Nickel & Cobalt Alloys

Alloy X-750 Supply Detail

Category

  • Bar and Rod

  • Plate and Sheet

  • Strip

  • Pipe and Tube

  • Wire

  • Welding

  • Powder Material

  • Cast Products

  • Forged Products

  • Fittings

  • Fastening

    Forms & Sizes

    Round Bar:
    φ2–500 mm, 1–6 m length

    Flat/Square Bar:
    4–100 mm thickness/width

    Hex Bar:
    A/F 3–100 mm

    Hollow Bar:
    OD 20–300 mm

    Forms & Sizes

    Sheet:
    0.3–6 mm thickness

    Medium Plate:
    6–25 mm thickness

    Heavy Plate:
    25–100 mm thickness

    Forms & Sizes

    Standard Strip:
    0.05–3 mm thick,
    10–600 mm wide

    Precision strip:
    0.01–0.5 mm thick,
    tight tolerance ±0.005 mm

    Foil:
    0.005–0.1 mm thick

    Forms & Sizes

    Seamless Tube:
    OD 6–450 mm,
    WT 1–50 mm,
    1–12 m length

    Welded Tube:
    OD 10–600 mm,
    WT 1–20 mm

    Capillary Tube:
    OD 1–10 mm,
    WT 0.1–2 mm

    Forms & Sizes

    Wire Form:
    Cold Drawn Wire,
    Bright Wire,
    Spring Wire,
    Fine Wire,
    Ultra-fine Wire

    General Diameter:
    φ0.1–10 mm

    Coil Weight:
    50–500 kg,
    customizable tolerance

    Forms & Sizes

    Solid Wire:
    φ0.8–4.0 mm

    Flux-cored Wire:
    φ1.2–4.0 mm

    Welding Rod:
    φ2.0–5.0 mm

    Forms & Sizes

    Powder Form:
    AM 3D Printing Powder,
    Spherical Powder,
    Gas-atomized Powder,
    Water-atomized Powder

    Particle Size:
    10–150 μm

    Sphericity:
    ≥90% for AM grade

    Forms & Sizes

    Cast Ingot:
    φ200–800 mm

    Precision Casting:
    min wall 0.5 mm

    Cast Pipe:
    OD 100–600 mm,
    WT 10–50 mm

    Forms & Sizes

    Forged Bar:
    Φ35–500 mm

    Forged Ring:
    OD 200–2000 mm

    Forging Weight:
    1–5000 kg

    Forms & Sizes

    Fittings Form:
    Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint

    Size range:
    1/2''–24'' (DN15–DN600)

    Wall thickness:
    Sch10–Sch160, STD, XS, XXS

    Pressure Class:
    150–2500 LB

    Forms & Sizes

    Fastening Form:
    Bolt, Nut, Screw, Stud, Washer, Pin, Rivet

    Metric: M3–M64

    Imperial: #4–2.5''

    Length: 6–500 mm

Alloy X-750 Product Description

Overview

Alloy X-750 is a precipitation-hardenable nickel-chromium superalloy offering high strength and excellent corrosion and oxidation resistance over a wide temperature range. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.

Essentially the corrosion- and oxidation-resistant nickel-chromium base of alloy 600 made precipitation-hardenable by additions of aluminium and titanium, Alloy X-750 develops its strength from the gamma-prime (γ′, Ni₃(Al,Ti)) phase during ageing. It provides high strength up to about 700 °C (1300 °F) — with useful strength retained to about 980 °C (1800 °F) — together with excellent properties down to cryogenic temperatures, good relaxation resistance for springs, and good corrosion and oxidation resistance. It is used in the solution-treated and aged condition, with the heat-treatment schedule selected for the application (spring temper, gas-turbine or nuclear service).

Typical applications include gas-turbine components, high-temperature springs and fasteners, nuclear-reactor jet-pump beams and internals, bolts, forming tools and rocket-engine hardware.

1. Physical Properties

Property Value Unit
Density 8.28 g/cm³
Melting range 1390–1430 °C
Elastic modulus 214 GPa
Coefficient of thermal expansion (20–100 °C) 12.6 µm/m·°C
Thermal conductivity (20 °C) 12.0 W/m·K
Specific heat (20 °C) 431 J/kg·K
Structure Austenitic (FCC)

2. Chemical Composition (wt %)

Element Symbol Min % Max % Role in Alloy
Nickel Ni 70.0 Base element; γ′ matrix
Chromium Cr 14.0 17.0 Oxidation / corrosion resistance
Iron Fe 5.00 9.00 Solid-solution element
Titanium Ti 2.25 2.75 γ′ (Ni₃Ti) precipitation strengthening
Niobium Nb (+Ta) 0.70 1.20 γ′ / carbide strengthening
Aluminium Al 0.40 1.00 γ′ formation
Manganese Mn 1.00 Deoxidiser
Silicon Si 0.50 Deoxidiser
Carbon C 0.08 Carbide formation
Cobalt Co 1.00 Residual
Copper Cu 0.50 Residual

3. Mechanical Properties

Solution-treated and aged condition, typical values for UNS N07750.

