Inconel 625 and Inconel 718 serve distinct high‑temperature scenarios. Inconel 718 gains strength via precipitation hardening, delivering superior tensile and yield strength below 700 °C, ideal for high‑load structural parts. Inconel 625 adopts solid‑solution strengthening. It outperforms 718 in long‑term oxidation resistance above 700 °C, maintains stable performance at higher service temperatures, and features broader corrosion resistance against acidic and seawater environments, with simpler welding without post‑weld aging. Choose 718 for room‑to‑moderate‑temperature high strength; pick 625 for extreme heat and harsh corrosive conditions.
Inconel 625 Marked Pipe Photo
What is Inconel 625 (UNS N06625)?
Inconel 625 is a nickel-chromium-molybdenum-niobium alloy registered as UNS N06625 (W.Nr.2.4856, DIN NiCr22Mo9Nb). It is a solid-solution strengthened alloy known for its outstanding corrosion resistance and high strength without precipitation hardening. The alloy conforms to ASTM B446 (bar), B443 (plate), B444 (tube), and B564 (forging) standards.
Key characteristics include excellent fatigue strength, oxidation resistance up to 980°C, and resistance to pitting, crevice corrosion, and stress-corrosion cracking. Is Inconel a nickel alloy? Yes - Inconel 625 contains ≥58% nickel, making it a true nickel-based alloy suitable for marine, chemical processing, aerospace, and nuclear applications.
What is Inconel 718 (UNS N07718)?
Inconel 718 is a precipitation-hardening nickel-chromium-iron alloy registered as UNS N07718 (W.Nr.2.4668, DIN NiCr19Fe19Nb5Mo3). It derives its ultra-high strength from age-hardening via gamma double-prime (Ni&sub3;Nb) precipitates. The alloy conforms to ASTM B670 (plate), B637 (bar), and AMS 5662 (bar) standards.
Inconel 718 is the most widely used superalloy in aerospace, accounting for over 30% of turbine engine weight. It offers excellent tensile and creep-rupture properties from -250°C to 700°C. After solution treatment and aging, tensile strength can exceed 1240 MPa - nearly double that of Inconel 625.
Inconel 625 vs Inconel 718: Chemical Composition Comparison
The inconel alloy composition differences between these two grades explain their divergent properties. Inconel 625 has higher Cr and Mo for corrosion resistance, while Inconel 718 has higher Fe and Nb for precipitation strengthening.
| Element | Inconel 625 (N06625) | Inconel 718 (N07718) |
|---|---|---|
| Ni | ≥58.0 | 50.0 – 55.0 |
| Cr | 20.0 – 23.0 | 17.0 – 21.0 |
| Mo | 8.0 – 10.0 | 2.8 – 3.3 |
| Fe | ≤5.0 | Balance |
| Nb | 3.15 – 4.15 | 4.75 – 5.50 |
| Ti | ≤0.40 | 0.65 – 1.15 |
| Al | ≤0.40 | 0.35 – 0.80 |
| C | ≤0.10 | ≤0.08 |
The inconel alloy 625 chemical composition features 8–10% Mo and 3.15–4.15% Nb for solid-solution strengthening and pitting resistance. The inconel alloy 718 chemical composition uses 4.75–5.50% Nb plus Ti and Al for precipitation hardening, yielding much higher strength but slightly lower corrosion resistance.
Inconel 625 vs Inconel 718: Mechanical Properties and Strength
The inconel alloy properties comparison shows a dramatic difference in strength. Inconel 718 in the aged condition has nearly double the tensile strength of Inconel 625, while Inconel 625 offers better ductility and toughness.
| Property | Inconel 625 (Annealed) | Inconel 718 (Solution + Aged) |
|---|---|---|
| Tensile Strength, MPa | ≥655 | ≥1240 |
| Yield Strength (0.2%), MPa | ≥310 | ≥1034 |
| Elongation, % | ≥30 | ≥12 |
| Hardness, HB | ≤220 | ≤331 (33–40 HRC) |
| Density, g/cm³ | 8.44 | 8.19 |
| Melting Range, °C | 1290 – 1350 | 1260 – 1336 |
Inconel 718 achieves its ultra-high strength through a two-step heat treatment: solution annealing at 980°C followed by double aging at 720°C and 620°C. This precipitation of gamma double-prime phase is the key difference - nickel alloy 625 vs inconel 625 refers to the same material, while 718 is fundamentally different in strengthening mechanism.
Corrosion Resistance: Inconel 625 vs Inconel 718
Inconel 625 (UNS N06625) contains higher levels of Mo (8.0–10.0%) and Cr (20.0–23.0%), delivering markedly superior corrosion resistance. It offers outstanding resistance to pitting corrosion, crevice corrosion and intergranular corrosion, and performs well in both oxidizing and reducing media.
