Nickel-based alloys are the backbone of high-reliability sectors such as energy, chemical processing, oil & gas, marine, aerospace, and nuclear industries. Among the most prescribed are Incoloy 825 and Inconel 625, two alloys engineered for outstanding service in aggressive corrosive and high-temperature conditions. Industrial professionals frequently face the challenges choosing between Incoloy 825 vs Inconel 625 which alloy is the optimal fit for project critical applications?
This expert guide by Kalpataru Piping Solutions delivers an in-depth comparison, presenting actionable insights based on advanced metallurgy, grade-specific mechanical properties, fabrication and welding challenges, detailed corrosion resistance types, and real-world use-cases.
What is Inconel 625?
Inconel 625 is a Ni-Cr-Mo-Nb solid solution strengthened superalloy (UNS N06625, W.Nr. 2.4856). Renowned for high strength, ductility, and superb corrosion and oxidation resistance from cryogenic to 982°C, it finds critical use in aerospace, marine, nuclear, power, and chemical plants, particularly at elevated temperatures.
Inconel 625 Chemical Composition
|
Element |
Content (% by weight) |
|
Nickel (Ni) |
58.0 min. |
|
Chromium |
20.0–23.0 |
|
Molybdenum |
8.0–10.0 |
|
Niobium + Ta |
3.15–4.15 |
|
Iron (Fe) |
≤5.0 |
|
Others |
Mn, Si, Al, Ti (trace) |
Key point: High Ni, Mo + Nb enhance strength and corrosion resistance, especially against pitting, crevice, and chloride stress cracking.
Inconel 625 Material Properties
|
Property |
Typical Value |
|
Density (g/cm³) |
8.44 |
|
Melting Point (°C) |
1290–1350 |
|
Tensile Strength (MPa) |
827–1276 |
|
Yield Strength (MPa) |
414–528 |
|
Elongation (%) |
30–54 |
|
Max. Use Temp. (°C) |
982 (short-term) |
|
Hardness (HB) |
100–180 |
What is Incoloy 825?
Incoloy 825 (UNS N08825, W.Nr. 2.4858) is a Ni-Fe-Cr alloy stabilized with molybdenum, copper, and titanium. Its design focus is robust resistance to strong acids, stress corrosion, and intergranular attack across nuclear, petrochemical, pollution control, and pickling environments.
Incoloy 825 Chemical Composition
|
Element |
Content (% by weight) |
|
Nickel |
38.0–46.0 |
|
Chromium |
19.5–23.5 |
|
Iron |
22.0 min. |
|
Molybdenum |
2.5–3.5 |
|
Copper |
1.5–3.0 |
|
Titanium |
0.6–1.2 |
|
Others |
Mn, Si, Al, C (trace) |
Incoloy 825 Material Properties
|
Property |
Typical Value |
|
Density (g/cm³) |
8.14 |
|
Melting Point (°C) |
1370–1400 |
|
Tensile Strength (MPa) |
586–690 |
|
Yield Strength (MPa) |
241–324 |
|
Elongation (%) |
30–45 |
|
Max. Use Temp. (°C) |
540 |
|
Hardness (HRB) |
~90 |
Inconel 625 vs Incoloy 825: Standard Comparison
Compare Inconel 625 and Incoloy 825 across corrosion resistance, temperature tolerance, mechanical strength, and fabrication. Understand which alloy suits your industrial needs for chemical, marine, and high-temperature applications.
| Product Form | Inconel 625 (ASTM/ASME) | Incoloy 825 (ASTM/ASME) |
| Seamless Pipe | B444, B829 | B423, B829 |
| Welded Pipe | B705, B751 | B705, B751 |
| Tube | B444, B704, B751 | B163, B704, B751 |
| Rod & Bar | B446 | B425 |
| Forging | B564 | B564 |
| Plate/Sheet | B443 | B424 |
| Fitting | B366 | B366 |
| Flange | B564 | B564 |
Corrosion Resistance — Inconel 625 vs Incoloy 825
Inconel 625 shows excellent resistance in seawater, brine, and chloride stress cracking, making it ideal for marine and oil & gas applications. It performs well in acids and hydrochloric environments, especially under severe or variable conditions. Incoloy 825, on the other hand, excels in sulfuric and phosphoric acids, making it suitable for acid storage and reactors, and performs reliably in hydrochloric acid at moderate temperatures. Both alloys offer excellent protection in mixed oxidizing and reducing environments.
Temperature Tolerance & Heat Treatment
Inconel 625 can withstand service temperatures up to 982°C (1800°F) and benefits from solution annealing, which enhances creep resistance. This makes it ideal for high-temperature applications such as turbines, exhaust systems, and hot marine piping. Incoloy 825, with a maximum service temperature of 540°C (1004°F), is supplied in an annealed condition that maintains excellent acid resistance, making it suitable for acid and chemical process piping where moderate temperatures are encountered.
