Inconel 625 and Inconel 718, widely known as Alloy 625 and Alloy 718, fall under the nickel-based superalloy category and belong to the Inconel alloy series. That said, what key distinctions separate Inconel 625 from Inconel 718?
This guide dissects the core gaps between Inconel 625 and 718, covering chemical makeup and industry-specific application scenarios. Before diving into comparative analysis, we clarify key naming terminology for quick reference.
Terminology Explanation：
You will see us alternate between "Inconel 625" and "Alloy 625" across this page. To spare you extra research on the two labels, we outline their relationship upfront.
Inconel 625 and Alloy 625 denote the identical material. Inconel is an officially registered trademark owned by Special Metals Corporation. For trademark compliance, most metal distributors and steel vendors adopt the neutral designation "Alloy 625" in formal quotations and datasheets.
Inconel 625 & 718 Seamless Pipe & Hollow Section
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Inconel 625 vs Inconel 718：Differences in chemical composition
Inconel 625 (UNS N06625, trade name Alloy 625) relies on molybdenum and niobium alloyed within its nickel-chromium base for solid-solution strengthening, delivering stable mechanical performance across variable temperature ranges.
In contrast, Inconel 718 (UNS N07718, trade name Alloy 718) is a precipitation-hardening superalloy. Its high iron, niobium and molybdenum content, paired with minor aluminum and titanium, forms nano-scale precipitates after controlled thermal processing. These precipitates hinder matrix dislocation movement, granting Alloy 718 substantially higher yield and ultimate tensile strength than Alloy 625.
| Element | Ni | Cr | Fe | Nb | Mo | Ti |
|---|---|---|---|---|---|---|
| Inconel 625 | 58 Min | 20 – 23 | 5 Max | 3.15 – 4.15 | 8 – 10 | 0.4 Max |
| Inconel 718 | 50 – 55 | 17 – 21 | ~ 17 | 4.75 – 5.5 | 2.8 – 3.3 | 0.65 – 1.15 |
Summary：
- Inconel 625 gains strength mainly from solid-solution strengthening.
- Inconel 718 gains strength through precipitation hardening, which provides much higher mechanical performance.
Inconel 625 vs Inconel 718：Differences in mechanical properties
| Property | Inconel 625 | Inconel 718 |
|---|---|---|
| Strengthening Method | Solid Solution | Precipitation Hardening |
| Tensile Strength | ~ 930 MPa | ~ 1375 MPa |
| Yield Strength | ~ 517 MPa | ~ 1100 MPa |
| Elongation | ~ 30% | 12 – 20% |
| Hardness | ~ 220 HB | ~ 330 HB |
| Max Service Temp | Up To 980℃ (1796℉) | Up To 700 – 750℃ (1292 – 1382℉) |
| Corrosion Resistance | Excellent (especially marine) | Very Good (less than 625) |
| Weldability | Outstanding | Good (requires care) |
Summary：
- Inconel 718 delivers far superior yield and tensile strength via precipitation hardening yet has limited forming flexibility. By contrast, solid-solution strengthened.
- Inconel 625 features outstanding ductility, enabling simpler cutting, bending and welding fabrication despite lower base mechanical strength.
Inconel 625 vs Inconel 718：Corrosion Resistance vs Mechanical Performance
Inconel 625: Corrosion-Resistant Solid-Solution Superalloy
As a fully solid-solution strengthened nickel-chromium alloy free of high iron fractions, Alloy 625 exhibits outstanding resistance to pitting, crevice corrosion and high-temperature oxidation. It sustains stable anti-corrosion performance in seawater and harsh chemical media, making it the primary material for thin-wall tubing and complex formed fittings.
Inconel 718: High-Strength Precipitation-Hardening Superalloy
Alloy 718 achieves peak mechanical bearing capacity through precipitation hardening, retaining excellent tensile and yield strength up to 700°C (1300°F). It is specified for heavy-load fasteners, high-pressure pump shafts and heavy-duty flanges in pressure containment systems for applications under severe static and cyclic mechanical loads.
