Inconel 718 is a cornerstone nickel-chromium superalloy renowned for its exceptional combination of high strength, outstanding corrosion resistance, and superb fabricability, maintaining its integrity from cryogenic temperatures up to approximately 1300°F. Its unique age-hardenability and resistance to post-weld cracking make it indispensable in demanding sectors like aerospace, oil & gas, power generation, and chemical processing.
Available in a comprehensive range of product forms, including plate, sheet, bar, wire, pipe, tube, fittings, and forgings, sourcing the right Inconel 718 product requires understanding its specifications, equivalents, properties, and procurement nuances.
This guide equips you with the critical knowledge on Inconel 718 equivalents, its detailed data sheet covering composition and properties, the rationale behind its widespread use, how to effectively obtain a quote, and key takeaways for informed purchasing decisions.
Inconel 718 Equivalent
Understanding the equivalent designations for Inconel 718 is crucial for global sourcing, cross-referencing specifications, and ensuring material compliance across different regional or industry standards. While "Inconel 718" is the widely recognized trade name, the alloy is standardized under several international systems. Its Unified Numbering System (UNS) designation is N07718, serving as the universal identifier.
Within the European EN standard, it is designated as NiCr19Fe19Nb5Mo3, sometimes seen as 2.4668, though this EN number can sometimes refer to slightly different compositions, so UNS N07718 is the safest cross-ref.
Other common proprietary or national equivalents include Nicrofer 5219 Nb (VDM Metals), Haynes 718 (Haynes International), Alloy 718, W.Nr. 2.4668 (German Werkstoffnummer), GH4169 (Chinese GB standard), and NC19FeNb (French AFNOR).
Crucially, while these names point to chemically similar alloys centered around the Ni-Cr-Fe-Nb base, minor variations in exact composition limits, impurity controls, and especially the detailed thermal processing mandated by different specifications can significantly influence the final microstructure and mechanical properties, particularly strength and creep resistance at elevated temperatures.
Therefore, specifying the exact material standard, such as AMS 5663M, is always preferred over relying solely on the trade name or UNS number when procuring for critical applications.
Inconel 718 Data
An Inconel 718 data has 3 categories:
718 inconel composition:
Nickel (Ni) 50-55% (base), Chromium (Cr) 17-21%, Iron (Fe) balance (approx. 17-19%), Niobium (Nb) + Tantalum (Ta) 4.75-5.50%, Molybdenum (Mo) 2.8-3.3%, Titanium (Ti) 0.65-1.15%, Aluminum (Al) 0.2-0.8%, Cobalt (Co) ≤ 1.0%, Carbon (C) ≤ 0.08%, Manganese (Mn) ≤ 0.35%, Silicon (Si) ≤ 0.35%, Copper (Cu) ≤ 0.30%, Phosphorus (P) ≤ 0.015%, Sulfur (S) ≤ 0.015%, Boron (B) ≤ 0.006%. The critical interaction of Nb, Ti, and Al forms the strengthening gamma-double-prime (γ'') phase during aging.
718Physical Properties:
718 inconel density: 8.19 g/cm³ (0.296 lb/in³)
718 inconel melting point: 1260-1340 ℃
718 inconel specific heat capacity: 435 J/kg·K at 20°C
718 inconel thermal expansion coefficient: 13.0 μm/m·°C (7.2 μin/in·°F) from 20 to 100°C
718 inconel themal conductivity: 11.4 W/m·K at 100°C
718 inconel electrical resistivity: 128 μΩ·cm at 20°C
718 inconel magnetism: very low (<1.01) in the annealed condition
Mechanical Properties:
Typical room-temperature mechanical properties:
Tensile Strength: ≥ 1350 MPa (195 ksi)
Yield Strength: ≥ 1170 MPa (170 ksi)
Elongation: ≥ 12%
Reduction in Area: ≥ 15%.
Hardness: 35-45 HRC.
Inconel 718 Properties
The dominance of Inconel 718 stems from its superior and well-balanced portfolio of properties:
Exceptional High-Temperature Strength: Its primary advantage is retaining high tensile, yield, creep, and stress rupture strength at temperatures up to 1300°F (704°C). The precipitation-hardening γ'' phase provides remarkable strength, significantly outperforming many stainless steels and even some other nickel alloys in this range.
Outstanding Corrosion Resistance: Resists a wide range of severe corrosive environments, including oxidation up to 1800°F (980°C) in intermittent service, excellent pitting and crevice corrosion resistance, good resistance to chloride-ion stress-corrosion cracking, and fair resistance to sulfuric and phosphoric acids under reducing conditions. Resistance to marine atmospheres and saltwater is excellent.
Super Fabricability and Weldability: Uniquely among high-strength superalloys, Inconel 718 exhibits excellent weldability by common techniques without significant post-weld heat treatment cracking, due to its sluggish age-hardening response. It can be readily forged, formed, and machined.
Excellent Fatigue Resistance: Demonstrates very good high-cycle and low-cycle fatigue strength, crucial for rotating parts and components subject to vibrational stresses.
Cryogenic Toughness: Maintains excellent ductility and toughness down to cryogenic temperatures, making it suitable for LNG and space applications.
How to Get a Quote for Inconel 718?
Obtaining an accurate and timely quote for Inconel 718 requires providing suppliers with precise information. Here's what you need to specify:
Exact Alloy and Specification: Clearly state "Inconel 718" and the mandatory governing material specification, such as AMS 5663 for bar, AMS 5596 for sheet, ASTM B637 for bar, and ASTM B670 for plate.
Product Form and Dimensions: Specify the form, like Plate, Sheet, Bar, Wire, Tube, Pipe, Forging, fitting and provide precise dimensions (e.g., Thickness x Width x Length for plate/sheet, Diameter x Length for bar, or OD x Wall x Length for tube/pipe). Include tolerances if critical.
Quantity: Provide the required quantity, such as number of pieces, total weight, or total length/area.
Heat Treatment Condition: Specify the required condition, such as solution annealed, solution annealed & aged per AMS 5662/5663, annealed, or stress relieved. For aged conditions, ensure it matches the chosen spec.
Certification Requirements: Indicate the necessary test reports, such as the Mill Test Certificate to EN 10204 3.1, 3.2, or AS 9100 compliant certs for aerospace. Specify if a chemical analysis report and mechanical test reports are needed.
Additional Testing/Special Requirements: State any requirements beyond the standard spec, such as ultrasonic testing (UT), dye penetrant inspection (DPI), eddy current (ET), grain size control, special surface finish, or traceability needs.
Delivery Requirements: Provide the desired delivery location and time frame.
Summary
Purchasing Inconel 718 demands a thorough understanding of its specifications, global equivalents, comprehensive data sheet, and the exceptional balance of properties.
To get an accurate quote efficiently, provide suppliers with detailed information, including the precise alloy designation and governing specification, exact product form and dimensions, required quantity, heat treatment condition, necessary certifications, any special testing or processing requirements, and delivery expectations.
Armed with this knowledge, you can confidently navigate the procurement process for this essential high-performance nickel alloy.
