Whether you are a supplier or a end user of Inconel alloys, you may face challenges when deciding between Inconel 600 and Inconel 625 alloy or advising customers on material selection.
Inconel alloy 600 and Inconel 625 alloy are solid solution strengthened Inconel alloys.
Due to some chemical contents differences, these two alloys have different corrosion resistance and strength.
This article will compare these alloys from various aspects to better enable you to make the right choice in the coming project.
INCONEL® (nickel-chromium-iron) alloy 600 (UNS N06600 / W.Nr. 2.4816) is a standard engineering material for applications which require resistance to corrosion and heat. The alloy also has excellent mechanical properties and presents the desirable combination of high strength and good workability.
What is Inconel Alloy 625?
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).
Inconel Alloy 600 vs Inconel Alloy 625 Chemical Composition
Here’s a comparison table for the chemical composition of Inconel 600 and Inconel 625:
Inconel Alloy 600 vs Inconel Alloy 625 Corrosion Resistance
In nickel alloys, nickel itself provides excellent corrosion resistance, making both Inconel 600 and Inconel 625 highly effective in corrosive environments.
Inconel 625 has a higher chromium content than Inconel 600, enhancing its oxidation resistance. As a result, Inconel 625 offers superior antioxidant properties compared to Inconel 600.
Additionally, Inconel 600 lacks molybdenum, while Inconel 625 contains over 8% molybdenum, giving it resistance to reducing environments—a feature absent in Inconel 600.
Thus, Inconel 625 exhibits significantly better overall corrosion resistance than Inconel 600.
Inconel Alloy 600 vs Inconel Alloy 625 Mechanical Behavior
Due to its large atomic radius, molybdenum serves as an excellent solid solution strengthening element.
As mentioned earlier, the presence of molybdenum in alloy 625 enables it to resist reduction. Additionally, after solid solution treatment, molybdenum significantly enhances the alloy’s strength.
Similarly, niobium and tantalum, with their large atomic radii, act as effective solid solution strengthening elements in alloy 625, improving its mechanical properties.
During heat treatment, niobium and tantalum contribute to the formation of γ” precipitation strengthening phases, further boosting the strength of alloy 625.
Although Inconel 625 is primarily a solid solution strengthened alloy (initially designed with aluminum and titanium for refinement), it still undergoes precipitation strengthening with γ’ phases, further enhancing its performance.
When the chromium content ranges from 20% to 25%, a short-range ordered strengthening mechanism occurs, precisely within the design range of alloy 625, thereby increasing its strength.
In nickel-based superalloys, cobalt reduces the stacking fault energy of the alloy, thereby enhancing its overall strength.
Inconel Alloy 600 vs Inconel Alloy 625 Physical Properties
| Inconel 600 | Inconel 625 | |
|---|---|---|
| Density, g/cm³ | 8.47 | 8.44 |
| Density, lb/in.³ | 0.306 | 0.305 |
| Melting Range, °F | 2470-2575 | 2350-2460 |
| Melting Range, °C | 1354-1413 | 1290-1350 |
| Permeability at 200 oersted (15.9 kA/m) | 1.010 | 1.0006 |
| Curie Temperature, °F | -192 | <-320 |
| Curie Temperature, °C | -124 | -196 |
Inconel Alloy 600 vs Inconel Alloy 625 Application
The Inconel 600 alloy is used extensively in the chemical industry for its strength and corrosion resistance. Applications include heaters, stills, bubble towers and condensers for processing of fatty acids; evaporator tubes, tube sheets and flaking trays for the manufacture of sodium sulfide; and equipment for handling abietic acid in the manufacture of paper pulp.
Due to its excellent corrosion resistance, a typical application of Inconel 625 is marine. Its resistance to localized corrosion (pitting and crevice corrosion), chloride ion stress corrosion, and its excellent fatigue strength make it widely used in marine parts such as propeller blades, exhaust pipes, and fasteners. For ambient temperature applications, Inconel 625 is recommended to be delivered annealed.
In addition, Inconel 625 is also widely used in the aerospace field, thanks to its excellent high-temperature tensile properties and creep strength. Through processing and welding, Inconel 625 can be used in components such as aircraft piping systems, engine exhaust systems, fuel and hydraulic lines, and heat exchanger tubes. The high temperature properties of Inconel 625 alloy also make it used in heat treatment equipment and chemical industry.
Inconel Alloy 600 vs Inconel Alloy 625 Main Standards
Here’s a comparison table for the standards of Inconel alloy 600 and Inconel alloy 625:
Inconel Alloy 600 vs Inconel Alloy 625 Cost
Alloy 625 features a more intricate alloying composition, challenging processing requirements, and superior performance, resulting in a significantly higher price compared to Inconel 600.
If Inconel 600 meets all the requirements for your project, we recommend opting for this alloy initially to achieve cost savings.
Conclusion
Because of its higher chromium and molybdenum content, Inconel 625 offers superior overall corrosion resistance compared to Inconel 600.
Additionally, the synergy of various strengthening elements endows alloy 625 with superior mechanical properties relative to alloy 600.
The enhanced performance and more intricate composition of alloy 625 contribute to its higher cost, making the more economical alloy 600 preferable when feasible.
HZW manufactures cost-effective products using both Inconel 600 and Inconel 625. If you have specific requirements, please feel free to reach out to us.
