Inconel X750 (UNS N07750) is a precipitation-hardenable nickel-chromium superalloy with exceptional strength at temperatures up to 700°C (1,290°F). It is used in aerospace turbines, nuclear reactors, rocket engines, and high-temperature springs.
- Chemical base: Ni+Co ≥70%, Cr 14–17%, Fe 5–9%, Ti 2.25–2.75%
- Tensile strength: ~1,200 MPa at room temperature (STA condition)
- Three ASTM B637 heat treatment types: Type 1 (AMS 5668), Type 2 (AMS 5667), Type 3 (AMS 5598)
- Also retains properties at cryogenic temperatures (down to −250°C)
- Available as closed die, open die, and seamless ring forgings per ASTM B637
What Is Inconel X750? — Overview
Definition: Inconel X750 is a precipitation-hardenable nickel-chromium superalloy (UNS N07750) engineered for exceptional mechanical strength, oxidation resistance, and corrosion resistance at temperatures up to 700°C (1290°F), with additional capability at cryogenic temperatures.
When conventional steels buckle under sustained heat, and stainless grades corrode in aggressive chemical environments, engineers reach for a small, specialized family of materials known as nickel superalloys. Among them, Inconel X750 (UNS N07750) holds a distinguished position.
It is a precipitation-hardenable nickel-chromium alloy engineered to deliver extraordinary mechanical strength under sustained high temperatures while resisting oxidation and corrosive attack. First developed in the 1940s to serve the demands of early jet propulsion technology, Inconel X750 has since found application in gas turbines, rocket engine thrust chambers, nuclear reactor core internals, high-temperature springs, and critical fasteners deployed globally.
Inconel X750 is not merely a high-temperature material — it is a precision instrument of metallurgical engineering, where every alloying element plays a deliberate, quantified role in extending the performance envelope.
Its combination of mechanical performance and manufacturability — it can be forged, machined, welded (with precautions), and age-hardened — makes X750 one of the most versatile superalloys in modern engineering. This guide covers chemistry, properties, heat treatment types, forging methods, applications, comparison with Inconel 718, and supplier selection criteria. If you are sourcing Inconel X750 forged parts, visit our product page for custom quotation and full technical specifications.
"Inconel" is a registered trademark of Special Metals Corporation (now part of Precision Castparts Corp.) used to describe a family of nickel-chromium-based superalloys. The generic designation for Inconel X750 is Nickel Alloy UNS N07750 or W.Nr 2.4669. Not all manufacturers use the Inconel trademark; suppliers may refer to the material by its UNS or AMS designation.
Chemical Composition — Every Element Has a Purpose
Key fact: Inconel X750 is hardened by additions of aluminum (0.40–1.00%) and titanium (2.25–2.75%), which together form the gamma prime (γ') precipitate phase Ni₃(Al,Ti) — the primary strengthening mechanism that gives the alloy its high-temperature capability.
Inconel X750 is a nickel-chromium base superalloy whose strength arises from controlled additions of aluminum and titanium. During heat treatment, these elements precipitate out of the nickel matrix to form coherent Ni₃(Al,Ti) particles — the γ' phase — which impede dislocation movement and sustain strength at elevated temperatures.
| Element | Min % | Max % | Primary Metallurgical Role |
|---|---|---|---|
| Nickel + Cobalt | 70.00 | — | Austenitic FCC matrix; base for γ' formation; high-temp phase stability |
| Chromium (Cr) | 14.0 | 17.0 | Forms Cr₂O₃ protective oxide film; oxidation & corrosion resistance |
| Iron (Fe) | 5.0 | 9.0 | Microstructure balance; cost moderator in nickel base |
| Titanium (Ti) | 2.25 | 2.75 | Primary γ' precipitate former with Al; key strengthening agent |
| Columbium + Tantalum (Nb+Ta) | 0.70 | 1.20 | Carbide former; grain boundary strengthening; prevents grain growth |
| Aluminum (Al) | 0.40 | 1.00 | Co-forms γ' precipitate Ni₃(Al,Ti); enhances oxidation barrier |
| Manganese (Mn) | — | 1.00 | Deoxidizer during vacuum induction melting |
| Silicon (Si) | — | 0.50 | Deoxidizer; minor oxidation resistance contribution |
| Copper (Cu) | — | 0.50 | Controlled as impurity; minimal effect below maximum |
| Carbon (C) | — | 0.08 | Carbide formation at grain boundaries; low levels are beneficial |
| Cobalt (Co) | — | 1.00 | Solid-solution strengthener; included within Ni+Co minimum |
| Sulfur (S) | — | 0.01 | Tightly controlled — prevents hot shortness during forging |
A closely related variant, UNS N07752, is available as billet for forging with stricter limits on Carbon (≤0.05%) and Cobalt (≤0.05%). It is specified when cleaner grain boundaries and tighter compositional control are required for critical aerospace or nuclear applications where improved notch rupture ductility is a design driver.
