset yield strength of 875 MPa (127,000 psi) and elongation at break of 25 %. Strength falls as temperature rises, but the higher aluminum content keeps stress-rupture life useful to about 870 °C (1600 °F). That is the operating range of an engine exhaust valve, and it is the reason the grade exists.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 1275 MPa | 184,900 psi |
| Yield strength (0.2 % offset) | 875 MPa | 127,000 psi |
| Elongation at break | 25 % | 25 % |
| Modulus of elasticity, 20 °C | 214 GPa | 31.0 × 106 psi |
| Modulus of elasticity, 538 °C | 184 GPa | 26.7 × 106 psi |
These are typical values for aged material, not acceptance criteria. Section size, forging reduction and the exact aging cycle all move the numbers. Modulus figures follow published X-750 data, whose elastic and thermal behaviour Inconel 751 closely matches. Tell us the minimums your drawing requires and we will confirm them against the actual heat before production starts.
Physical properties of Inconel 751
Inconel 751 shares its thermal and physical behaviour with Inconel X-750, and published X-750 data is used industry-wide for 751 design work. Typical values:
| Property | Value |
|---|---|
| Density | 8.28 g/cm³ (0.299 lb/in³) |
| Thermal conductivity | 12.0 W/m·K |
| Coefficient of thermal expansion, 20–538 °C | 14.5 µm/m·°C |
| Electrical resistivity | 122 µΩ·cm |
| Modulus of rigidity, 20 °C | 82.7 GPa |
Inconel 751 compared with Inconel X-750
The difference between Inconel 751 and Inconel X-750 is aluminum content. Inconel 751 carries 0.90–1.50 % aluminum against 0.40–1.00 % in X-750, with slightly less titanium. Nickel, chromium, iron and niobium are nominally the same in both. The extra aluminum produces more γ′ and better stress-rupture strength near 870 °C (1600 °F). Do not substitute one grade for the other on a drawing. Order against the UNS number rather than the trade name.
| Attribute | Inconel 751 | Inconel X-750 |
|---|---|---|
| UNS number | N07751 | N07750 |
| Werkstoff number | 2.4694 | 2.4669 |
| Aluminum | 0.90–1.50 % | 0.40–1.00 % |
| Titanium | 2.00–2.60 % | 2.25–2.75 % |
| Nickel | ≥ 70 % | ≥ 70 % |
| Chromium | 14.0–17.0 % | 14.0–17.0 % |
| Iron | 5.0–9.0 % | 5.0–9.0 % |
| Strength advantage | Higher stress-rupture strength near 870 °C | Baseline |
| Typical use | Engine exhaust valves, turbocharger parts | Springs, fasteners, aerospace and nuclear components |
Heat treatment of Inconel 751 forgings
Inconel 751 forgings are strengthened by solution treatment followed by a two-stage age. The cycle used for valve service is: solution treat at about 1150 °C, air cool; age at 843 °C for 24 hours, air cool; then age at 704 °C for 20 hours, air cool. A small permanent contraction of roughly 0.0003 in/in happens during precipitation, so close-tolerance features should be machined after aging.
| Stage | Temperature | Time | Cooling |
|---|---|---|---|
| Solution treatment | 1150 °C (2100 °F) | 2–4 h | Air cool |
| Anneal (alternative) | 1177 °C (2150 °F) | 1 h | Air cool |
| First age | 843 °C (1550 °F) | 24 h | Air cool |
| Second age | 704 °C (1300 °F) | 20 h | Air cool |
The cycles above are typical. Where a purchase order names a specification or a customer heat-treat procedure, we run that procedure and keep the furnace chart. Forgings can be solution treated and aged before shipment, or supplied solution treated only for aging after machining. Please state which you need on the enquiry.
Forging and fabrication of Inconel 751
The hot working range for Inconel 751 is 980–1205 °C (1800–2200 °F). Once the workpiece drops below 980 °C it goes back into the furnace and comes up to 1205 °C before forging continues. Working the alloy below its range risks cracking and leaves a coarse, uneven grain structure.
Open-die forging route
- Incoming stock. ESR-remelted Inconel 751 ingot or billet, checked against its mill certificate and chemical analysis on arrival.