Mechanical Strength & Durability
Inconel 625 offers superior mechanical properties, with a yield strength of 414–528 MPa, tensile strength of 827–1276 MPa, and elongation up to 54%. Its top-tier fatigue strength makes it ideal for dynamic loading applications such as risers, studs, and rods. Incoloy 825, with a yield strength of 241–324 MPa, tensile strength of 586–690 MPa, and elongation between 30–45%, provides moderate fatigue resistance and is best suited for static or low-cycle applications like tanks, sheets, and lining in chemical and industrial systems.
Fabrication & Machinability
Inconel 625 is challenging to machine due to work hardening but offers excellent weldability when carefully controlled. Post-weld treatment is recommended for service above 650°C, making it suitable for small components exposed to fatigue or high heat. Incoloy 825 is easier to machine, welds very well, and typically does not require post-weld treatment, making it ideal for large flanges, tanks, and pipelines in chemical and industrial applications.
Inconel 625 vs Incoloy 825: Price Comparison
Inconel 625 is generally more expensive due to its high nickel, molybdenum, and niobium content, along with strong global demand. Its forms, such as pipes, tubes, and flanges, carry a premium because of complex alloying and processing requirements. Incoloy 825, with lower nickel and higher iron content, is a more cost-effective option, especially for large-section fabrications like tanks and pipelines. Final pricing for both alloys depends on factors such as raw material composition, manufacturing processes, supply chain, order quantity, and any dimensional or customization requirements.
Incoloy 825 vs Inconel 625: Applications, Sector Guidance, and Product Fit
Explore the applications, sector suitability, and product fit of Incoloy 825 and Inconel 625. Learn which alloy excels in acids, seawater, or high-temperature operations and make informed material selection decisions.
| Sector | Application | Alloy Choice | Rationale | Product Form |
| Oil & Gas | Seawater risers, wellheads | Inconel 625 | Top pitting/SCC & fatigue | Pipe, flange, stud |
| Chemical | Acid storage, pickling tanks | Incoloy 825 | Acid resistance, cost | Plate, pipe, tank |
| Marine | Heat exchangers, seawater pipes | Inconel 625 | Seawater corrosion | Pipe, tube, U-bend |
| Nuclear | Fuel reprocessing, waste storage | Incoloy 825 | Acid+mixed phase durability | Rod, bar, tube |
| Energy | Turbine exhaust, hot ducting | Inconel 625 | Hot fatigue, creep | Rod, sheet, forged |
| Power (FGD) | Scrubber, gas duct | Incoloy 825 | Acid, mixed solution resist. | Sheet, plate, weld |
Summary Table – Which Alloy Suits Which Use
| Application Condition | Prefer Incoloy 825? | Prefer Inconel 625? | Why? |
| Acidic (phosphoric/sulfuric) | Yes | Sometimes (if high temp/SCC) | 825: best for most acids |
| Hot/cyclic (>650°C) | No | Yes | Only 625 withstands |
| Dynamic load, stress | Sometimes | Yes | 625 fatigue resistance |
| Seawater, brine, marine | Maybe (mild) | Yes | 625 excels in critical |
| Large static fabrication | Yes | Maybe | 825 is more economical |
| Tight tolerance machines | Yes | Maybe (tougher to work) | 825 fabricates more easily |
| Welded acid process tanks | Yes | No | 825: top weld corrosion |
Which Should You Choose – Incoloy 825 or Inconel 625?
| Requirement/Constraint | Recommended Alloy | Reason |
| Max acid/corrosion resistance | Incoloy 825 | Economic and reliable |
| Highest pitting/SCC defense | Inconel 625 | Handles extremes |
| Long life under vibration | Inconel 625 | Fatigue & creep resistance |
| Lower raw material & fab cost | Incoloy 825 | Lower Ni/Mo, easier to weld |
| Hot, high-stress duty | Inconel 625 | Only one with creep/fatigue |
| General static piping/tanks | Incoloy 825 | Sufficient/cost-saving |
For guaranteed supply of Inconel 625 and Incoloy 825 pipes, plates, rods, flanges, and custom fabrications, trust Kalpataru Piping as industry-certified, global supplier with full certification, prompt delivery, and end-to-end support.
Conclusion – Incoloy 825 vs Inconel 625
| Feature/Factor | Best With… | Notes |
| Composition & Cost | Incoloy 825 | Iron lowers cost, maintains acid resistance |
| Pitting/Fatigue | Inconel 625 | Ni, Mo, Nb = fatigue, SCC, marine, longevity |
| Weldability | Incoloy 825 | Simpler fabrication, less post-weld stress |
| Mechanical Strength | Inconel 625 | Dynamic/vibrating/max temp |
| Application Fit | See industry/app | Use tables above for sector-specific selection |
Kalpataru Piping provides high-quality Inconel 625 and Incoloy 825 products, including sheets, plates, rods, flanges, and pipes for industrial projects worldwide delivered with global certifications and deep technical support.
