Research Publications
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Item Homogenization of P91 weldments using varying normalizing and tempering treatment(2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.Creep strength enhanced ferritic/martensitic P91 steel is considered as a candidate material for the reactor pressure vessels and reactor internals of Very High Temperature Reactor (VHTR). Heterogeneous microstructure formation across the P91 weldments lead to premature Type IV cracking and makes the weldability of P91 steel a serious issue. The present research work describes the effect of normalizing and tempering (N&T) treatment on microstructure evolution in various zones of gas tungsten arc welded (GTAW) P91 pipe weldments. For N&T treatment, P91 pipe weldments were subjected to various normalizing (950�1150 �C) and tempering (730�800 �C) temperature. The effect of varying heat treatment on tensile properties and hardness of P91 pipe weldments were studied for V-groove and narrow-groove weld designs. The effect of increase in normalizing temperature (fixed tempering temperature) resulted in increase in strength and hardness, while increase in tempering temperature (fixed normalizing temperature) resulted in the decrease in strength and hardness of P91 steel weldments. The better combination of strength, ductility and microstructure were obtained for the maximum normalizing temperature of 1050 �C and tempering temperature of 760 �C. � 2017 Elsevier B.V.Item Some studies on P91 steel and their weldments(2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.In present research article, microstructure evolution in P91 steel and their weldments are reviewed in as-virgin and heat treatment and creep exposure condition. The thermal stability of P91 steel is derived from solid solution strengthening, sub-grain hardening and precipitation hardening. The initial microstructure plays an important role in deciding the mechanical properties of P91 steel and their weldment in long-term ageing and creep exposure condition. Effects of various alloying elements present in P91 steel and their related phase have also been discussed in details. The role of grain coarsening, Cr/Fe ratio, lath widening and dislocation density on creep rupture life of base metal and weldments are discussed. The combined effects of lath martensitic microstructure, residual stress and diffusible hydrogen content on performance of P91 steel material are also discussed. � 2018 Elsevier B.V.Item Characterization and evaluation of mechanical properties of CSEF P92 steel for varying normalizing temperature(2017) Saini N.; Pandey C.; Mahapatra M.M.The microstructural and mechanical properties of creep enhanced ferritic (CSEF) steels are affected by various parameters, solutionizing temperature is one of them. In the present investigation, the effect of normalizing temperature on the microstructural and mechanical properties of cast and forged (C&F) P92 steel were carried out. Grade P92 steel is considered as a candidate material for Thermal and Nuclear power plants at temperatures of up to 650��C. In this study, C&F P92 steel was subjected to various normalizing temperatures (from 950��C to 1150��C). For microscopic characterization, Optical microscope and Field emission scanning electron microscope (SEM) were used. The grain size, precipitate size, area fraction of precipitates and Cr/Fe were calculated from micrographs. The normalized specimens were tested for tensile strength, hardness, and toughness. Considering observation for the optimum combination of strength, ductility, and toughness, the normalizing at 1000��C and tempering at 760��C has been suggested for C&F P92 steel. � 2017 Elsevier B.V.Item Characterization of Cast and Forged (C&F) Gr. 91 Steel in Different Heat Treatment Condition(2017) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.The present research work deals with the results of influence of different heat treatment conditions on the microstructure stability and mechanical properties of high-chromium X10CrMoVNNB9-1(P91) cast and forged (C&F) P91 steel. The C&F P91 steel was subjected to various tempering condition in the temperature range of 350�760 �C and tempering time of 2 h, after the normalizing at 1040 �C for 40 min. The steel was also subjected to furnace cooled and water quenched heat treatment. Tempering at 650 and 760 �C produced the fully tempered lath martensitic structure with M23C6, M7C3, M3C and MX precipitates along the prior austenite grain boundaries, lath boundaries and matrix region. Tempering at 350 and 1000 �C produced the partially tempered columnar laths and untempered columnar laths martensite, respectively. The tempering time was also varied from 2 to 8 h for fixed tempering temperature of 760 �C. The optimum microstructure evolution was obtained for 6 h of tempering at 760 �C that led to improved mechanical properties. � 2017 The Indian Institute of Metals - IIM