- Heating. Soak to 1205 °C. Soak time is set by section thickness, not by the clock alone.
- Cogging and upsetting. Break down the cast structure and work the material to the required forging reduction ratio.
- Ring rolling or drawing out. Seamless rolled rings are expanded on the ring mill. Shafts and bars are drawn out under the press.
- Reheat as needed. Back to the furnace whenever surface temperature approaches 980 °C.
- Heat treatment. Solution treat and age per the cycle above or per the customer specification.
- Rough machining. Machined slightly oversize. Final size is taken after aging to allow for precipitation contraction.
- Inspection and certification. Dimensional check, ultrasonic testing, mechanical test, EN 10204 3.1 or 3.2 certificate.
Machining and welding
Inconel 751 machines like other age-hardenable nickel alloys: rigid setup, positive rake, low surface speed, plenty of coolant. The practical sequence is to machine slightly oversize in the as-forged condition, precipitation heat treat, then finish to size. The alloy welds by shielded metal-arc, gas-tungsten arc, gas metal-arc and submerged-arc processes, and weldments intended for service at temperature are normally re-aged afterwards. Hot hardness is good enough that valve seat faces usually need no hardfacing.
Forms, sizes and forging capability
We produce Inconel 751 as open-die forgings, made to customer drawing or to a dimensioned enquiry. Common forms:
| Form | Typical size range | Notes |
|---|---|---|
| Seamless rolled rings | OD 200–3000 mm | Ring-rolled, radial and axial reduction recorded |
| Forged discs and blanks | Ø 100–2000 mm | Upset forged, grain flow across the face |
| Round bars | Ø 20–600 mm | Drawn out, rough turned or peeled |
| Shafts and spindles | Length up to 6000 mm | Stepped shafts to drawing |
| Flanges | To drawing | Weld neck, blind, slip-on, special profiles |
| Sleeves and bushings | To drawing | Bored and faced |
| Tube sheets | To drawing | Forged and rough machined |
| Valve components | To drawing | Stems, seats, bodies, blocks |
Send a drawing, or the outside diameter, inside diameter, height and quantity, and we will confirm feasibility and price. Open-die work has no fixed catalogue, so unusual geometry is normal here.
Testing and certification
Every Inconel 751 forging leaves the works with documentation. Standard scope:
- Chemical analysis. Heat analysis reported against the UNS N07751 limits.
- Mechanical testing. Tensile, yield and elongation on test coupons representing the forging.
- Ultrasonic testing. To EN 10228-3, SEP 1921 or ASTM A388, whichever the order calls for. The acceptance class is stated on the certificate.
- Dimensional inspection. Against the approved drawing.
- Certification. EN 10204 3.1 issued by the works, or EN 10204 3.2 countersigned by a third-party inspection body such as SGS, BV, TUV or Lloyd's Register.
- On request. PMI, hardness survey, grain size, impact testing, dye penetrant and magnetic particle inspection where applicable.
Applications of Inconel 751 forgings
Inconel 751 gets specified where a part has to hold its strength and resist oxidation in hot exhaust gas or combustion products. The dominant application is the exhaust valve of a heavy-duty internal combustion engine. Forged 751 parts also turn up in:
- Engines and turbochargers. Exhaust valves for diesel and gas engines in trucks, locomotives, marine plant, tractors, drilling rigs and mobile generating sets, plus turbocharger rotors and other hot-side hardware.
- Gas turbines and power generation. Rings, discs and fasteners in hot-section assemblies running above the useful range of stainless steel.
- Process and pressure equipment. Forged flanges, tube sheets, nozzles and shafts for heat exchangers, pressure vessels and reactor internals.
- Valves and wellhead equipment. Valve stems, seat rings, bodies and blocks for high-temperature service.
- Rotating equipment. Shafts, spindles, sleeves and bushings in pumps, compressors and gearboxes exposed to heat.
If your drawing calls for a different nickel grade, we forge the full range. See the related grades below.
Frequently asked questions about Inconel 751
What is Inconel 751?
Inconel 751 is a precipitation-hardenable nickel–chromium superalloy, designated UNS N07751 and Werkstoff 2.4694. It is a modified version of Inconel X-750 with a higher aluminum content, used mainly for the exhaust valves of internal combustion engines. Strength comes from aging, which precipitates the γ′ phase Ni3(Al,Ti).
