Nickel superalloy / open-die forgings
Alloy X-750 Forgings (UNS N07750): Forged Rings, Discs, Shafts and Bars
Alloy X-750 (UNS N07750, W.Nr. 2.4669, GB GH4145, also sold under the trade name Inconel® X-750) is a precipitation-hardenable nickel-chromium superalloy. Aluminium and titanium additions form a γ′ Ni3(Ti, Al) phase during ageing, which is what gives the alloy its tensile and creep-rupture strength up to 704 °C (1300 °F). Above that the hardening effect falls away, but heat-treated material still carries useful load to around 982 °C (1800 °F), and the alloy also works at cryogenic temperatures. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We forge Alloy X-750 rings, seamless rolled rings, discs, shafts, flanges, sleeves, bushings, tube sheets and round bars to ASTM B637 / ASME SB-637 and AMS 5667-5671, with EN 10204 3.1 or 3.2 certification.
- Common names
- Alloy X-750, X750, Inconel X-750
- UNS number
- N07750
- Werkstoff / DIN
- 2.4669, NiCr15Fe7TiAl
- China GB grade
- GH4145 (formerly GH145)
- Alloy family
- Precipitation-hardenable Ni-Cr superalloy
- Density
- 8.28 g/cm³ (0.299 lb/in³)
- High-strength service to
- 704 °C / 1300 °F
- Oxidation resistance to
- about 982 °C / 1800 °F
- Forging standard
- ASTM B637, ASME SB-637
- Melting route
- EAF + VOD + ESR
- Forms produced
- Rings, discs, shafts, bars, flanges, sleeves
- Manufacturer
- Jiangyin Jiangnan Metal Co., Ltd. (China)
Values on this page are typical for the alloy. Unless a figure is marked as a specification limit, do not use it as an acceptance value. Order limits are confirmed on the mill test certificate.
What Alloy X-750 is, and why it is forged
Alloy X-750 came out of Alloy 600. Adding aluminium and titanium made the nickel-chromium matrix precipitation hardenable, and the γ′ phase that forms during ageing is what gives the alloy its relaxation resistance, its creep-rupture strength, and its resistance to chloride stress-corrosion cracking in the fully aged condition.
The alloy work-hardens fast and grain size has to be kept under control, so heavy sections are normally open-die forged. Forging closes ingot porosity, refines the grain, and puts the flow lines around the part instead of cutting through them, which is what you lose when a component is machined out of solid bar.
- Strength with heat. High tensile and creep-rupture strength to 704 °C (1300 °F), useful strength to about 982 °C (1800 °F).
- Relaxation resistance. The reason X-750 is the usual choice for high-temperature springs, bolting and fasteners.
- Cryogenic toughness. Properties hold up at sub-zero and cryogenic service temperatures.
- Corrosion and oxidation. Resistant under oxidising and reducing industrial conditions, with good chloride SCC resistance when fully age hardened.
- Weldability. Limited by strain-age cracking under heavy restraint. Procedures and post-weld heat treatment have to be qualified.
Equivalent designations and specifications for Alloy X-750
| System | Designation |
|---|---|
| UNS (USA) | N07750 |
| Werkstoff / DIN (Germany) | 2.4669, NiCr15Fe7TiAl |
| GB (China) | GH4145 / GH145 |
| JIS (Japan) | NCF 750 |
| BS (UK) | HR 505, NA 75 |
| AFNOR (France) | NC15FeT |
| ASTM / ASME, bars and forgings | ASTM B637, ASME SB-637 |
| SAE AMS, bars, forgings, rings | AMS 5667, 5668, 5669, 5670, 5671, 5747 |
| SAE AMS, sheet, strip, plate, wire | AMS 5542, 5582, 5598, 5698, 5699 |
| Sour service | NACE MR0175 / ISO 15156-3 on request |
Chemical composition of Alloy X-750 (ASTM B637 UNS N07750)
| Element | Minimum, % | Maximum, % |
|---|---|---|
| Nickel + Cobalt (Ni + Co) | 70.00 | balance |
| Chromium (Cr) | 14.00 | 17.00 |
| Iron (Fe) | 5.00 | 9.00 |
| Titanium (Ti) | 2.25 | 2.75 |
| Niobium + Tantalum (Nb + Ta) | 0.70 | 1.20 |
| Aluminium (Al) | 0.40 | 1.00 |
| Cobalt (Co) | - | 1.00 |
| Manganese (Mn) | - | 1.00 |
| Silicon (Si) | - | 0.50 |
| Copper (Cu) | - | 0.50 |
| Carbon (C) | - | 0.08 |
| Sulfur (S) | - | 0.010 |
Where a customer specification is tighter than ASTM B637, for example restricted Mn or Co for nuclear or aerospace work, the aim analysis is agreed before melting.
