Inconel 718 and 825 alloys: What are the differences?
Inconel 718 is a high-strength nickel-chromium alloy that performs exceptionally well in high-temperature applications due to its precipitation-hardening properties, and possesses excellent tensile and yield strength. Alloy 825 (commonly known as Incoloy 825) is a nickel-iron-chromium alloy with outstanding corrosion resistance, particularly against strong acids such as sulfuric acid and phosphoric acid. The main difference between the two lies in their respective strengths: Alloy 718 is known for its high strength, while Alloy 825 is renowned for its superior corrosion resistance.
What is the difference between Inconel 718 and 750?
Compared to Inconel X-750, Inconel 718 contains more chromium. This makes Inconel 718's oxidation resistance superior to Inconel X-750. Furthermore, Alloy 718 contains molybdenum, while Alloy X-750 does not. The addition of molybdenum improves Inconel 718's resistance to reducing corrosion.
What are the Differences Between Inconel 718 and Incoloy 825?
Inconel 718 vs. Incoloy 825 ASTM Standards
| Product Forms | Inconel 718 ASTM Standards | Incoloy 825 ASTM Standards |
| Sheet, Plate | ASTM B670, ASTM B168 | ASTM B424 |
| Seamless Pipe, Tubes | ASTM B163, ASTM B167 | ASTM B163, ASTM B423 |
| Strip | ASTM B168 | – |
Inconel 718 vs. Incoloy 825 Chemical Composition
| Element | Inconel 718 (%) | Incoloy 825 (%) |
| Nickel (Ni) | 50-55 | 38-46 |
| Chromium (Cr) | 17-21 | 19.5-23.5 |
| Molybdenum (Mo) | 2.8-3.3 | 2.5-3.5 |
| Iron (Fe) | Balance | Balance |
| Titanium (Ti) | 0.65-1.15 | 0.6-1.2 |
| Copper (Cu) | – | 1.5-3.0 |
| Niobium (Nb) | 4.75-5.5 | – |
| Aluminum (Al) | 0.2-0.8 | – |
| Cobalt (Co) | 1.0 max | – |
| Manganese (Mn) | 0.35 max | 1.0 max |
| Silicon (Si) | 0.35 max | 0.5 max |
| Carbon (C) | 0.08 max | 0.05 max |
| Sulfur (S) | 0.015 max | 0.03 max |
Inconel 718's higher nickel and niobium content gives it excellent strength at high temperatures, while Incoloy 825's higher iron and copper content enhances its corrosion resistance in acidic environments. Differences in chromium and molybdenum content also affect their corrosion resistance in both oxidizing and reducing environments.
Inconel 718 vs. Incoloy 825 Corrosion Resistance
| Property | Inconel 718 | Incoloy 825 |
| Resistance to Oxidizing Acids | Excellent up to 1300°F (704°C) | Moderate, suitable up to 1000°F (538°C) |
| Resistance to Reducing Acids | Moderate, limited to mild acidic environments | Excellent in sulfuric, phosphoric, and nitric acids |
| Chloride Ion Stress-Corrosion | Very high resistance (1.5% chloride solutions) | Good, suitable for chloride-rich environments |
| Pitting and Crevice Corrosion | Moderate, limited in chloride solutions | High, especially in marine and acidic conditions |
Inconel 718 vs. Incoloy 825 Physical Properties
| Property | Inconel 718 | Incoloy 825 |
| Density (g/cm³) | 8.19 | 8.14 |
| Melting Point (°C) | 1290-1350 | 1370-1400 |
| Tensile Strength (MPa) | 965-1103 | 585-880 |
| Yield Strength (MPa) | 550 | 220-450 |
| Thermal Conductivity (W/m·K) | 11.4 | 10.1 |
Inconel 718 vs. Incoloy 825 Mechanical Properties
| Property | Inconel 718 | Incoloy 825 |
| Tensile Strength (MPa) | 965-1103 | 585-880 |
| Yield Strength (MPa) | 550 | 220-450 |
| Elongation (%) | 12-15 | 30-40 |
| Hardness (Rockwell C) | 30-40 | 20-30 |
Inconel 718 vs. Incoloy 825 Thermal Properties
| Property | Inconel 718 | Incoloy 825 |
| Thermal Conductivity (W/m·K) | 11.4 | 10.1 |
| Specific Heat (J/kg·K) | 435 | 460 |
| Melting Point (°C) | 1290-1350 | 1370-1400 |
| Coefficient of Thermal Expansion (µm/m·°C) | 13.0 | 14.1 |
Inconel 718 vs. Incoloy 825 Weldability and Fabrication
| Property | Inconel 718 | Incoloy 825 |
| Weldability | Excellent, minimal post-weld cracking | Good, requires proper heat treatment |
| Machinability | Moderate, harder to machine due to strength | Easier, more ductile and softer |
| Post-Weld Heat Treatment | Required for optimal properties | Often required to stabilize alloy |
| Fabrication Complexity | High, especially for complex parts | Lower, easier to form and fabricate |
Inconel 718 vs. Incoloy 825 Applications
| Industry | Inconel 718 | Incoloy 825 |
| Aerospace | Widely used in turbine engines and aerospace components due to its high strength and temperature resistance. | Rarely used due to lower high-temperature capabilities. |
| Chemical Processing | Limited use, primarily in high-temperature environments. | Ideal for handling corrosive acids and aggressive environments. |
| Oil & Gas | Suitable for high-pressure, high-temperature environments. | Used in pipelines, pollution control, and oil refinery applications. |
| Marine | Performs well in saltwater environments. | Preferred for marine applications requiring resistance to pitting and crevice corrosion. |
Why Choose Gnee as Your Nickel-Based Alloy Supplier
✅ Over 18 years of export experience, products sold to more than 80 countries
✅ Certified by ISO, SGS, and BV
✅ Global inventory of Inconel, Hastelloy, Incoloy, and Monel alloy tubing, plates, and bars
✅ Custom processing services available – including cutting, polishing, CNC machining, and packaging
✅ Fast delivery within 7-15 days, supported by global logistics partners
📦 Packaging and Shipping
All stainless steel products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Steel is a supplier of Inconel 718 alloy, offering a wide range of products including: seamless pipe (sizes: 4-219 mm; thickness: 0.5-20 mm); welded pipe (sizes: 5.0-1219.2 mm; thickness: 0.5-20 mm); plates (thickness: 0.1 to 100 mm; width: 10-2500 mm); strips; alloy round bars (diameter: 3-800 mm); flat bars (thickness: 2-100 mm; width: 10-500 mm); hexagonal bars (size: 2-100 mm); wire rods; and extruded profiles. We collaborate with steel mills to provide our customers with Inconel 718 alloy products that meet or exceed numerous leading industry standards, including ASTM, ASME, SAE, AMS, ISO, DIN, EN, and BS standards.
Gnee Steel stocks and sells Inconel 718, pipes, plates, strips, round bars, flat bars, forged billets, hexagonal steel, wire rods, and extruded profiles. Please feel free to contact us at ss@gneesteel.com for a quote.