Inconel 625 vs Inconel 718：Fatigue Life and Creep Performance
Inconel 718 delivers exceptional high-temperature strength and creep resistance up to 700°C via precipitation hardening. Solid-solution strengthened Inconel 625 has good thermal stability but far inferior creep resistance, suited for low-stress high-temperature applications.
| Comparison Dimension | Inconel 625 (UNS N06625) | Inconel 718 (UNS N07718) |
|---|---|---|
| Core Strengthening Mechanism (Performance Root) | Solid-solution strengthening by molybdenum and niobium, no precipitation hardening phase | Precipitation hardening via γ'' phase formed by niobium, aluminum and titanium, with strong dislocation pinning effect |
| Long-Term Safe Operating Temperature Limit | 650°C (1200°F) | 700°C (1290°F), short-term peak up to 750°C |
| High-Temperature Strength Retention (at 650°C) | ~40-50% of room-temperature tensile strength | ~70-80% of room-temperature tensile strength, far superior high-temperature strength retention |
| Creep Resistance Rating | Moderate, applicable for low-stress conditions, fast creep deformation rate under high stress | Excellent, top-tier creep resistance among nickel-based alloys, extreme creep resistance under high-temperature and high-stress conditions |
| 1000h Creep Rupture Strength (at 650°C) | ~180 MPa | ~450 MPa, more than 2.5 times that of Inconel 625 |
| High-Temperature Microstructure Stability | Excellent, no obvious precipitate coarsening under long-term high temperature, slow performance attenuation | Stable below 700°C, rapid coarsening of γ'' phase above 700°C, sharp drop in strength and creep performance |
Talk to our metallurgical engineer to pick the right nickel superalloy for your equipment
Unsure which grade matches your project's corrosion, creep or welding requirements? Send your working temperature, pressure and medium parameters, our metallurgist will deliver a free tailored Inconel 625 / 718 material selection report within 24 hours.
Inconel 625 VS 718:Heat Treatment Protocols
Inconel 625：
Only simple solution annealing is required. This process restores the protective passive film to bring the material up to service standards with fast, straightforward operation. Inconel 625 is generally supplied in the annealed condition, delivering full performance without complex heat treatment. It features superior machinability, weldability and formability, while minimizing the risk of post-weld cracking.
Inconel 718：
Multi-stage age hardening treatment is mandatory. The procedure involves heating the alloy and holding it at precise temperatures for several hours to form precipitates that boost tensile strength. The lengthy heat treatment cycle extends the typical lead time for Inconel 718 tubular products. A rigorous heat treatment sequence (solution treatment followed by two ageing cycles) is required to unlock its maximum mechanical strength. Improper processing drastically degrades performance, so strict QC control throughout production is critical.
Inconel 625 vs Inconel 718: Comparison of Welding & Machining Performance
Solid-solution strengthened Inconel 625 features excellent weldability and machinability for all delivery states. No mandatory PWHT is required to retain full corrosion resistance, which makes it the preferred material for intricate formed and machined industrial components.
Precipitation-hardened Inconel 718 needs rigid welding control and can only be welded in solution-annealed form. Welding softens heat-affected zones; complete solid-solution plus double aging PWHT is mandatory to restore its original mechanical strength.
| Comparison Category | Inconel 625 (UNS N06625) | Inconel 718 (UNS N07718) |
|---|---|---|
| Weldability Rating | Excellent, broad process window | Good, rigorous process control required |
| Metallurgical Welding Risk | Low hot cracking, no strain-age cracking risk | Moderate solidification cracking; severe strain-age cracking if welded after aging |
| Mandatory Post-Weld Heat Treatment (PWHT) | Not required; as-welded joints retain full corrosion resistance | Mandatory solid-solution + double aging to recover tensile/yield strength |
| Allowed Welding Delivery Condition | Any delivery state | Only solution-annealed state; aging condition welding prohibited |
| Standard Filler Metal | ERNiCrMo-3 (matching base metal corrosion resistance) | ERNiFeCr-2 for strength matching; ERNiCrMo-3 for anti-corrosion service |
| Relative Machinability (vs free-cut steel=100) | ~30, moderate cutting resistance | ~25 (annealed) / ~20 (aged); faster work hardening |
| Machining Difficulty & Tool Loss | Forgiving, stable tool life, lower cutting force | High cutting load, rapid tool wear; interrupted cuts easily damage inserts |
| Forming & Cold Fabrication | Superior ductility, suitable for bending, stamping, thin-wall complex fittings | Limited formability, larger forming force, prone to springback |
| Fabrication Cost Profile | Low post-weld processing cost, mass production friendly | Extra heat treatment cycle, higher tool consumption, elevated overall manufacturing expense |
Inconel 625 vs Inconel 718：Applications
Inconel 625 Applications：
Choose Alloy 625 where corrosion resistance is the deciding factor：
- Oil and gas - subsea equipment, cladding, wellhead components in sour (H₂S) and chloride service.
