In the realm of superalloys, Inconel 625 and Inconel 718 stand tall, offering impressive strength and technical performance. These alloys are indispensable in advanced industrial applications, particularly in the aerospace, automotive, and oil and gas sectors. However, understanding the fundamental differences between Inconel 625 and Inconel 718 is essential when deciding which superalloy is best suited to a specific manufacturing process.
An Overview of Inconel 625 and Inconel 718
Inconel 625 and Inconel 718 belong to the Inconel alloy family, a group of superalloys primarily composed of nickel and known for their high strength, excellent heat resistance, and superb corrosion resistance.
Inconel 625
Inconel 625, comprised mostly of nickel and chromium, is recognized for its high tensile strength and excellent corrosion resistance, including its resistance to crevice corrosion. It retains strength in environments with very high or cryogenic temperatures, making it a popular choice for various aerospace applications and industries.
Inconel 718
Inconel 718 shares a similar chemical composition with Inconel 625, with slight variations. Known for its ability to be precipitation hardened without succumbing to post-weld cracking, Inconel 718 can resist creep rupture at temperatures up to 1,300°F. It is recognized for its high formability, making it comparable to general stainless steel grades.
Historical Development
The development of superalloys traces back to the 1950s and 1960s when researchers combined molybdenum and niobium with nickel to produce exceptionally strong alloys.
Inconel 625
Inconel 625 was first developed to cater to the need for strong steam-line piping products in steam power plants. The research was disrupted when it led to the discovery of another superalloy, Inconel 718. However, Inconel 625 quickly found its niche in aerospace applications and additional industries.
Inconel 718
Inconel 718, discovered incidentally during the development of Inconel 625, was immediately useful for applications in the aerospace industry, specifically airplane engines. Inconel 718 quickly found approval in 1962.
Chemical Composition
While Inconel 625 and Inconel 718 share many properties, they also have discernible distinctions that account for unique use cases.
Inconel 625
Inconel 625 is composed mainly of nickel and chromium. It also includes molybdenum and niobium, which contribute to its high tensile strength and robust corrosion resistance. It maintains its strength in environments up to 2,000° F, providing good oxidation resistance and resistance to carburization.
Inconel 718
Inconel 718 generally has a similar chemical composition to Inconel 625, with minor variations. It is notable for its capacity to be precipitation hardened without succumbing to post-weld cracking. It can also resist creep rupture at temperatures up to 1,300° F.
Formability Differences
Both Inconel 625 and Inconel 718 have high levels of formability due to the high concentration of nickel in the alloys. Both can be stamped and cold-formed. However, they have distinct formability characteristics due to their unique properties.
Inconel 625
Inconel 625, in an annealed condition, can be significantly stronger and particularly suited to resisting corrosion, including that caused by seawater environments.
Inconel 718
Inconel 718’s resistance to post-weld, or strain-age cracking during heat treatment makes it particularly suited to formability while maintaining high strength in an annealed condition.
Common Uses
Inconel 625 and Inconel 718 are used for various manufacturing applications. Product forms include strip, ribbon, and shaped wire, as well as round, flat, and square wire.
Inconel 625
Inconel 625 is particularly used for flexible metal hoses, heat exchangers, header bars, and marine components due to its significant strength in environments of elevated temperatures and corrosion, as well as its oxidation resistance.
Inconel 718
Inconel 718 has become more widespread in the aerospace industry. According to one study, the alloy makes up more than 30 percent of a modern aircraft engine’s finished component mass.
Industries That Commonly Use Inconel 625 and Inconel 718
While Inconel 625 and Inconel 718 are used in various industries, they have established a strong presence in specific sectors due to their unique properties.
Inconel 625
Inconel 625, due to its corrosion resistance, especially in sea salt environments, is widely used in the marine industry. This includes oil and gas industry needs, such as downhole drilling applications like tieback on undersea lines.
Inconel 718
Inconel 718 has made significant strides in the aerospace industry. It is also beneficial for components of automobile engines due to its high formability provided by the nickel content.
Conclusion
Understanding the differences between these superalloys is crucial for engineers and manufacturers. Both Inconel 625 and Inconel 718 offer a unique set of properties and uses, making them invaluable in various industrial applications.
Inconel 625 vs Inconel 718: At a Glance
| Property | Inconel 625 | Inconel 718 |
| Chemical Composition | Nickel and Chromium | Similar to Inconel 625 with minor variations |
| Resistance | High temperature, corrosion, and crevice corrosion | High temperature, post-weld cracking |
| Formability | High formability, especially in annealed condition | High formability, especially in annealed condition |
| Common Uses | Flexible metal hoses, heat exchangers, marine components | Aerospace industry, automobile engines |
| Industries | Marine, Oil, and Gas | Aerospace, Automotive |
By considering the unique properties and applications of each superalloy, you can determine which one best suits your manufacturing needs.
