Whether you are a supplier or an end user of Inconel alloys, choosing between Inconel 625 and Incoloy 825, or advising customers on material selection, can be challenging.
The application ranges of Inconel 625 and Incoloy 825 are quite similar. Since the Incoloy series was developed to reduce the cost of superalloys, Incoloy 825 can be considered a lower-cost alternative to Inconel 625.
In this article, we will compare the performance differences between these two alloys from various perspectives.
INCONEL® nickel-chromium alloy 625 (UNS N06625 / W.Nr. 2.4856) is used for its high strength, excellent fabricability (including joining), and outstanding corrosion resistance. Service temperatures range from cryogenic to 1800°F (982°C).
What is Incoloy Alloy 825?
INCOLOY® alloy 825 (UNS N08825 / W.Nr. 2.4858) is a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. The alloy’s chemical composition is designed to provide exceptional resistance to many corrosive environments.
The nickel content is sufficient for resistance to chloride-ion stress-corrosion cracking. The nickel, in conjunction with the molybdenum and copper, also gives outstanding resistance to reducing environments such as those containing sulfuric and phosphoric acids.
The molybdenum also aids resistance to pitting and crevice corrosion. The alloy’s chromium content confers resistance to a variety of oxidizing substances such as nitric acid, nitrates and oxidizing salt. The titanium addition serves, with an appropriate heat treatment, to stabilize the alloy against sensitization to intergranular corrosion.
The resistance of INCOLOY alloy 825 to general and localized corrosion under diverse conditions gives the alloy broad usefulness. Applications include chemical processing, pollution control, oil and gas recovery, acid production, pickling operations, nuclear fuel reprocessing, and handling of radioactive wastes. Applications for alloy 825 are similar to those for INCOLOY alloy 020.
Inconel Alloy 625 vs Incoloy Alloy 825 Chemical Composition
Here’s a comparison table for the chemical composition of Inconel 625 and Incoloy 825:
Inconel Alloy 625 vs Incoloy Alloy 825 Corrosion Resistance
Alloy 825 contains more iron than Alloy 625. While this lowers the cost of alloy 825, it also decreases the proportion of corrosion-resistant elements.
Inconel 625 has a higher nickel content compared to Incoloy 825, giving it a superior base for corrosion resistance.
Additionally, Inconel 625 has a significantly higher molybdenum content than Incoloy 825, enhancing its resistance to reductive corrosion.
Inconel Alloy 625 vs Incoloy Alloy 825 Mechanical Behavior
Both Inconel 625 and Incoloy 825 are solid solution strengthened alloys. However, Inconel 625 includes niobium and tantalum, which provide a stronger solid solution strengthening effect compared to other elements, resulting in higher mechanical strength.
Additionally, molybdenum is a highly effective solid solution strengthening element. The higher molybdenum content in Inconel 625 further enhances its strengthening effect.
| Inconel 625 | Incoloy 825 | |
|---|---|---|
| Tensile Strenght (MPa) | 827 | 586 |
| Yield Strenght (MPa) | 414 | 241 |
Inconel Alloy 625 vs Incoloy Alloy 825 Physical Properties
| Inconel 625 | Incoloy 825 | |
|---|---|---|
| Density, g/cm³ | 8.44 | 8.14 |
| Density, lb/in.³ | 0.305 | 0.294 |
| Melting Range, °F | 2350-2460 | 2500-2550 |
| Melting Range, °C | 1290-1350 | 1370-1400 |
| Permeability at 200 oersted (15.9 kA/m) | 1.0006 | 1.005 |
| Curie Temperature, °F | <-320 | <-320 |
| Curie Temperature, °C | -196 | <-196 |
Inconel Alloy 625 vs Incoloy Alloy 825 Application
In terms of applications, Inconel 625 and Incoloy 825 share some similarities but also exhibit significant differences.
Both alloys are used in chemical processing equipment like heat exchangers, pumps, and valves. They are also found in petroleum refining equipment and other industrial components exposed to high temperatures and corrosive environments.
However, due to its higher melting point and superior stress-rupture strength at elevated temperatures, Inconel 625 is typically employed in more demanding applications such as gas turbines and nuclear reactors. In contrast, Incoloy 825 is often utilized in less demanding applications such as exhaust manifolds and general chemical processing equipment.
Inconel Alloy 625 vs Incoloy Alloy 825 Main Standards
Here’s a comparison table for the standards of Inconel alloy 625 and Incoloy alloy 825:
Inconel Alloy 625 vs Incoloy Alloy 825 Cost
Although the performance of Incoloy 825 is not as good as Inconel 625, it is cheaper.
Therefore, when selecting materials, if the performance of alloy 825 is sufficient, then it is recommended to use alloy 825 to reduce costs.
Conclusion
Incoloy 825 is a cost-effective alternative to Inconel 625, offering slightly lower purity, corrosion resistance, and mechanical properties. However, its lower price makes it a preferred choice for many applications.
We manufacture a wide range of nickel alloy products, including both Alloy 625 and Alloy 825. If you have any requirements, please feel free to send us an inquiry.
