Balancing Austenitic and Ferritic Phases
Posted: Sun Jan 19, 2025 6:00 am
For example, molybdenum increases strength and resistance to localised pitting, such as pitting or cracking. The amount of molybdenum found in duplex stainless steels typically varies from grade to grade by 2-5%. This is particularly important in marine and chemical processing applications where there is a high risk of chloride-induced corrosion. Studies have shown that a one percent increase in molybdenum content increases PREN (pitting resistance equivalent), a common measure used to assess an alloy’s resistance to extreme conditions.
Nitrogen strengthens while facilitating further pitting and crevice corrosion. It not only counteracts chromium depletion at the typical duplex SS level (0.1-0.3%), but also stabilizes austenite, thereby balancing the ferritic-austenite phase balance of the microstructure. For example, this balance can be used to create understanding homeowner database: everything you need to know mechanical properties such as tensile strength and hardness, making nitrogen- alloyed duplex stainless steels suitable for harsh environments such as desalination plants and offshore platforms.
If nitrogen levels are properly adjusted along with molybdenum and chlorine levels, the best corrosion resistance, high impact resistance values and a favorable price range can be achieved in a variety of applications under challenging circumstances.
In this regard, it is important to balance the austenitic and ferritic phases in duplex stainless steels to create the right microstructure that will perform better in harsh environmental conditions. The ideal microstructure contains about 50% ferrite and 50% austenite, but small deviations from this ratio can be tolerated, depending on the alloy composition and application. This control is possible by precisely manipulating alloying elements such as nitrogen, molybdenum, chromium and nickel during the manufacturing processes.
The chromium content mainly ranges between 18-30% and acts as a ferrite stabilizer, which contributes significantly to the high corrosion resistance of duplex stainless steels. Stabilization of the austenitic phase is achieved by adding nickel, the level of which varies between 4-8%, thus ensuring the preservation of a favorable two-phase structure. The addition of molybdenum (2-6%) increases the resistance to pitting/crevice corrosion, especially in chloride-rich environments. Nitrogen is usually present at around 0.3%, increases the yield strength of the steel and increases its susceptibility to localized corrosion; in addition, it also promotes the formation of stable austenite.
Nitrogen strengthens while facilitating further pitting and crevice corrosion. It not only counteracts chromium depletion at the typical duplex SS level (0.1-0.3%), but also stabilizes austenite, thereby balancing the ferritic-austenite phase balance of the microstructure. For example, this balance can be used to create understanding homeowner database: everything you need to know mechanical properties such as tensile strength and hardness, making nitrogen- alloyed duplex stainless steels suitable for harsh environments such as desalination plants and offshore platforms.
If nitrogen levels are properly adjusted along with molybdenum and chlorine levels, the best corrosion resistance, high impact resistance values and a favorable price range can be achieved in a variety of applications under challenging circumstances.
In this regard, it is important to balance the austenitic and ferritic phases in duplex stainless steels to create the right microstructure that will perform better in harsh environmental conditions. The ideal microstructure contains about 50% ferrite and 50% austenite, but small deviations from this ratio can be tolerated, depending on the alloy composition and application. This control is possible by precisely manipulating alloying elements such as nitrogen, molybdenum, chromium and nickel during the manufacturing processes.
The chromium content mainly ranges between 18-30% and acts as a ferrite stabilizer, which contributes significantly to the high corrosion resistance of duplex stainless steels. Stabilization of the austenitic phase is achieved by adding nickel, the level of which varies between 4-8%, thus ensuring the preservation of a favorable two-phase structure. The addition of molybdenum (2-6%) increases the resistance to pitting/crevice corrosion, especially in chloride-rich environments. Nitrogen is usually present at around 0.3%, increases the yield strength of the steel and increases its susceptibility to localized corrosion; in addition, it also promotes the formation of stable austenite.