- Chemical processing - heat exchangers, reactor internals, scrubber systems.
- Marine engineering - seawater piping, propeller shafts, exhaust systems.
- Aerospace - ducting, exhaust systems, engine thrust-reverser structures in corrosive environments.
- Nuclear and power - control-rod drive mechanisms, feedwater heater components.
Inconel 718 Applications
Choose Alloy 718 where high strength at elevated temperature is the deciding factor：
- Aerospace - turbine disks, blades, shafts, fasteners, casings (the dominant alloy in jet-engine rotating hardware).
- Rocket and space - cryogenic tank components, engine hardware.
- High-performance automotive - racing engine valves, turbocharger components.
- Oil and gas downhole - high-strength packers, hangers and tools where temperature stays below ~650 °C.
- Tooling - molds and dies requiring high hardness at temperature.
Inconel 625 vs Inconel 718：Product Forms and Standards
| Product Form | Inconel 625 - Governing Standard | Inconel 718 - Governing Standard |
|---|---|---|
| Plate / sheet / strip | ASTM B443 | ASTM B670 |
| Round bar / rod / wire | ASTM B446 | ASTM B637 |
| Seamless pipe & tube | ASTM B444 / B704 / B705 | ASTM B704 / B705 |
| Fittings / flanges | ASME B16.5 / B16.9 (per mill practice) | ASME B16.5 / B16.9 (per mill practice) |
As a supplier of nickel alloys, GNEE STEEL stock and produce both grades in pipe, tube, sheet, plate, round bar, wire, fittings, flanges and coil. Typical bar supply range is 3–800 mm diameter; sheet and plate from 0.5 mm thick upward.
Quick Selection Guide for Buyers
- Media is seawater, chloride, sour gas or oxidizing acid → Inconel 625.
- Part is a rotating or highly loaded component above 400 °C, or needs maximum strength-to-weight → Inconel 718 (aged).
- Long-term service above 650 °C with moderate loads → Inconel 625 (718 loses its aged strength above ~650 °C).
- Always specify the UNS number (N06625 / N07718) plus the governing ASTM standard on the PO, and require a mill test certificate.
Why Choose GNEE as Your Inconel 625 & 718 Supplier?
✅️Professional Superalloy Technical Support
With 18 years focused on Inconel 625 & 718, our metallurgical team guides grade selection, welding schemes and heat treatment plans to match your aerospace, offshore and chemical project demands precisely.
✅️In-house Full Production & Strict Quality Control
We adopt VIM+VAR double vacuum smelting, conduct full NDT inspection, and supply EN 10204 3.1/3.2 certified plates, bars and tubes, with complete batch traceability for all nickel alloy batches.
✅️Stock Inventory & One-stop Custom Fabrication
180 tons spot stock of Inconel 625 & 718 cuts delivery lead time to 7–15 days. Custom machining and heat treatment help you save total production procurement costs.
Contact us for the latest export price quote
This page covers all key gaps in corrosion resistance, high-temperature creep, weldability and mechanical strength between Inconel 625 and 718. If you cannot decide the proper grade for your chemical, marine or gas turbine equipment, fill in your dimension and working condition requirements, and we will send a full comparison quotation and technical solution free of charge.
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FAQ:
Is Inconel 625 Stronger Than Inconel 718?
No.Inconel 718 has significanty higher yield and tensile strength after heat treatment.Inconel 625 focuses more on corrosionresistance than extreme strength.
Which is Better For Piping Systems?
For corrosive environments such as offshore. chemical plants,and seawater exposure,nconel 625 pipe is often preferredFor high-pressure, high-load systems where strength is critical,inconel 718 pipe may be more suitable.
Is Inconel 718 Harder to Machine?
Yes. Due to its higher strength and work-hardening tendency,lnconel 718 is generally more challenging to machine than Inconel 625
and requires more controlled tooling and parameters.
Can Inconel 625 Replace Inconel 718?
Only when strength is not critical For load-bearing or high-stress components Inconel 718 is usually required.
Which Alloy is More Expensive?
Inconel 718 is typically more expensive due to its higher strength and more complex processing.
