Inconel 625 vs Inconel 718: Complete Selection Guide for Engineers
The Ultimate Engineer’s Selection Guide — chemical composition, mechanical properties, temperature performance, cost comparison, and industry applications. Choose the right nickel alloy for your project.
🔑 Key Differences at a Glance
| Property | Inconel 625 | Inconel 718 | 🏆 Winner |
|---|---|---|---|
| Chemical Base | Ni-Cr-Mo-Nb | Ni-Cr-Fe-Nb+Ti+Al | — |
| Tensile Strength | 827-1034 MPa | 1275-1379 MPa | ✅ 718 |
| Yield Strength | 414-655 MPa | 1034-1165 MPa | ✅ 718 |
| Max Temp (Oxidizing) | 980°C / 1800°F | 700°C / 1300°F | ✅ 625 |
| Corrosion Resistance | Excellent (seawater, acids) | Moderate | ✅ 625 |
| Weldability | Excellent | Good (sensitive to cracking) | ✅ 625 |
| Cost per kg | $$ (Moderate) | $$$ (Higher) | ✅ 625 |
| Age Hardenable | ❌ No | ✅ Yes | ✅ 718 |
| Best Use Case | Corrosive + High Heat | High Strength + Moderate Heat | Depends |
✔ Your application involves seawater, acids, or chlorides (chemical processing, marine, flue gas)
✔ Operating temperature exceeds 700°C
✔ You need excellent weldability without post-weld cracking concerns
✔ Budget is a consideration — 625 is typically 20-30% less expensive
✔ You need maximum mechanical strength at moderate temperatures
✔ Operating temperature is below 700°C
✔ Application is in aerospace engines, gas turbines, or fasteners
✔ You can leverage precipitation hardening for 1000+ MPa yield strength
🧪 Key Feature Comparison
Chemical Composition
625: Ni 58%+, Cr 20-23%, Mo 8-10%, Nb 3.15-4.15%
718: Ni 50-55%, Cr 17-21%, Fe bal., Nb+Ta 4.75-5.5%, Ti 0.65-1.15%
Mechanical Properties
625: Yield 414-655 MPa, Tensile 827-1034 MPa
718: Yield 1034-1165 MPa, Tensile 1275-1379 MPa (age-hardened)
Temperature Range
625: −196°C to 980°C
Excellent oxidation to 980°C
718: −253°C to 700°C
Strength drops rapidly above 650°C
📊 Detailed Technical Comparison
| Specification | Inconel 625 (UNS N06625) | Inconel 718 (UNS N07718) |
|---|---|---|
| ASTM Standards | B443, B444, B446, B704 | B637, B670, AMS 5662 |
| Density | 8.44 g/cm³ | 8.19 g/cm³ |
| Melting Range | 1290-1350°C | 1260-1336°C |
| Thermal Conductivity | 9.8 W/m·K @ 20°C | 11.4 W/m·K @ 20°C |
| Elastic Modulus | 207 GPa | 205 GPa |
| Hardness (HB) | 170-210 (annealed) | 330-400 (age-hardened) |
| Elongation | 30-45% | 12-20% (age-hardened) |
| Creep Resistance | Good up to 870°C | Excellent up to 650°C |
| Magnetic | Non-magnetic | Non-magnetic |
| Available Forms | Sheet/Plate/Bar/Pipe/Tube/Wire/Forging | Sheet/Plate/Bar/Forging/Fastener |
🏭 Industry Applications
Aerospace
625: Engine thrust reversers, exhaust ducts
718: Turbine discs, blades, fasteners, cryogenic tanks
Chemical Processing
625: Reactors, heat exchangers, acid piping
718: Pumps, valves, wellhead components
Oil & Gas
625: Sour gas tubing, subsea equipment
718: Downhole tools, drill collars, safety valves
Marine
625: Seawater piping, propeller blades
718: Shaft seals, fasteners in wet areas
Power Generation
625: SOFC interconnects, waste incineration
718: Gas turbine hot sections
Nuclear
625: Reactor core components
718: Control rod mechanisms
💰 Cost & Availability Comparison
Pricing varies significantly by product form, quantity, and market conditions. As of 2025:
- Inconel 625 Sheet/Plate: $45-75/kg
- Inconel 718 Sheet/Plate: $55-95/kg (precipitation hardening adds cost)
- Inconel 625 Pipe/Tube: $55-120/kg
- Inconel 718 Bar/Forging: $60-110/kg (aerospace demand drives pricing)
📦 Available Product Forms at Huaxiao Alloy
Sheets & Plates
Thickness: 0.3-100mm
Width: up to 2500mm
ASTM B443 / AMS 5599
Bars & Rods
Diameter: 6-500mm
Hot Rolled / Cold Drawn
ASTM B446 / AMS 5666
Pipes & Tubes
OD: 6-630mm, WT: 0.5-50mm
Seamless & Welded
ASTM B444 / B704
Forgings & Fittings
Flanges / Elbows / Tees
Custom forging available
ASTM B564 / B366
Wire & Welding
Wire: 0.1-12mm
ERNiCrMo-3 filler wire
Welding rod available
Custom Fabrication
CNC machining available
Laser/Plasma/Waterjet
MOQ: 1 piece
❓ Frequently Asked Questions
Q1: Can Inconel 625 and 718 be used interchangeably?
Not in most cases. 625 is best for high-temperature corrosive environments (chemical, marine). 718 is best for high-strength applications at moderate temperatures (aerospace, fasteners). Only in limited scenarios (moderate temp + moderate corrosion) can they be interchangeable — always consult an engineer.
Q2: Which alloy has better corrosion resistance?
Inconel 625 has significantly better corrosion resistance due to its high molybdenum (8-10%) and niobium content. It excels in seawater, HCl, H₂SO₄, and chloride environments. 718 has moderate corrosion resistance.
Q3: Which is more expensive — 625 or 718?
Inconel 718 is typically 20-35% more expensive than 625 due to precipitation hardening heat treatment, complex manufacturing, and higher aerospace demand. Request a quote for your specific quantity and form.
Q4: What are the available delivery conditions?
Inconel 625: Annealed or Solution Treated. Inconel 718: Solution Annealed, Age Hardened (AMS 5662/5663). Huaxiao Alloy delivers in your specified condition with mill test certificates.
Q5: What certifications do you provide?
Every shipment includes Mill Test Certificate (EN 10204 3.1). Third-party inspection (SGS, BV, TÜV) upon request. ASTM/AMS/ASME/NACE compliance. Additional testing (UT, PT, PMI) available.
Q6: What is your minimum order quantity?
Very flexible — plate from 1 sheet, pipe from 1 meter, bar from 1 piece. For custom dimensions, please contact us to check stock availability.
Need Inconel 625 or 718? We Have Stock.
Huaxiao Alloy stocks a full range of Inconel 625 and 718 products with fast global shipping, competitive pricing, and full mill certifications. Quote within 24 hours.
