Alloy X750,Inconel X750 Other/Similar Specs,UNS N07752

Alloy X750,Inconel X750 Wire,UNS N07752

Introduction to Alloy X750 (Inconel X750 Wire, UNS N07752) – Multifunctional Precipitation-Hardening Superalloy Series

Alloy X750, commercially recognized as Inconel X750 and designated under UNS N07752, is a precipitation-hardening nickel-chromium superalloy engineered for exceptional mechanical strength, corrosion resistance, and thermal stability across a wide temperature range (-253°C to 730°C/-423°F to 1346°F). Unlike many high-temperature alloys, its unique strength (derives from) the formation of gamma-prime (γ′) precipitates (Ni₃Al, Ti) during heat treatment, enabling it to maintain high tensile and creep strength even at elevated temperatures. As specified, Alloy X750 is available in an extensive array of product forms: Bar (Round bar, Flat bar), Ribbon, Wire, Rods, Tube, Pipe, Foil, Plate, Sheet, Strip, and Forging Stock. This versatility makes it a preferred choice for critical applications in aerospace, energy, and industrial sectors where reliability under combined thermal and mechanical stress is paramount.

1. Chemical Composition (Typical, wt%)

The chemical composition of UNS N07752 complies with strict industry standards such as ASTM B637 (for nickel-alloy bars/rods), ASTM B670 (for nickel-alloy wire), and ASME SB637, ensuring consistent precipitation-hardening behavior and performance across all product forms. The typical composition is as follows:

Element

Content Range (wt%)

Function

Nickel (Ni)

70.0 - 75.0

Serves as the primary matrix element, facilitating the formation of γ′ precipitates; enhances corrosion resistance in acidic and marine environments.

Chromium (Cr)

14.0 - 17.0

Forms a protective chromium oxide (Cr₂O₃) layer, providing superior oxidation and sulfidation resistance at temperatures up to 730°C; improves resistance to pitting corrosion.

Iron (Fe)

5.0 - 9.0

Enhances hot workability (critical for forging and rolling) and reduces alloy cost without compromising precipitation-hardening efficiency.

Titanium (Ti)

2.25 - 2.75

Key element for γ′ precipitate formation (Ni₃Ti), directly contributing to high-temperature strength and creep resistance; controlled to avoid brittle intermetallic phases.

Aluminum (Al)

0.40 - 1.00

Works with titanium to stabilize γ′ precipitates, refining their size and distribution for optimal strength; improves oxidation resistance.

Niobium (Nb) + Tantalum (Ta)

0.70 - 1.20

Enhances grain boundary strength, inhibiting creep deformation and improving stress rupture performance at 650 - 730°C.

Carbon (C)

≤ 0.08

Minimized to prevent carbide precipitation at grain boundaries, which can reduce ductility and corrosion resistance; controlled to support minor grain refinement.

Manganese (Mn)

≤ 1.0

Aids in deoxidation during melting and improves cold workability for thin forms (e.g., foil, ribbon).

Silicon (Si)

≤ 0.5

Reduces oxide formation during hot processing; supports the integrity of the chromium oxide layer.

Copper (Cu)

≤ 0.5

Limited to avoid interference with γ′ precipitate formation and prevent hot cracking during fabrication.

Phosphorus (P)

≤ 0.015

Strictly controlled to prevent brittleness, especially in welded joints of tubes and pipes exposed to cyclic temperatures.

Sulfur (S)

≤ 0.015

Minimized to avoid hot cracking during forging and wire drawing; reduces corrosion susceptibility in harsh environments.

2. Physical Properties

Alloy X750 exhibits stable physical properties across its operating temperature range, with precipitation hardening enabling tailored strength for specific applications. Key properties (consistent across all product forms) are:

Property

Value

Test Condition

Density

8.28 g/cm³

Room temperature (25°C)

Melting Point Range

1390 - 1425°C

-

Thermal Expansion Coefficient

12.3 × 10⁻⁶/°C

20 - 100°C; 15.8 × 10⁻⁶/°C (20 - 700°C)

Thermal Conductivity

11.4 W/(m·K)

100°C; 19.8 W/(m·K) (700°C)

Electrical Resistivity

1.22 × 10⁻⁶ Ω·m

Room temperature (25°C); 1.48 × 10⁻⁶ Ω·m (700°C)

Modulus of Elasticity

204 GPa

Room temperature (tensile); 165 GPa (700°C)

Poisson’s Ratio

0.30

Room temperature

Curie Temperature

≈ -196°C

Below this temperature, the alloy is weakly ferromagnetic (irrelevant for most application temperatures).