Mechanical & Physical Properties
Key fact: In the STA (solution-treated and aged) condition, Inconel X750 has a typical UTS of ~1,200 MPa, yield strength of ~815 MPa, elongation of ~27%, and hardness of HRC 32–42. Properties decrease with increasing temperature but remain significant up to 700°C.
| Physical Property | Value | Notes / Condition |
|---|---|---|
| Melting Range | 1,393 – 1,427°C (2,540 – 2,600°F) | Solidus to liquidus |
| Modulus of Elasticity | 214 GPa (31 MSI) | STA condition at room temp |
| Thermal Conductivity | 11.5 W/m·K | At 20°C |
| Thermal Expansion Coefficient | 12.6 × 10⁻⁶ /°C | RT to 427°C (RT–800°F) |
| Electrical Resistivity | 1.22 μΩ·m | Room temperature |
| Machinability Rating | 16 | Relative to free-machining steel = 100 |
| Magnetic Permeability | ~1.001 (non-magnetic) | Solution-annealed condition |
Unlike most high-temperature alloys, Inconel X750 retains excellent mechanical properties at both extremes of temperature. It performs reliably at cryogenic temperatures down to approximately −250°C (−418°F) AND at sustained service temperatures up to 700°C (1,290°F) — making it uniquely suited for rocket engine components that endure cryogenic propellant contact and combustion chamber heat in the same component.
Heat Treatment — The Three ASTM B637 Types
Key fact: The mechanical properties of Inconel X750 are not inherent — they must be built in through heat treatment. ASTM B637 defines three types: Type 1 (triple treatment, AMS 5668) for high-temp creep service; Type 2 (equalization + precipitation, AMS 5667) for maximum room-temperature strength; Type 3 (AMS 5598) for springs and bolts.
Inconel X750's strength properties are entirely dependent on the precipitation heat treatment applied after forging. ASTM B637 defines three heat treatment types, each optimizing the alloy for a specific service temperature range. Specifying the wrong type in your purchase order is the most common cause of field failures with this alloy.
Step 2: Stabilize at 843°C (1,550°F) for 24 hours, air cool.
Step 3: Precipitation harden at 704°C (1,300°F) for 20 hours, air or furnace cool.
Purpose: Produces optimal creep-rupture strength and microstructural stability at the highest service temperatures.
Step 2: Precipitation harden at 732°C (1,350°F) for 8 hours, furnace cool to 621°C, hold total precipitation time 18 hours, air cool.
Sub-types: 2a for diameter <63.5 mm; 2b for 63.5–101.6 mm. Provides highest room-temperature tensile properties.
Step 2: Precipitation harden at 704°C (1,300°F) for 20–24 hours, air cool.
Balances high tensile strength with excellent relaxation resistance. Most commonly specified for springs and high-temperature bolting where stress relaxation over service life is a critical design parameter.
Always state the heat treatment type explicitly in your engineering drawing and purchase order (e.g., "ASTM B637 UNS N07750 Type 1"). Receiving X750 in the wrong heat treatment condition — even from a capable manufacturer — produces components that fail below design temperature or exhibit inadequate creep life. This is the most frequent source of costly field failures with nickel superalloy components.
All three heat treatment types are available on our custom Inconel X750 forged parts — specify your required AMS or ASTM type when requesting a quote.
Forging Inconel X750 — Process & Technical Challenges
Key fact: Forging is the preferred manufacturing route for structural X750 components because it produces a refined grain structure with superior fatigue strength, fracture toughness, and creep resistance compared to casting. Three forging methods are used: closed die, open die, and seamless ring rolling.
Forging produces a directional, refined grain structure by mechanically deforming the billet at elevated temperature, recrystallizing the microstructure and eliminating porosity. This results in significantly improved fatigue strength, fracture toughness, and creep life compared to cast alternatives. Three forging methods are used for X750:
- Two precision dies define near-net shape
- Excellent dimensional batch consistency
- Higher tooling cost; suited for volume
- Turbine discs, flanges, valve bodies
- Shaped between flat or simple dies
- Lower tooling cost; suited for large parts
- Greater operator skill required
- Shafts, custom billets, large discs
- Ring rolled over mandrel to final size
- Optimal circumferential grain flow
- Most efficient for ring/flange profiles
- Pressure vessel flanges, bearing races
Critical Forging Parameters for Grain Size Control
The primary technical challenge is grain size control. Inconel X750 work-hardens rapidly; inadequate deformation or incorrect forging temperature produces mixed or coarse grain structures that compromise fatigue life and notch rupture ductility. Key parameters:
| Parameter | Target Range | Consequence if Violated |
|---|---|---|
| Forging temperature | 1,020 – 1,120°C | Too low: forging cracks. Too high: grain coarsening, loss of properties |
| Temperature uniformity | ±15°C through billet cross-section | Hot spots → localized grain growth → inconsistent properties |
| Strain rate | Controlled by press speed selection | Excessive rate → adiabatic shear bands |
| Reduction ratio | Minimum 4:1 recommended | Insufficient reduction → unrecrystallized coarse grains |
| Post-forge cooling | Controlled per heat treatment type | Uncontrolled cooling → microcracking or incorrect phase formation |
Professional forge shops use real-time thermocouple monitoring and controlled hydraulic press speeds to maintain billet temperature uniformity. At Jiangsu Liangyi Co., Limited, our technical team provides full CNC machining, controlled heat treatment, and EN 10204 3.1/3.2 material certification with every Inconel X750 forging shipment.
