Browsing by Author "Sirohi S."

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Effect of post weld heat treatments on microstructure evolution and type IV cracking behavior of the P91 steel welds joint
(2019) Pandey C.; Mahapatra M.M.; Kumar P.; Kumar S.; Sirohi S.
The creep tests were conducted on multi-pass shielded metal arc welded P91 steel weld joint at creep exposure temperature of 620 �C for an applied stress of 150 and 200 MPa in as-welded, and post weld heat treatments (PWHTs) state. The PWHTs involved the tempering at 760 �C/2 h/air cooling (referred as PWHT) and re-austenitizing at 1040 �C/60 min/air cooling + tempering at 760 �C/2 h/air cooling (refereed as PWNT). Results indicate a great influence of heat treatment conditions on the creep rupture life, fracture location and microstructure evolution of the P91 welded joint. As-welded and PWHT specimens showed the Type IV mode of failure and the fracture occurred in soft fine-grained heat affected zone/inter-critical heat affected zone (FGHAZ/IC-HAZ). In PWNT specimens, a shift in fracture location was observed from FGHAZ/ICHAZ to over tempered base zone. The degree of heterogeneity in terms of the microstructure and mechanical properties across the welded joints before the creep exposure have observed a great influence on the creep rupture life. As compared to other heat treated specimen, PWNT specimen exhibited higher creep rupture life at the lower applied stress of 150 MPa and creep exposure temperature of 620 �C due to lower degree of heterogeneity across the welded joints. However, Laves phase formation (Fe2W/Fe2Mo) was noticed in different zones (weld zone + heat affected zones) of the crept specimen for PWNT condition exposed at 620 �C for 150 MPa. � 2018 Elsevier B.V.
Fracture behaviour of crept P91 welded sample for different post weld heat treatments condition
(2019) Pandey C.; Mahapatra M.M.; Kumar P.; Sirohi S.
In the present research work, P91 steel plates of thickness 18 mm were welded using the shielded metal arc welding process. The welded steel plate subjected to different heat treatment condition including post weld heat treatment (760 �C for 2 h, followed by air cooling) and re-austenitizing (1040 �C for 60 min and air cooled) and tempered (760 �C for 2 h, followed by air cooling). The heat treatments were referred as the PWHT and PWNT. The creep sample was prepared to form the welded and heat treated plate. The creep tests were performed at 620 �C for stresses of 150 and 200 MPa. The weld fusion zone and fine-grained heat affected zone of the crept sample were characterized using the field emission scanning electron microscope (FESEM). The fracture surface morphology of crept sample was also studied using the FESEM. The maximum creep exposure time was measured for the PWNT sample as a result of homogeneous microstructure across the weldments. � 2018
Role of Heat Treatment on Grain Refinement and Microhardness of 9Cr�1Mo�V�Nb Steel
(2019) Pandey C.; Sirohi S.; Mahapatra M.M.; Kumar P.; Bansal K.K.
Effect of �double austenitizing� (DN) on microstructure evolution and mechanical properties of martensitic 9Cr�1Mo�V�Nb (P91) steel were studied and compared with the �conventional normalizing� (CN) process. In CN treatment, P91 steel is normalized at 1050��C for 1�h, finally air cooled. In DN treatment, the first stage of normalizing was performed at 1050��C/1�h/air cool. The second stage of normalizing was performed in the temperature range of 950�1150��C for 1�h (950��C-DN1, 1050��C-DN2, 1150��C-DN3), followed by water quenching. The grain size was measured 42 and 35��m for CN and DN1 treatment, respectively. The double normalizing (DN) produced complete martensitic microstructure as a result of complete dissolution of precipitates. In DN-based heat treatment, optimized microstructure and mechanical properties were obtained for the sample that normalized at 950��C, followed by water quenching. � 2019, ASM International.