What is the UNS number for Inconel 751?
The UNS number for Inconel 751 is N07751. The equivalent German material number is Werkstoff 2.4694. The alloy is also called Alloy 751.
What is the difference between Inconel 751 and Inconel X-750?
Aluminum content. Inconel 751 contains 0.90–1.50 % aluminum against 0.40–1.00 % in Inconel X-750, with slightly lower titanium. Nickel, chromium, iron and niobium are nominally identical. The higher aluminum gives Inconel 751 better stress-rupture strength around 870 °C (1600 °F), which is why it became the exhaust-valve grade. The two are not interchangeable, so order against the UNS number: N07751 for 751, N07750 for X-750.
What is Inconel 751 used for?
Mostly the exhaust valves of heavy-duty diesel and gas engines used in trucks, locomotives, ships, tractors, drilling rigs and mobile power plant. It also goes into turbocharger components, gas-turbine hot-section hardware, high-temperature fasteners, and forged valve and process parts that run hot.
What is the forging temperature range for Inconel 751?
980–1205 °C (1800–2200 °F). Reheat the workpiece to 1205 °C whenever its temperature falls below 980 °C. Forging outside this range risks cracking and produces uneven grain structure.
What heat treatment does Inconel 751 need?
A solution treatment followed by a two-stage age. The typical valve-service cycle is: solution treat at about 1150 °C and air cool; age at 843 °C for 24 hours and air cool; age at 704 °C for 20 hours and air cool. Expect a permanent contraction of roughly 0.0003 in/in during precipitation, so finish-machine after aging.
Which standards cover Inconel 751 forgings?
Bar and forging material is commonly ordered to ASTM B637, which covers precipitation-hardening nickel alloy bars, forgings and forging stock, and to ASTM B564 for nickel alloy forgings. Certification follows EN 10204 3.1 or 3.2. Ultrasonic acceptance is normally written to EN 10228-3, SEP 1921 or ASTM A388. Confirm the exact specification and revision on your enquiry, because acceptance criteria differ between them.
Can Inconel 751 be welded and machined?
Yes to both. Inconel 751 welds by shielded metal-arc, gas-tungsten arc, gas metal-arc and submerged-arc processes, and weldments for hot service are normally re-aged. Machining uses conventional methods for age-hardenable nickel alloys: rigid setup, positive rake, low surface speed, plenty of coolant. Machine oversize first, age, then finish to size.
What Inconel 751 forms and sizes does Jiangyin Jiangnan Metal supply?
Jiangyin Jiangnan Metal Co., Ltd. supplies Inconel 751 as open-die forgings: seamless rolled rings, discs and blanks, round bars, shafts and spindles, flanges, sleeves, bushings, tube sheets and forged valve components. Everything is made to drawing, so send the drawing or the key dimensions and quantity and we will confirm feasibility.
How do I get a quotation for Inconel 751 forgings?
Email sales@steelforgepieces.com or call +86 189 2135 9659 with the drawing or dimensions, quantity, the specification you are ordering to, the delivery condition (as-forged, solution treated, or solution treated and aged) and the certificate type you need. A quotation normally follows within one working day.
Request a quotation for Inconel 751 forgings
Send a drawing or the basic dimensions and we will price it. Open-die forging means non-standard geometry is ordinary work here.
- Company
- Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
- Address
- No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone
- +86 189 2135 9659
- sales@steelforgepieces.com
- Website
- www.steelforgepieces.com
Related nickel alloy grades we forge
- Inconel X-750
- Inconel 718
- Inconel 706
- Inconel 625
- Inconel 600
- Inconel 601
- Inconel 617
- Nimonic 80A
- Nimonic 90
- Waspaloy
- Udimet 720
- Monel K-500
About the supplier
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The works produces forged rings, discs, shafts, bars, flanges, sleeves and tube sheets in carbon steel, alloy steel, tool steel, stainless steel and nickel-based superalloys including Inconel 751 (UNS N07751). Forgings are supplied against customer drawings with EN 10204 3.1 or 3.2 certification and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388.