Study on effect of double austenitization treatment on fracture morphology tensile tested nuclear grade P92 steel

Effect of 'conventional normalizing and tempering' (CNT) and 'double austenitization based normalizing and tempering' (DNT) process on microstructure characteristic and mechanical behavior was studied forP92 steel. In CNT heat treatment, P92 steel is normalized at 1040 degrees C/air cool and tempered with 760 degrees C/2 h/air cool. In DNT heat treatment, initially normalizing was performed at 1040 degrees C for 1 h followed by water quenching. After that sample was normalized in the temperature range of 950-1150 degrees C for 1 h and tempered at 760 degrees C/2 h/air cool (950 degrees C-DNT1, 1050 degrees C-DNT2, 1150 degrees C-DNT3).Grain size for CNT and DNT1 treatment were measured 17 +/- 7 mu m and 12 +/- 5 mu m. A DNT treatment resulted in homogeneous microstructure formation that led to improved mechanical properties as compared to CNT treatment. The DN based heat treatment produced complete martensitic microstructure formation by complete dissolution of carbide precipitates. The optimized room temperature condition was obtained for the DNT 1 heat treatment.