Prior-austenite grain refinement in P92 steel using double austenitization treatment

The experimental investigation of 'double austenitization based normalizing and tempering' (DNT) heat treatments on tensile behavior and microstructural morphology of the CSEF/M P92 steel was carried out and compared it with the 'conventional normalizing and tempering' (CNT) heat treatment. The CNT treatment was performed at the normalizing temperature of 1040 °C for 60 min, followed by air cooling and then tempered at 760 °C for 120 min, followed by the air cooling. The DNT treatment involved the initial austenitizing at the temperature 950, 1100 and 1150 °C for 60 min, followed by the water quenching for higher dislocation density and then further austenitized at 1040 °C for 60 min followed by the air cooling. After the double austenitization based normalizing, tempering was performed at 760 °C for 2 h. The double austenitized samples are named as DNT 1 (950 °C), DNT 2 (1100 °C) and DNT 3 (1150 °C). The fine grain structure was obtained for the DNT 3 treatment. The fracture surface morphology of tensile tested specimen was studied using the field emission scanning electron microscope (FESEM). The results of tensile tests were obtained superior for the DNT treatment as compared to CNT treatment. Microstructure also showed the refinement of the grain size and lath width after the DNT treatment. (paper)