Hangbo Alloy Group
Shanghai · Est. 2012
UNS N07718 / W.Nr. 2.4668 — Precipitation-hardening nickel superalloy with outstanding tensile strength, fatigue resistance, and creep-rupture properties up to 700°C.
Inconel 718 (UNS N07718 / W.Nr. 2.4668) is a precipitation-hardenable nickel-chromium superalloy strengthened primarily by gamma double-prime (Ni3Nb) and gamma-prime (Ni3(Al,Ti)) phases. Developed in the late 1950s for gas turbine engine components, it has become the most widely used superalloy in aerospace, power generation, and high-performance oil & gas equipment. The alloy retains high strength, excellent creep resistance, and good fatigue life at temperatures up to approximately 700°C (1300°F), making it the material of choice for critical rotating and structural components.
What distinguishes Inconel 718 from many other age-hardenable nickel alloys is its exceptional weldability and formability in the annealed condition. Unlike alloys such as Waspaloy or Rene 41, Inconel 718 does not suffer from strain-age cracking during welding or post-weld heat treatment, which dramatically reduces fabrication costs and improves reliability in complex assemblies. Its sluggish precipitation kinetics allow it to be welded without cracking in a wide range of section thicknesses.
The alloy's balanced chemistry includes significant additions of niobium, molybdenum, titanium, and aluminum. Niobium is the primary strengthening element, forming the metastable gamma double-prime phase that provides high strength without excessive loss of ductility. Chromium contributes oxidation and corrosion resistance, while molybdenum and niobium together improve resistance to pitting and crevice attack in chloride-containing environments. Iron is intentionally controlled at lower levels to optimize mechanical stability and thermal response.
The processing route for Inconel 718 typically begins with vacuum induction melting (VIM) followed by vacuum arc remelting (VAR) or electroslag remelting (ESR) to achieve the cleanliness and consistency required by aerospace and energy specifications. The alloy is hot worked in the 950-1150°C range, with care taken to avoid overheating that could produce coarse grain or harmful Laves phase. Cold working is feasible in the annealed condition, although the alloy work-hardens rapidly and may require intermediate anneals for severe forming operations.
Machining Inconel 718 in the aged condition is challenging because of its high strength and tendency to work-harden. Carbide or ceramic cutting tools, rigid setups, low cutting speeds, and generous coolant flow are essential for good tool life and surface finish. Many aerospace suppliers prefer to rough machine in the annealed condition, apply the final age hardening treatment, and then perform finish machining to tight tolerances. Welding is readily accomplished using gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and electron beam welding (EBW) with matching filler metal ERNiFeCr-2.
At Hangbo Alloy Group, Inconel 718 is supplied in solution-annealed and aged conditions per AMS 5662, AMS 5663, ASTM B637, and custom aerospace specifications. We produce round bars, forgings, seamless tubes, plates, and precision-machined components for turbine manufacturers, downhole tool builders, and racing-motor suppliers worldwide.
The chemistry of Inconel 718 is tightly specified to balance strength, weldability, and thermal stability. The niobium content is critical: it must be high enough to form sufficient gamma double-prime during aging, yet not so high as to promote detrimental delta phase or Laves phase formation. Carbon, sulfur, phosphorus, and boron are restricted to protect ductility and creep rupture life.
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | 50.0 | 55.0 |
| Chromium (Cr) | 17.0 | 21.0 |
| Iron (Fe) | Balance | Balance |
| Niobium + Tantalum (Nb+Ta) | 4.75 | 5.50 |
| Molybdenum (Mo) | 2.80 | 3.30 |
| Titanium (Ti) | 0.65 | 1.15 |
| Aluminum (Al) | 0.20 | 0.80 |
| Cobalt (Co) | — | 1.00 |
| Carbon (C) | — | 0.08 |
| Manganese (Mn) | — | 0.35 |
| Silicon (Si) | — | 0.35 |
| Phosphorus (P) | — | 0.015 |
| Sulfur (S) | — | 0.015 |
| Boron (B) | — | 0.006 |
| Copper (Cu) | — | 0.30 |
Inconel 718 has a face-centered cubic (FCC) austenitic matrix in the solution-annealed condition. Upon aging, coherent gamma double-prime precipitates form uniformly throughout the matrix, producing high strength with minimal distortion. The alloy maintains a relatively low thermal expansion coefficient compared to steels and has moderate thermal conductivity, which helps reduce thermal fatigue in cyclic applications.