Condition Property Value
Solution treated & aged Tensile strength (UTS) ≥1100 MPa (160 ksi)
Solution treated & aged 0.2% yield strength ≥690 MPa (100 ksi)
Solution treated & aged Elongation at break ≥20 %
Solution treated & aged Reduction of area ≥25 %
Solution treated & aged Hardness ~30–40 HRC

Confirm against the mill test report. Properties depend on the solution and ageing schedule selected for the application.

4. Corrosion Resistance

Environment Performance Notes
High-temperature oxidation Excellent Passivating chromium oxide
Aqueous / general Good Chromium-bearing
Steam / nuclear water Good Note SCC risk in high-temperature pure water
Cryogenic Excellent Retains strength and toughness
Relaxation (springs) Excellent Maintains spring force at temperature

Corrosion and oxidation resistance is good across a wide temperature range; in high-temperature pure water (e.g. reactor service) attention must be given to intergranular stress-corrosion cracking and the appropriate heat treatment selected.

5. Heat Treatment

A γ′ precipitation-hardenable superalloy; strengthened by solution treatment followed by ageing. The schedule is chosen for the application.

Solution Treatment Solution anneal at approximately 1095–1150 °C (for maximum creep-rupture strength) or ~980 °C for spring and general grades, then cool.

Precipitation Hardening (Ageing) Age to precipitate γ′ (Ni₃(Al,Ti)) — for example a single age near 730 °C / ~20 h, or an equalised/double age (~885 °C then ~705 °C) for high-temperature service; spring tempers use ~650–730 °C. Select per the relevant AMS specification.

6. Weldability and Joining

Weldable by inert-gas processes; welding is generally done in the solution-annealed condition with post-weld solution and ageing. As a γ′ alloy it requires care to avoid strain-age cracking.

Welding Process Applicability Filler / Consumable
GTAW / TIG Acceptable Matching X-750 / compatible filler
GMAW / MIG Acceptable Matching filler
Resistance / spot Good

Weld in the solution-annealed condition; apply post-weld solution and ageing to develop properties.

7. Machinability and Fabrication

Machining Guidelines

Parameter Recommendation
Preferred condition Solution-annealed for machining, then age
Machinability Difficult; rigid setups, carbide tooling, slow speeds
Coolant Ample coolant

Forming Processes

Process Notes
Cold forming In the annealed condition; work-hardens; spring tempers cold-coiled
Hot forming Performed hot; solution and age afterward

8. Applications

Industry Typical Components Key Requirements
Gas turbine Blades, discs, rings, bolts Strength + oxidation resistance
Springs / fasteners High-temperature springs, bolts Strength + relaxation resistance
Nuclear Jet-pump beams, internals, springs Strength + controlled SCC behaviour
Aerospace / cryogenic Rocket hardware, cryogenic parts Strength across temperature range

9. Available Product Forms and Standards (ASTM / AMS System)

Product Form ASTM Standard AMS
Bar, rod and wire ASTM B637 AMS 5667 / 5668 / 5671
Spring wire and strip ASTM B637 AMS 5698 / 5699
Forgings ASTM B637 AMS 5670
Material designation UNS N07750 AMS 5667 / 5668 / 5670

Nickel-chromium precipitation-hardenable superalloy. UNS N07750.

10. Comparison with Related Alloys (Alloy Designation System)

Alloy Ni % Cr % Strengthening Best Used For
Alloy X-750 ≥70 14–17 γ′ (Al, Ti) Springs, bolts, fasteners; corrosion + high strength to ~700 °C
Alloy 600 ≥72 14–17 Solid solution General-purpose Ni-Cr-Fe alloy (X-750 base)
Alloy 718 50–55 17–21 γ′ + γ″ (Nb, Ti) Most-used high-strength superalloy
Alloy 90 (Nimonic) Balance 18–21 γ′ (Al, Ti) Gas-turbine blades and rings
Alloy 751 ≥70 14–17 γ′ (Al, Ti) Higher-Ti X-750 variant; exhaust valves

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