Inconel 718 (UNS N07718) has a lower molybdenum content of 2.8–3.3%, making it more susceptible to pitting corrosion in chloride‑containing environments. It still maintains good overall corrosion resistance and provides strong resistance to chloride‑induced stress corrosion cracking (SCC).
| Corrosion Type | Inconel 625 | Inconel 718 |
|---|---|---|
| Pitting Resistance | ★★★★★ | ★★★ |
| Crevice Corrosion | ★★★★★ | ★★★ |
| Stress Corrosion Cracking | ★★★★★ | ★★★★★ |
| Oxidation Resistance | ★★★★★ | ★★★★ |
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Inconel 625 vs Inconel 718：Welding Performance Comparison
Inconel 625 has excellent weldability. It is a solid-solution alloy with no precipitation-hardening phase, so it does not require post-weld heat treatment and is not prone to strain-age cracking. Common processes include GTAW, GMAW, and SMAW.
Inconel 718 is also weldable but more challenging due to its precipitation-hardening nature. It is susceptible to weld cracking, particularly micro-fissuring in the heat-affected zone. Post-weld solution treatment and aging are typically required to restore full properties.
Inconel 625 vs Inconel 718：Price and Economy
The inconel alloy price depends on raw material costs, processing complexity, and market demand. Inconel 625 is generally more affordable than Inconel 718 due to simpler heat treatment (solution annealed only) and wider availability.
Inconel 718 commands a premium because it requires controlled precipitation hardening, has stricter quality requirements for aerospace applications, and demands more complex machining. For non-aerospace applications, Inconel 625 often provides better value.
| Factor | Inconel 625 | Inconel 718 |
|---|---|---|
| Relative Price | Lower | ~30–50% Higher |
| Heat Treatment Cost | Low (annealed only) | High (solution + aging) |
| Machining Cost | Moderate | High |
| Availability | Wide (stock available) | Aerospace-certified sources |
How to Choose Between Inconel 625 and 718
Use this quick selection guide to determine which inconel alloy is right for your application:
- ✓ Choose Inconel 625 for marine, chemical processing, pollution control, nuclear, and oil & gas applications where corrosion resistance is the priority.
- ✓ Choose Inconel 718 for aerospace turbine components, rocket motors, fasteners, and high-stress structural parts requiring ultra-high strength.
- ✓ Choose Inconel 625 when weldability is critical and post-weld heat treatment is not feasible.
- ✓ Choose Inconel 718 for service temperatures requiring sustained strength above 600°C with creep resistance.
- ✓ Choose Inconel 625 when budget is a constraint and ultra-high strength is not required.
Why Choose GNEE Alloy as Your Supplier Partner?
As an ISO & CE certified nickel based alloy supplier, we provide both Inconel 625 and Inconel 718 products with full quality documentation:
- ✓ Full product range: Plate, sheet, bar, pipe, fittings, and forgings per ASTM B446/B443 (625) and B670/B637 (718)
- ✓ Stock ready: Over 500 tons of Inconel 625 and 718 in standard sizes, shipment within 30 days
- ✓ Quality assurance: EN 10204 3.1 MTC, chemical composition report, mechanical test report, NDT report
- ✓ Third-party inspection: SGS, BV, TÜV supported
- ✓ OEM customization: Custom dimensions and specifications based on your drawings
Contact us for the latest export price quote for Inconel 625
FAQ:
Q: Is alloy 625 the same as Inconel 625?
A: Yes. "Alloy 625" and "Inconel 625" refer to the same material - UNS N06625. Inconel is the Special Metals Corporation trade name; "alloy 625" is the generic designation used in ASTM standards. The difference between alloy 625 and inconel 625 is only the name.
Q: What is the difference between nickel alloy and Inconel?
A: Inconel is a specific family of nickel-chromium-based superalloys. "Nickel alloy" is a broader category. Difference between nickel alloy and inconel is that Inconel alloys (625, 718, 600, etc.) are specific grades with defined compositions under the Inconel trade name, while nickel alloy covers all nickel-based materials.
Q: Is Inconel 718 stronger than Inconel 625?
A: Yes. In the aged condition, Inconel 718 has a tensile strength of ≥1240 MPa versus ≥655 MPa for Inconel 625 - nearly double. However, Inconel 625 has better ductility and corrosion resistance.
Q: Can Inconel 625 be welded to Inconel 718?
A: Yes, using Inconel 625 filler wire (ERNiCrMo-3). The dissimilar weld is common in oil and gas applications where 625 is used as a weld overlay on 718 components. Post-weld heat treatment should be considered based on service requirements.
Q: What metals are in Inconel?
A: The main metals in Inconel alloys are nickel, chromium, iron, molybdenum, niobium, cobalt, titanium, and aluminum. What metals are in inconel varies by grade - Inconel 625 has high Mo (8–10%), while Inconel 718 has high Nb (4.75–5.50%) and Ti/Al for precipitation hardening.
