Ultra Austenitic Stainless Steels
Ultra-austenitic stainless steels, also known as super austenitics and 904L, are high strength and high toughness stainless steels that show better corrosion resistance than conventional austenitic steels. Super austenitics typically contain at least 25% chromium and nickel, along with other alloying elements.
The primary benefit of super austenitics is their ability to resist pitting and crevice corrosion attacks in the presence of chlorides. This type of corrosion is especially common in industrial environments and chemical plants, and super austenitics offer a significant advantage over standard austenitic stainless steels. Additionally, they have very good strength and ductility, and are able to maintain their resistance to chloride induced corrosion even after being welded.
These stainless steels are typically used in chemical and petrochemical processing and other industrial applications that involve high levels of chloride contamination. The super austenitic grade is especially popular among those in the metal industry, since it is resistent to heat treatments that tend to cause other types of stainless steels to become brittle.
Super austenitic stainless steels contain higher amounts of chromium, nickel, and molybdenum than other austenitics. Additionally, most have a significant amount of nitrogen, which increases the corrosion resistance. Common grades include 904L, 254SMO and Duplex. 904L is the most common grade and is highly resistant to corrosion and stress corrosion cracking. 254SMO, on the other hand, contains high levels of both chromium and molybdenum, and is especially resistant to pitting and crevice corrosion. Finally, Duplex is a combination of austenitic and ferritic stainless steel, providing greater strength and toughness than either of those grades can offer on their own.
Though super austenitics are more expensive than other types of stainless steel, their higher levels of corrosion resistance and strength to weight ratio make them an excellent choice for many industrial applications. They offer better resistance to chlorides, as well as a higher tolerance to thermal cycling that allows them to be used in many different types of environments. Their improved strength, along with their better corrosion resistance and heat resistance, make them an ideal choice for applications that require high levels of strength and corrosion protection.
Overall, ultra-austenitic stainless steels are a great choice for many industrial applications. Due to their higher chromium, nickel, and molybdenum levels, they offer excellent corrosion resistance, especially in the presence of chlorides. Additionally, they are very strong and ductile, with a high tolerance to thermal cycling that makes them ideal for a wide variety of applications. Their higher cost notwithstanding, these special stainless steels are an excellent choice for any application that requires superior strength and corrosion resistance.