Stress Rupture Strength

280 MPa

1000 hours at 650°C; 120 MPa (1000 hours at 700°C)

Hardness (After Precipitation Hardening)

30 - 35 HRC

Room temperature (typical for bars/plates); 28 - 32 HRC (for wire/foil)

3. Production Process (Tailored for Multiform Products & Precipitation Hardening)

The manufacturing of Alloy X750 requires precise control of chemistry and heat treatment to optimize precipitation hardening, alongside form-specific processing to ensure dimensional accuracy. Below is a unified production framework with key optimizations:

3.1 Raw Material Melting & Casting (Foundation for Precipitation Hardening)

Melting: High-purity raw materials (nickel, chromium, titanium, etc.) are melted via vacuum induction melting (VIM) followed by vacuum arc remelting (VAR). This dual process eliminates gaseous impurities (O₂ < 30 ppm, N₂ < 50 ppm) and ensures uniform distribution of titanium and aluminum—critical for consistent γ′ precipitate formation.

Casting: Molten alloy is cast into:

Ingots (600 - 2500 kg) for bars, rods, and forging stock.

Slabs (12 - 50 mm thick) for plates, sheets, and strips.

Blooms (100 - 300 mm diameter) for tubes and pipes.

All cast forms undergo homogenization annealing at 1120 - 1180°C for 6 - 8 hours to eliminate chemical segregation and prepare the microstructure for subsequent processing.

3.2 Form-Specific Hot & Cold Processing

3.2.1 Bars (Round/Flat), Rods, & Forging Stock

Hot Forging: Ingots are hot-forged at 1050 - 1150°C using hydraulic presses to form round bars (diameter: 10 - 350 mm) or flat bars (thickness: 5 - 100 mm, width: 20 - 400 mm). Forging stock is shaped into near-net components (e.g., turbine blades, valve bodies) via closed-die forging, with controlled cooling to avoid premature precipitation.

Hot Rolling: Smaller rods (diameter: 5 - 25 mm) are produced via hot rolling at 1000 - 1100°C, followed by air cooling.

Cold Finishing: Precision bars undergo cold drawing (round bars) or cold rolling (flat bars) to achieve tight tolerances (±0.04 mm), then undergo solution annealing (1090 - 1120°C for 30 - 60 minutes, water-quenched) to dissolve existing precipitates—preparing for subsequent precipitation hardening.

3.2.2 Plates, Sheets, Strips, & Foil

Hot Rolling: Slabs are hot-rolled at 1000 - 1100°C into plates (thickness: 4 - 120 mm) or coils (for sheets/strips). Intermediate solution annealing (1080 - 1110°C, water-quenched) is performed to maintain ductility during rolling.

Cold Rolling: Sheets (thickness: 0.4 - 5 mm) and strips (thickness: 0.1 - 1 mm, width: 10 - 300 mm) are cold-rolled in multiple passes. Foil (thickness: 0.01 - 0.1 mm) requires ultra-fine cold rolling with frequent intermediate solution annealing (1060 - 1090°C) to avoid work hardening—critical for preserving flexibility in thin gauges.

Flatness Correction: Plates and sheets undergo roller leveling to achieve flatness ≤ 0.1 mm/m, essential for aerospace component assembly.

3.2.3 Tubes & Pipes

Seamless Tubes: Blooms are extruded at 1080 - 1150°C into tube blanks (outer diameter: 20 - 200 mm, inner diameter: 10 - 180 mm), then pierced via the Mannesmann process to create seamless tubes. Cold drawing (for precision tubes) refines dimensions to outer diameter: 6 - 180 mm, wall thickness: 0.5 - 25 mm, followed by solution annealing (1090 - 1120°C, water-quenched).

Welded Tubes/Pipes: For large-diameter pipes (outer diameter > 200 mm), Alloy X750 strip is formed into a cylinder and welded via TIG welding. Post-weld solution annealing (1100 - 1130°C, water-quenched) ensures the weld zone matches the base metal’s microstructure, enabling uniform precipitation hardening.

3.2.4 Wire & Ribbon

Wire Production: Blooms are hot-rolled into wire rods (diameter: 6 - 15 mm) at 1000 - 1100°C. Wire rods are cold-drawn through diamond dies into final wire diameters (0.1 - 6 mm) with intermediate solution annealing (1060 - 1090°C, 20 - 40 minutes) to maintain ductility. This step is critical for smooth wire feeding in welding or spring manufacturing.

Ribbon Production: Wire rods or thin flat stock are cold-rolled into ribbon (thickness: 0.05 - 0.6 mm, width: 1 - 60 mm), with surface polishing (Ra ≤ 0.2 μm) to ensure uniformity for applications like electrical contacts.

3.3 Precipitation Hardening (Key Strength-Enhancing Step)

All Alloy X750 products undergo a two-step precipitation hardening process to form γ′ precipitates and achieve target strength:

Step 1 (Stabilization): Heating to 885 - 900°C for 2 - 4 hours, followed by air cooling. This step controls grain growth and initiates initial precipitate formation.