Heat treatment of Alloy X-750 forgings: Types 1, 2 and 3
ASTM B637 splits UNS N07750 bars and forgings into three heat-treatment types. Which one you order has more effect on the delivered properties than anything else on the specification, so state it on the purchase order. We run solution treatment, stabilising and ageing in house on calibrated furnaces and keep the charts.
| Type | Intended service | Cycle |
|---|---|---|
| Type 1, triple treatment | Above 593 °C (1100 °F), long sustained loads | Solution 1149 ± 14 °C (2100 ± 25 °F), 2-4 h, AC. Stabilise 843 ± 14 °C (1550 ± 25 °F), 24 h, AC. Age 704 ± 14 °C (1300 ± 25 °F), 20 h, AC or FC |
| Type 2, solution + furnace-cool age | Up to 593 °C (1100 °F) | Solution 982 ± 14 °C (1800 ± 25 °F), 0.5 h min, AC or faster. Age 732 ± 14 °C (1350 ± 25 °F), 8 h, FC to 621 ± 14 °C (1150 ± 25 °F), hold to 18 h total, AC |
| Type 3, solution + age | General purpose, highest strength band | Solution 1079-1121 °C (1975-2050 °F), 1-2 h, AC. Age 704 ± 14 °C (1300 ± 25 °F), 20-24 h, AC |
Mechanical properties of Alloy X-750
Specified minimum room-temperature properties by heat-treatment type
| Condition | Tensile strength, min. | Yield strength 0.2 %, min. | Elongation, min. | Reduction of area, min. | Hardness, HB |
|---|---|---|---|---|---|
| Type 1 | 965 MPa (140 ksi) | 620 MPa (90 ksi) | 8 % | - | 262 min |
| Type 2a, dia. under 63.5 mm | 1170 MPa (170 ksi) | 790 MPa (115 ksi) | 18 % | 18 % | 302-363 |
| Type 2b, dia. 63.5-101.6 mm | 1170 MPa (170 ksi) | 790 MPa (115 ksi) | 15 % | 15 % | 302-363 |
| Type 3 | 1103-1276 MPa (160-185 ksi) | 689-896 MPa (100-130 ksi) | 20 % | 20 % | 267-363 |
Stress-rupture check for Type 1 material supplied solution treated plus aged: 732 °C (1350 °F) under 310 MPa (45 ksi) must survive at least 100 h with 5 % minimum elongation.
Typical short-time tensile properties at elevated temperature
| Test temp. °C | Test temp. °F | Yield 0.2 %, MPa | Yield 0.2 %, ksi | Tensile, MPa | Tensile, ksi | Elong. in 50.8 mm, % | R. of area, % |
|---|---|---|---|---|---|---|---|
| 21 | 70 | 634 | 92 | 1110 | 161 | 22 | 30 |
| 538 | 1000 | 572 | 83 | 965 | 140 | 20 | 30 |
| 649 | 1200 | 565 | 82 | 827 | 120 | 10 | 21 |
| 760 | 1400 | 469 | 68 | 552 | 80 | 10 | 22 |
| 816 | 1500 | 310 | 45 | 324 | 47 | 20 | 32 |
Physical properties of Alloy X-750
| Property | Value |
|---|---|
| Density | 8.28 g/cm³ (0.299 lb/in³) |
| Melting range | 1393-1427 °C (2540-2600 °F) |
| Strengthening mechanism | γ′ Ni3(Ti, Al) precipitation |
| Magnetic response | Essentially non-magnetic at room temperature when aged |
| Hot working temperature | About 1040 °C (1900 °F) and above |
| Cold forming | Possible in the annealed condition, work-hardens fast |
Alloy X-750 forged forms and size range
We forge Alloy X-750 to customer drawing or to a rough-machined envelope. The sizes below cover the working range of our open-die presses and ring-rolling mill. Anything near the top of a range is checked against the drawing before we quote.
