With an increasing number of projects on sour services, Inconel grades 625 and 825 are frequently demanded by customers. Here is a short summary of what these grades are, and why are they in such high demand despite the high prices.
Inconel 625 and Inconel 825 are two alloys that are commonly used in a variety of high-temperature and corrosion-resistant applications. Both of these alloys are known for their excellent resistance to corrosion and high-temperature performance, but they have some key differences in their properties and performance characteristics.
Inconel 625 is a nickel-based alloy that is known for its excellent resistance to corrosion in a wide range of environments. It is especially resistant to corrosion in seawater, making it a popular choice for marine applications. Inconel 625 also has good resistance to stress corrosion cracking and pitting, and is resistant to a variety of chemicals, including organic acids and chlorides. It has a composition of approximately 58% nickel, 20% chromium, and 9% molybdenum, and has a melting point of around 2600°F (1427°C).
Inconel 825 is a nickel-iron-chromium alloy that is known for its excellent resistance to corrosion in both acidic and basic environments. It is also resistant to pitting, crevice corrosion, and stress corrosion cracking, and has good resistance to a variety of chemicals, including sulfuric acid, hydrochloric acid, and phosphoric acid. It has a composition of approximately 38% nickel, 22% chromium, and 46% iron, and has a melting point of around 2550°F (1399°C).
In terms of mechanical properties, Inconel 625 and Inconel 825 are similar in many ways. Both alloys have good tensile strength and elongation, and are known for their good fatigue resistance. However, Inconel 825 has slightly higher yield strength and tensile strength than Inconel 625, making it a better choice for applications that require higher strength.
Both Inconel 625 and Inconel 825 are excellent choices for use in sour gas and crude oil with high H2S content, due to their excellent corrosion resistance in these environments. Inconel 625 is often used in sour gas service due to its good resistance to stress corrosion cracking and pitting, while Inconel 825 is often used in crude oil service due to its good resistance to corrosion in acidic environments.