Step 2 (Aging): Heating to 700 - 730°C for 16 - 24 hours, then air cooling. This step promotes the formation of fine, uniformly distributed γ′ precipitates, maximizing tensile strength and creep resistance.

Note: For foil or thin wire, aging time is reduced to 12 - 18 hours to avoid excessive hardening and maintain flexibility.

3.4 Surface Finishing & Quality Inspection

Surface Treatment:

Bars/Rods: Grinding (Ra ≤ 0.6 μm) or polishing (Ra ≤ 0.2 μm for aerospace-grade) to remove scale and defects.

Plates/Sheets: Pickling (nitric-hydrofluoric acid solution) to eliminate oxide layers; passivation (chromate treatment) for enhanced corrosion resistance in marine or chemical environments.

Tubes/Pipes: Internal honing (for high-flow applications) and external polishing to reduce friction; welded pipes undergo weld bead grinding for smooth surfaces.

Wire/Foil: Electrochemical cleaning to remove drawing lubricants, ensuring surface purity for welding or thin-film applications.

Quality Control:

Chemical Analysis: Optical emission spectroscopy (OES) to verify titanium, aluminum, and niobium content—critical for precipitation hardening.

Mechanical Testing: Tensile strength (≥1100 MPa after aging), yield strength (≥850 MPa after aging), and elongation (≥15% after aging) to validate strength-ductility balance.

Precipitate Inspection: Transmission electron microscopy (TEM) to confirm γ′ precipitate size (5 - 10 nm) and distribution.

Non-Destructive Testing: Ultrasonic testing (for bars/plates/tubes) to detect internal defects; eddy current testing (for wire/foil) for surface flaws; pressure testing (for pipes) at 1.5× design pressure.

4. Product Applications (By Form & Industry)

Alloy X750’s combination of precipitation-hardened strength, corrosion resistance, and form versatility makes it ideal for applications requiring high performance under thermal and mechanical stress. Key applications are organized by product form:

4.1 Bars (Round/Flat), Rods, & Forging Stock

Aerospace & Defense:

Round bars: Machined into aircraft engine turbine blades, compressor discs, and rocket engine thrust chambers (resist 650 - 730°C and cyclic mechanical stress).

Forging stock: Forged into missile guidance system components and satellite structural parts (high strength-to-weight ratio and corrosion resistance in space environments).

Energy Generation: Rods machined into nuclear reactor control rod cladding (resist high-temperature coolant corrosion and radiation damage).

Industrial Machinery: Flat bars fabricated into high-temperature valve stems and pump shafts for chemical processing plants (resist acidic media and 500 - 600°C operation).

4.2 Plates, Sheets, Strips, & Foil

Aerospace:

Plates: Used to manufacture aircraft engine casings and heat exchanger shells (withstand 600 - 700°C and pressure cycling).

Sheets: Formed into exhaust system components for military aircraft (resist thermal fatigue and saltwater corrosion).

Marine Engineering: Strips welded into offshore platform structural components (resist seawater corrosion and 400 - 500°C internal heating).

Electronics: Foil (0.02 - 0.05 mm thick) used as high-temperature electrical contacts in semiconductor manufacturing equipment (operate at 450 - 550°C).

4.3 Tubes & Pipes

Energy:

Seamless tubes: Used as boiler superheater tubes in fossil fuel power plants (resist 650 - 700°C flue gas corrosion and creep deformation).

Pipes: Transport high-temperature coolant in nuclear power plants (low neutron absorption and resistance to borated water corrosion).

Chemical Processing: Welded pipes for transporting molten salts in solar thermal power plants (resist 550 - 650°C salt corrosion).

4.4 Wire & Ribbon

Aerospace: Wire (0.3 - 1.0 mm diameter) used as springs in aircraft landing gear (high fatigue strength and corrosion resistance) and as thermocouple sheaths for engine temperature monitoring.

Industrial: Ribbon formed into resistance heating coils for high-temperature furnaces (used in metal heat treatment, operate at 600 - 700°C in air).

Medical Devices: Fine wire (0.1 - 0.2 mm diameter) for surgical instruments and implantable devices (biocompatible and corrosion-resistant in bodily fluids).

Conclusion

Alloy X750 (Inconel X750 Wire, UNS N07752) is a high-performance precipitation-hardening superalloy, distinguished by its exceptional strength, corrosion resistance, and adaptability to diverse product forms. From heavy forging stock for aerospace turbines to ultra-thin foil for electronics, it meets the demands of industries where performance under combined thermal and mechanical stress is critical. Its strict manufacturing controls—especially for precipitation hardening—ensure consistent quality across all applications. For custom requirements, such as ultra-precision wire (down to 0.05 mm diameter), large-diameter seamless pipes (up to 400 mm), or tailored aging treatments for specific strength needs, specialized production processes are available to align with unique application challenges.

Packing of Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 850 gallon liquid totes Special package is available on request.