| Forged form | Typical size range | Notes |
|---|---|---|
| Seamless rolled rings | OD 200-3000 mm, height to 800 mm | Radial-axial rolled, grain flow follows the circumference |
| Forged rings, retaining rings | OD 100-2000 mm | Upset and punched, or mandrel forged |
| Discs and blanks | Dia. 100-1800 mm, thk. 20-500 mm | Turbine wheels, blind flanges, valve discs |
| Shafts and spindles | Dia. 50-800 mm, length to 6000 mm | Stepped and eccentric shafts to drawing |
| Round bars | Dia. 20-600 mm | Forged, peeled, turned or ground |
| Flanges | DN 15 to DN 1200, ASME B16.5 / B16.47 or drawing | WN, SO, BL, LJ and special profiles |
| Sleeves, bushings, hollow bars | OD to 1200 mm, bored ID from 60 mm | Trepanned, or punched and expanded |
| Tube sheets and plates | Dia. to 2500 mm, thk. to 400 mm | Heat exchanger and pressure vessel service |
| Valve stems, seats, bodies, blocks | To drawing | Ball, gate, globe, check and plug valves |
| Single piece weight | 5 kg to 20 000 kg | Heavier pieces on enquiry |
Supply condition: as forged, rough turned, solution treated, solution treated and aged, or fully machined to finished dimensions.
How Jiangyin Jiangnan Metal forges Alloy X-750
- Melting. EAF and VOD, then ESR remelting. This keeps sulfur and gas content low and gives a clean ingot with little segregation, which matters on a Ti and Al bearing alloy.
- Forging. Hydraulic open-die press work with controlled soak time, reduction ratio and finish temperature, to break down the as-cast structure and refine grain size.
- Ring rolling. Radial-axial mill for seamless rolled rings, so the grain flow follows the ring circumference.
- Heat treatment. Solution, stabilising and ageing cycles to ASTM B637 Type 1, 2 or 3, with furnace charts retained.
- Machining. Rough turning, boring, trepanning, or fully finished machining to the customer drawing.
Testing, inspection and certification
- Chemical analysis. Ladle analysis, and product analysis on request.
- Mechanical testing. Room-temperature and elevated-temperature tensile, hardness, impact and stress-rupture testing as specified.
- Ultrasonic testing. To EN 10228-3, SEP 1921, ASTM A388, or the customer acceptance class.
- Surface NDT. Liquid penetrant to ASTM E165, or magnetic particle where the geometry allows.
- Metallography. Grain size and microstructure examination on request.
- Documentation. EN 10204 3.1 certificate as standard. EN 10204 3.2 with third-party witness on request.
- Marking and traceability. Heat number, grade, drawing and item number hard stamped or vibro etched.
Where Alloy X-750 forgings are used
| Industry | Typical forged components |
|---|---|
| Gas turbines and aero engines | Rotor blades and wheels, seal rings, bolts, structural members, thrust reverser parts |
| Nuclear power | Reactor internals, hold-down springs, fasteners, guide tube components |
| Oil, gas and subsea | Wellhead and Christmas tree parts, subsea connectors, sleeves, bushings, discs |
| Valves and flow control | Valve stems, seat rings, bodies, blocks and discs for ball, gate, globe, check and plug valves |
| Pressure vessels and heat exchangers | Tube sheets, forged flanges, nozzles, shell rings for shell and tube exchangers and air receivers |
| Rotating equipment | Shafts, spindles, gears, couplings for compressors, gearboxes and power transmission |
| Chemical and process plant | Pump shafts, columns, towers, reactor internals, preheater parts |
| Tooling and heat treatment | Extrusion dies, forming tools, heat-treating fixtures, test machine grips |
| Springs and fasteners | High-temperature springs and bolting, from cryogenic service up to 649 °C (1200 °F) |
Frequently asked questions about Alloy X-750 forgings
Is Alloy X-750 the same as Inconel X-750?
