Precipitation-Hardenable Nickel-Chromium Superalloy for High-Temperature Structural Applications
Product Specification
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Standard: ASTM B637 (Bar & Forging), ASTM B670 (Plate/Sheet/Strip)
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Material Designation: Incoloy 718 / Inconel 718 / UNS N07718 / GH4169
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Tolerance: Customizable (e.g., h7-h11) upon request
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Melt Method: Vacuum Induction Melting (VIM) + Vacuum Arc Remelting (VAR)
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Available Forms & Sizes:
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Plate/Sheet/Strip: 0.5mm to 80mm thick
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Bar/Forgings: φ6mm to φ500mm diameter
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Tube/Pipe: OD φ6mm to φ530mm, wall thickness from 0.5mm
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Wire & Custom Components: Available upon request
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Chemical Composition (wt%)
| Element | Min | Max |
|---|---|---|
| Nickel (Ni) | 50.0 | 55.0 |
| Chromium (Cr) | 17.0 | 21.0 |
| Iron (Fe) | Balance | – |
| Niobium (Nb) + Tantalum (Ta) | 4.75 | 5.50 |
| Molybdenum (Mo) | 2.80 | 3.30 |
| Titanium (Ti) | 0.65 | 1.15 |
| Aluminum (Al) | 0.20 | 0.80 |
| Carbon (C) | – | 0.08 |
| Manganese (Mn) | – | 0.35 |
| Silicon (Si) | – | 0.35 |
| Sulfur (S) | – | 0.015 |
| Phosphorus (P) | – | 0.015 |
| Copper (Cu) | – | 0.30 |
| Boron (B) | – | 0.006 |
Mechanical Properties (Solution Annealed + Aged Condition)
| Property | Typical Value | Remarks |
|---|---|---|
| Tensile Strength | ≥ 1240 MPa | (Approx. ≥ 180 ksi) |
| Yield Strength (0.2% Offset) | ≥ 1030 MPa | (Approx. ≥ 150 ksi) |
| Elongation | ≥ 12% | – |
| Hardness | 30 – 40 HRC | – |
| Modulus of Elasticity | ~ 205 GPa | At Room Temperature |
Physical Properties
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Density: 8.24 g/cm³
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Melting Range: 1260 – 1320 °C
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Thermal Expansion Coefficient: ~13.0 μm/m·°C (20-100°C)
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Thermal Conductivity: ~11.4 W/m·K (100°C)
Corrosion Resistance
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Characteristics: Excellent oxidation and corrosion resistance, outstanding resistance to chloride stress corrosion cracking, and good resistance to sulfide (H₂S) attack.
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Suitable Media:
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High-temperature oxidizing atmospheres and acidic environments
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Chloride-containing media (e.g., seawater, salt spray)
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Sour (H₂S) environments in oil and gas production
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High-temperature, high-pressure water (e.g., nuclear reactor components)
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Applications
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Aerospace: Jet engine turbine disks, compressor blades, casings, combustion chamber components, high-strength fasteners, rocket engine parts.
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Power Generation: Gas turbine disks and blades, high-strength components in nuclear power equipment.
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Oil & Gas: Downhole tools, valve stems, pump shafts, flanges, piping, and reactor components for sour service (H₂S) environments.
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Industrial Products: High-performance springs, molds, extrusion screws, medical instruments (e.g., surgical tools).
Special Processing Notes
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Heat Treatment (Precipitation Hardening):
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Solution Treatment: 950-1065°C / 1-2.5 hours, rapid cool (water, oil, or air).
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Aging Treatment: 720°C±10°C / 8 hours → Furnace cool at ~50°C/hour to 620°C±10°C / Hold for 8 hours → Air cool. This process precipitates the primary strengthening phase γ”, crucial for achieving ultra-high strength.
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Hot Working: Recommended furnace temperature not exceeding 1121°C; perform forging and other hot working within 927-1010°C.
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Cold Working: Exhibits a moderate work-hardening rate in the solution-annealed condition. Cold working is possible but more challenging than with standard stainless steels.
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Welding: Offers relatively good weldability among precipitation-hardenable nickel-based superalloys. Welding in the solution-annealed condition using matching filler metals (e.g., ERNiFeCr-2) is recommended. A full solution + age heat treatment post-weld is required to restore properties.
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Machining: Considered relatively “machinable” for a precipitation-hardening superalloy. Machining is easier in the solution-annealed condition before aging than in the fully aged condition.
