Brief study on δ-ferrite characterization: A review

The superior thermo-physical properties and long-term creep strength of P91 and P92 steels make it the attractive material in power plant units for high-temperature operating components. The Weldability of such steel is a serious issue and it depends on the welding process and heat treatment employed before and after welding. With respect to varying temperature regimes of heat treatment procedure, the nature of strengthening and mechanical properties of P91 and P92 steel vary. The present work describes the effect of autogenous tungsten inert gas (TIG) process on soft δ-ferrite formation in weld fusion zone of P91/P92 welded joint. The effect of heat treatment on morphology of the ferrite patches was also studied. The formation of the soft δ-ferrite patches was attributed to the presence of ferrite stabilizer like W and Mo in base steel and heat input.