Yes. Alloy X-750, X750 and Inconel® X-750 all refer to UNS N07750 / W.Nr. 2.4669. INCONEL is a registered trademark of Special Metals Corporation, so independent producers such as Jiangyin Jiangnan Metal Co., Ltd. supply the material as Alloy X-750 or UNS N07750, to the same ASTM B637 chemistry and property limits.
What is the maximum service temperature of Alloy X-750?
Alloy X-750 holds high strength up to about 704 °C (1300 °F). Above that, the precipitation hardening is progressively lost, but heat-treated material still has useful strength to roughly 982 °C (1800 °F), and reasonable oxidation resistance in combustion gas to about 870 °C (1600 °F). For sustained loads above 593 °C (1100 °F), specify the Type 1 triple heat treatment.
Which standard applies to Alloy X-750 forgings?
ASTM B637, and the identical ASME SB-637, is the main standard for precipitation-hardening nickel alloy bars, forgings and forging stock for high-temperature service. Aerospace work is normally ordered to AMS 5667, 5668, 5670 or 5671, depending on the heat-treatment route required.
What is the difference between Alloy X-750 and Inconel 718?
Inconel 718 is niobium rich and hardens through γ″ Ni3Nb, which gives it higher strength up to about 650-700 °C and much better weldability. Alloy X-750 hardens through γ′ Ni3(Ti, Al) and is the usual choice where relaxation resistance in springs and bolting matters, or where service temperature is above the 718 range and weld fabrication is not the main concern.
Can Alloy X-750 be welded?
It can, but weldability is limited by strain-age cracking under heavy restraint, because of the aluminium and titanium content. Weld in the solution-annealed condition where possible, control heat input and restraint, and qualify the post-weld heat treatment. For heavily restrained joints, discuss the design before ordering.
Who supplies Alloy X-750 forged rings and discs in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It produces Alloy X-750 (UNS N07750) seamless rolled rings, forged rings, discs, shafts, flanges, sleeves, bushings, tube sheets and round bars to ASTM B637. Enquiries: +86 189 2135 9659 or sales@steelforgepieces.com.
What do you need to quote an Alloy X-750 forging?
The drawing or the finished dimensions, the quantity, the standard and heat-treatment type (ASTM B637 Type 1, 2 or 3), the supply condition (as forged, rough machined or finish machined), the NDT acceptance class, and the certificate level (EN 10204 3.1 or 3.2). With that we can normally give a firm price and lead time within one working day.
What is the minimum order quantity for Alloy X-750 forgings?
Open-die forgings are made to order, so single pieces are accepted. X-750 is melted in heats and we do not hold every section in stock, so a small quantity in an unusual size can carry a minimum melt or billet charge. Where that applies, it is shown in the quotation.
How is Alloy X-750 tested before shipment?
The standard scope is chemical analysis, room-temperature tensile and hardness testing, and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Elevated-temperature tensile, stress rupture, impact, grain size and penetrant testing are added when the specification calls for them. Results are issued on an EN 10204 3.1 certificate, or 3.2 with third-party witness.
Request a quotation for Alloy X-750 forgings
Send the drawing or the dimensions and we will quote the forging, the heat treatment and the test scope as one price. Quotations normally go out within one working day.
Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging FactoryNo. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone / WhatsApp / WeChat: +86 189 2135 9659
Email: sales@steelforgepieces.com
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Technical sales, Jiangyin Jiangnan Metal Co., Ltd. Published . Last reviewed .