Phase stability study on wrought duplex and super duplex stainless steels grade 4A, 5A and 6A at elevated temperatures and the effect on their mechanical properties

Duplex stainless steels with varying chromium content is taken and subject to heat treatment between the temperature ranges of 900 to 1000°C to understand the phase stability of ferrite at such elevated temperatures. It is well observed that, ferrite is the active phase in duplex stainless steel as the austenite grains remains unchanged after heat treatment. Also, formation of sigma in ferrite phases affects the toughness of the material, even though austenite is present in large amount. It is also observed that, higher the aging temperature, higher is the kinetics of formation sigma phase in duplex stainless steel. In addition to Cr, Mo increases the affinity of formation of sigma phase.Duplex stainless steels with varying chromium content is taken and subject to heat treatment between the temperature ranges of 900 to 1000°C to understand the phase stability of ferrite at such elevated temperatures. It is well observed that, ferrite is the active phase in duplex stainless steel as the austenite grains remains unchanged after heat treatment. Also, formation of sigma in ferrite phases affects the toughness of the material, even though austenite is present in large amount. It is also observed that, higher the aging temperature, higher is the kinetics of formation sigma phase in duplex stainless steel. In addition to Cr, Mo increases the affinity of formation of sigma phase.