Inconel 617 and 718 Overview
Inconel 718 (UNS N07718)：
Inconel 617 is a nickel‑chromium‑cobalt‑molybdenum solid‑solution superalloy. Without precipitation hardening treatment, it relies on uniform alloying element distribution to maintain structural stability. It features outstanding high‑temperature oxidation resistance, hot corrosion resistance and creep resistance, and is widely used in gas turbine combustion systems, high‑temperature heat exchangers and petrochemical reforming equipment.
Inconel 617 (UNS N06617)：
Inconel 718 is a niobium‑molybdenum reinforced precipitation‑hardening nickel‑iron‑chromium alloy. It obtains ultra‑high tensile strength and yield strength through double aging heat treatment. With excellent fatigue resistance, weldability and moderate corrosion resistance, it is the most cost‑effective high‑strength superalloy for aerospace, power generation and oil & gas medium‑temperature structural parts.
Detailed comparison of Inconel 617 and Inconel 718
Detailed comparison of Inconel 617 and Inconel 718
Inconel 617 and 718 are high-performance nickel-based superalloys designed for extreme environments, but their main differences lie in their temperature range and strengthening mechanism. Inconel 617 is a solid solution-strengthened alloy with excellent creep resistance and stability, and can operate at temperatures up to 1100°C (e.g., for power plant components). Inconel 718 is a precipitation-strengthened alloy with excellent strength at lower temperatures (up to 650°C) and is commonly used in aerospace engines.
What are the advantages of Inconel 718?
Inconel 718 is a high-strength, corrosion-resistant nickel-based superalloy. It possesses excellent mechanical properties, high-temperature strength, and resistance to oxidation and corrosion. Inconel 718 is widely used in various industries, including aerospace, oil and gas, automotive, and power generation.
inconel 617 vs inconel 718：Comparison of chemical properties
|
Inconel 617 (%) |
Inconel 718 (%) |
|---|---|
|
Balance (≈44.5) |
50.0 – 55.0 |
|
20.0 – 24.0 |
17.0 – 21.0 |
|
10.0 – 15.0 |
≤1.0 |
|
8.0 – 10.0 |
2.8 – 3.3 |
|
– |
4.75 – 5.50 |
|
≤3.0 |
Balance (>18%) |
|
0.8 – 1.5 |
0.2 – 0.8 |
|
≤0.6 |
0.6 – 1.15 |
|
0.05 – 0.15 |
≤0.08 |
Key Differences
INCONEL 617 contains cobalt and a high amount of molybdenum, making it a material with excellent high-temperature oxidation resistance and creep resistance.
INCONEL 718 uses niobium, titanium, and aluminum, and can achieve extremely high strength at lower temperatures through precipitation hardening.
inconel 617 vs inconel 718：Comparison of mechanical properties
| Property | INCONEL 617 | INCONEL 718 |
|---|---|---|
| Density | 8.36 g/cm³ | 8.19 g/cm³ |
| Tensile Strength (Room Temp) | 890 MPa | 1375 MPa |
| Yield Strength (0.2% offset) | 440 MPa | 1100 MPa |
| Elongation | 45% | 30% |
| Hardness (HRC) | ~25 | 35–40 |
| Maximum Service Temperature | 1100°C | 700°C |
| Creep Resistance | Excellent | Moderate |
| Fatigue Resistance | Good | Excellent |
Analysis:
Inconel 617 exhibits excellent performance at extremely high temperatures (up to 1100°C).
Inconel 718 offers higher strength and fatigue resistance at medium to high temperatures (up to 700°C).
inconel 617 vs inconel 718：Corrosion & Oxidation Resistance
INCONEL 617: Inconel 617 delivers superior high‑temperature oxidation and scaling resistance up to 1100°C. It performs stably in oxidizing, carburizing and nitriding atmospheres, making it ideal for high‑temperature flue gas and thermal cycling working conditions.
INCONEL 718: Inconel 718 features excellent resistance to chloride stress corrosion cracking and marine corrosive environments. However, its precipitation strengthening phase will dissolve above 700°C, resulting in decreased strength and oxidation resistance, so it is not suitable for long‑term ultra‑high temperature service.
inconel 617 vs inconel 718：Heat Treatment, Welding & Machining
Heat Treatment Process：
Inconel 617: Solution annealing at 1175–1205°C with air cooling. No aging treatment is required. The solution state ensures optimal ductility and high‑temperature structural stability.