| Property | Value | Unit |
|---|---|---|
| Density | 8.19 | g/cm3 |
| Melting Range | 1260 - 1336 | °C |
| Specific Heat (21°C) | 435 | J/kg·K |
| Thermal Conductivity (21°C) | 11.4 | W/m·K |
| Electrical Resistivity (21°C) | 1.25 | μΩ·m |
| Modulus of Elasticity (21°C) | 205 | GPa |
| Mean Coefficient of Thermal Expansion (21-93°C) | 13.0 | μm/m·°C |
| Curie Temperature | -143 | °C |
Mechanical properties of Inconel 718 depend strongly on heat treatment. The standard aerospace heat treatment consists of solution annealing at approximately 954-980°C, followed by a two-step age: 718°C for 8 hours, furnace cool to 621°C, hold 8 hours, then air cool. This produces the optimum combination of tensile strength, yield strength, fatigue resistance, and creep life. The values below are typical for bars and forgings in the aged condition per AMS 5663.
| Property | Value |
|---|---|
| Tensile Strength | 1275 MPa (185 ksi) |
| Yield Strength (0.2% offset) | 1035 MPa (150 ksi) |
| Elongation in 2 inches | 12 - 20% |
| Reduction of Area | 15 - 35% |
| Hardness | 36 - 47 HRC |
| Charpy V-notch Impact (room temp) | 30 - 50 J |
Inconel 718 is supplied in either solution-treated (AMS 5662) or solution-treated plus aged (AMS 5663) condition. Solution treatment dissolves the strengthening phases and produces a soft, workable microstructure. Aging precipitates the gamma double-prime and gamma-prime phases that give the alloy its high strength. Two common heat treatment schedules are used:
Careful control of heating rate, furnace atmosphere, and quenching medium is essential to avoid distortion, surface oxidation, and unwanted phase formation. Hangbo Alloy Group provides material with full heat treatment certification and can perform NDT inspection including ultrasonic testing, dye penetrant inspection, and radiography on request.
Inconel 718 was specifically developed to maintain high strength at elevated temperatures. Its strength retention is superior to solid-solution alloys because of the coherent gamma double-prime precipitates, which remain stable up to about 650°C and contribute to creep resistance. Above 700°C, the precipitates begin to coarsen and transform to equilibrium delta phase, causing gradual strength loss. Short-term exposure to 870°C is possible, but long-term service is normally limited to 650-700°C depending on stress and life requirements.
| Temperature (°C) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 21 (Room) | 1275 | 1035 | 18 |
| 316 | 1195 | 965 | 19 |
| 427 | 1140 | 930 | 19 |
| 538 | 1070 | 895 | 18 |
| 649 | 930 | 795 | 20 |
| 704 | 725 | 620 | 24 |
| 760 | 510 | 440 | 30 |
| 816 | 310 | 275 | 42 |
Although Inconel 718 is primarily selected for mechanical properties rather than corrosion resistance, it performs well in many aggressive environments thanks to its high chromium and molybdenum content. The alloy is not a substitute for Hastelloy C-276 in strongly reducing acids, but it offers excellent service in oxidizing and mildly reducing media at moderate temperatures.
The combination of high strength, good fabricability, and temperature capability makes Inconel 718 one of the most versatile superalloys in modern engineering. It is used in both static and rotating components where reliability under stress and temperature is non-negotiable.
Hangbo Alloy Group manufactures and supplies Inconel 718 in a comprehensive range of product forms and sizes, all supported by material test reports and third-party inspection. Our typical supply scope includes:
| Standard | Description |
|---|---|
| ASTM B637 | Bar, Forging, and Forging Stock |
| AMS 5662 | Bar, Forging, and Ring, Solution Treated |
| AMS 5663 | Bar, Forging, and Ring, Solution & Aged |
| AMS 5596 | Sheet, Strip, and Plate, Solution & Aged |
| AMS 5597 | Sheet, Strip, and Plate, Solution Treated |
| AMS 5589 | Seamless Tubing, Solution & Aged |
| AMS 5590 | Seamless Tubing, Solution Treated |
| AWS A5.14 | Welding Wire (ERNiFeCr-2) |
| ASME SB-637 | Boiler and Pressure Vessel Code |
Hangbo Alloy Group maintains mill-direct supply of Inconel 718 round bars, forgings, tubes, and plates in both AMS 5662 and AMS 5663 conditions. Our team can assist with material selection, heat treatment specification, NDT requirements, and export documentation. We support customers in aerospace, oil & gas, power generation, and motorsport industries with reliable quality and fast delivery.
For quotations, material certifications, or technical consultation, contact our sales team or call +86-136-1165-6360. We typically respond within 10 minutes.
Request a quotation for Inconel 718 round bars, forgings, tubes, or plates. We stock standard sizes and accept custom orders.