Corrosion & Oxidation Resistance
Key fact: The 14–17% chromium content of Inconel X750 forms a self-repairing Cr₂O₃ (chromium oxide) passive film that provides excellent oxidation resistance to approximately 980°C and good corrosion resistance in both oxidizing and reducing environments.
| Environment | Performance Rating | Technical Notes |
|---|---|---|
| Oxidizing atmospheres (air, O₂) | Excellent to 980°C | Self-repairing Cr₂O₃ scale; limits further oxidation |
| Reducing atmospheres (H₂, CO) | Good | Superior to most stainless grades in reducing conditions |
| Chloride environments (Cl⁻) | Good (fully aged) | Excellent SCC resistance when fully precipitation-hardened |
| Seawater / marine | Good | Significantly better than 316L stainless; suitable for offshore fasteners |
| Sulfur-bearing gases at temperature | Moderate — evaluate | Risk of nickel sulfide formation at grain boundaries above ~650°C |
| Strong mineral acids (HCl, H₂SO₄) | Limited — not recommended | Use Hastelloy C-276 or Alloy 625 for concentrated strong acid service |
| Steam environments | Good | Widely used in nuclear steam generator components |
Industrial Applications of Inconel X750 Forgings
Key fact: Inconel X750 is used in six primary industries: aerospace (turbine blades, engine casings), nuclear energy (reactor core components), power generation (gas turbine discs), space/rockets (thrust chambers), oil & gas (downhole tools), and industrial (high-temperature springs and bolts).
We supply Inconel X750 forgings for all six industries above, including forged discs, rings, bars, and custom-shape components with full EN 10204 3.1/3.2 certification and 24-hour quotation.
Inconel X750 vs Inconel 718 — Side-by-Side Comparison
Key fact: Inconel X750 has better high-temperature creep performance and relaxation resistance; Inconel 718 has higher room-temperature tensile strength and far better weldability. Select X750 for springs, bolts, and sustained creep service; select 718 for welded structures and maximum room-temperature strength.
| Property / Factor | Inconel X750 (N07750) | Inconel 718 (N07718) |
|---|---|---|
| Max creep service temperature | 700°C (1,290°F) Higher ✓ | 650°C (1,200°F) |
| Room-temperature UTS | ~1,200 MPa | ~1,380 MPa Higher ✓ |
| Stress relaxation resistance | Excellent Preferred ✓ | Good |
| Weldability | Limited — strain-age cracking risk | Excellent Industry benchmark ✓ |
| Machining difficulty | Rating 16 (moderate) | Rating 12–15 (similar) |
| Material cost | Lower More economical ✓ | Higher (Nb/Ta content) |
| Cryogenic performance | Excellent (to −250°C) Better ✓ | Good |
| Primary applications | Springs, fasteners, turbine rings, nuclear | Turbine discs, shafts, structural airframe |
| AMS Specifications | 5667, 5668, 5598 | 5662, 5663, 5664 |
Choose Inconel X750 when: the primary requirements are relaxation resistance, creep life above 650°C, cryogenic performance, or material cost optimization. Choose Inconel 718 when: weldability, maximum room-temperature strength, or highest fatigue life are the governing design requirements.
Applicable Standards & Specifications
Key fact: The primary standard governing Inconel X750 forgings is ASTM B637 (UNS N07750). AMS 5667, 5668, and 5598 define specific heat treatment conditions. EN 10204 3.1/3.2 test reports are required for most European and international shipments.
For export and international procurement, EN 10204 3.1 and 3.2 material test reports (MTR) are required by most European, Middle Eastern, and North American customers. The 3.1 report is signed by the manufacturer's quality representative; the more demanding 3.2 report is co-signed by an accredited third-party inspection agency such as Bureau Veritas, TÜV, Lloyds Register, or SGS.
Jiangsu Liangyi Co., Limited provides full MTR documentation with every shipment, including complete third-party inspection support where required by the customer's QA program.
Frequently Asked Questions
Jiangsu Liangyi Co., Limited (est. 1997, ISO 9001:2015) is an ISO-certified manufacturer of custom Inconel X750 forged parts — including closed-die forgings, open-die forgings, and seamless rolled rings — shipped to 50+ countries. Key sourcing criteria to verify with any X750 supplier:
- ASTM B637 compliance — confirm the supplier works to the standard, not just a datasheet
- Heat treatment type control — confirm all three types (AMS 5667 / 5668 / 5598) are available in-house with controlled furnaces
- EN 10204 3.1 / 3.2 MTR — mandatory for European and international projects; confirm third-party witness inspection capability
- In-house NDT — UT, MT, and PT should be performed internally, not subcontracted
- VIM+ESR melting source — ensures ultra-clean chemistry and low inclusion content for aerospace/nuclear grades
View our full manufacturing capabilities, product range, and request a free quotation: Inconel X750 Forged Parts — UNS N07750 Manufacturer →