Inconel 718: Solution treatment at 955°C for 1 hour + air cooling; double aging treatment (720℃ holding 8h + furnace cooling to 620℃ holding 8h) to precipitate γ′/γ″ phases and maximize mechanical strength.
Welding Performance：
Inconel 617 has good weldability without mandatory post‑weld heat treatment; recommended filler metal ERNiCrCoMo‑1. Inconel 718 can be welded, but post‑weld double aging is required to recover full structural strength; recommended filler metal ERNiFeCr‑2.
Machining Feature：
Both alloys have work‑hardening characteristics. Inconel 617 is harder to machine due to stable solid‑solution structure. Inconel 718 in annealed state is more machinable, while aged state requires low‑speed cutting with hard alloy tools.
inconel 617 vs inconel 718：How to Choose?
|
Working Condition |
Recommended Alloy |
Selection Reason |
|---|---|---|
|
Long‑term service 700–1100℃700–1100℃ |
Inconel 617 |
Maintain excellent creep & oxidation resistance under ultra‑high temperature |
|
Medium temperature ≤650℃, high strength & fatigue load650℃ |
Inconel 718 |
Highest tensile & yield strength, cost‑effective for medium‑temp structural parts |
|
Cryogenic environment (-253℃ to room temperature) |
Inconel 718 |
Excellent low‑temperature toughness and structural stability |
|
High‑temperature flue gas, carburizing & oxidizing atmosphere |
Inconel 617 |
Resist high‑temperature scaling and hot corrosion |
|
Cost‑sensitive medium‑temperature conventional parts |
Inconel 718 |
No expensive cobalt element, lower comprehensive cost |
inconel 617 vs inconel 718：Industrial Applications
Applications of INCONEL 617：
INCONEL 617's exceptional high-temperature resistance and oxidation resistance make it ideal for the energy, chemical, and aerospace industries.
Typical Applications
Gas turbine components – combustion chamber linings, transition pipes, and turbine exhaust casings.
Heat exchangers – for high-temperature gas or steam environments.
Petrochemical plants – steam reforming pipes and radiant furnace components.
Aerospace – jet engine afterburners and exhaust systems.
Nuclear power – reactor internals and heat exchanger piping.
INCONEL 617's stable structure allows for long-term use at temperatures far exceeding the limits of most alloys.
Applications of INCONEL 718：
INCONEL 718 combines strength and corrosion resistance, making it one of the most widely used high-temperature alloys in the aerospace and oil and gas industries.
Typical Applications
Aerospace
Jet engine discs, shafts, and fasteners.
Turbine blades and compressor components.
Oil and Gas
Wellhead components, valves, and downhole tools.
Power Generation
Steam turbine casings and bolts.
Marine Engineering
Subsea fasteners and springs.
Industrial Equipment
Cryogenic tanks and springs for corrosive environments.
Standards and specifications for Incoenl 718 and Inconel 617
| Alloy | ASTM / ASME Specifications |
|---|---|
| INCONEL 617 | ASTM B166, B167, B168, B564 / ASME SB167 |
| INCONEL 718 | ASTM B443, B444, B446, B637 / ASME SB637 |
Conclusion
Both INCONEL 617 and INCONEL 718 are high-performance nickel-based alloys, but they have different focuses in engineering applications:
INCONEL 617 is ideal for high-temperature strength, oxidation resistance, and long-term structural stability.
INCONEL 718 is well-suited for achieving high strength, fatigue resistance, and corrosion resistance under medium- and high-temperature conditions.
With its rigorous quality control and global distribution experience, Gnee Steel continues to provide high-quality INCONEL alloys to industries seeking excellence-from aerospace turbines to power plant heat exchangers.
About Gnee Steel
Gnee Steel is a professional manufacturer of nickel-based alloys, including Nickel 201, Nickel 202, Hastelloy C-276, Hastelloy C-22, Hastelloy B, Hastelloy C-4, Inconel 600, Inconel 625, Inconel 718, Inconel X-750, Incoloy 800, Incoloy 800H/HT, Incoloy 825, Monel 400, Monel K500, and other high-temperature alloy materials. We specialize in the production and sales of alloy materials. Gnee Steel's products are widely used in aerospace, chemical, power generation, automotive, nuclear energy, and other fields, and we can provide customized alloy material solutions according to customer needs. For inquiries about alloy material prices or customized alloy material solutions, please feel free to contact us via email at ss@gneemetal.com for a quote.
