Research Publications

Permanent URI for this collectionhttps://idr.iitbbs.ac.in/handle/2008/2

Browse

Author: search.filters.author.Saini N.End date: 2018

Search Results

Now showing 1 - 10 of 29
  • No Thumbnail Available
    Item
    Effect of strain rate and notch geometry on tensile properties and fracture mechanism of creep strength enhanced ferritic P91 steel
    (2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
    Creep strength enhanced ferritic (CSEF) P91 steel were subjected to room temperature tensile test for quasi-static (less than 10?1/s) strain rate by using the Instron Vertical Tensile Testing Machine. Effect of different type of notch geometry, notch depth and angle on mechanical properties were also considered for different strain rate. In quasi-static rates, the P91 steel showed a positive strain rate sensitivity. On the basis of tensile data, fracture toughness of P91 steel was also calculated numerically. For 1 mm notch depth (constant strain rate), notch strength and fracture toughness were found to be increased with increase in notch angle from 45� to 60� while the maximum value attained in U-type notch. Notch angle and notch depth has found a minute effect on P91 steel strength and fracture toughness. The fracture surface morphology was studied by field emission scanning electron microscopy (FESEM). � 2017 Elsevier B.V.
  • No Thumbnail Available
    Item
    Dissimilar joining of CFEF steels using autogenous tungsten-inert gas welding and gas tungsten arc welding and their effect on ?-ferrite evolution and mechanical properties
    (2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
    Ferritic/martensitic 9Cr-1Mo-V-Nb steel also designated as ASTM A335 used in construction of several components of power plants operating in temperature range of 600�650 �C. In present investigation, dissimilar weld joints of P91 and P92 steel were prepared using the autogenous tungsten inert gas welding (A-TIG) and multi-pass gas tungsten arc (GTA) welding process. A comparative was performed on evolution of ?-ferrite patches in weld fusion zone and heat affected zone (HAZ) of welded joints. The evolution of ?-ferrite patches was carried out in as-welded and post-weld heat treatment (PWHT) condition. PWHT was carried out at 760 �C for 2 h for both A-TIG and GTA welding process. For A-TIG weld joint higher yield strength, ultimate tensile strength (UTS) and peak hardness were measured due to higher heat input in single pass and higher carbon content in weld fusion zone. Higher heat input, fast cooling rate and higher weight percentage of ferrite stabilizer like vanadium (V) and niobium (Nb) in A-TIG weld joint were resulted in formation ferrite patches in weld fusion zone and heat affected zone. Higher weight percentage of V and Nb in A-TIG weld zone was resulted poor impact toughness of A-TIG weld fusion zone than GTA welds in as-welded condition. After the PWHT at 760 �C�2 h, Charpy toughness of A-TIG weld fusion zone (48 J) just meet the minimum required value as required by the EN: 1557:1997 (47 J). � 2017
  • No Thumbnail Available
    Item
    Effect of cooling medium on microstructure evolution and tensile properties of creep-strength-enhanced ferritic steel
    (2018) Pandey C.; Saini N.; Thakre J.G.; Mahapatra M.M.; Kumar P.
    In creep-strength-enhanced ferritic steels, hydrogen-induced cold cracking of weldments is a serious issue. In the present research work, the effect of cooling medium on tensile properties and microstructure evolution of P91 steel weldments has been studied. For water-cooling condition, the diffusible hydrogen metal in deposited metal was measured by the mercury method. The microstructure of weldments in different cooling condition was characterized by using the field-emission scanning electron microscope (FE-SEM) and optical microscope. The fractured tensile test samples were characterized using the FE-SEM. The maximum tensile strength was measured to be 624 MPa for air-cooling medium (very low level of diffusible hydrogen). � 2018 Sociedade Portuguesa de Materiais (SPM)
  • No Thumbnail Available
    Item
    Effect of welding process and PWHT on ?-ferrite evolution in dissimilar P91 and P92 steel joint
    (2018) Pandey C.; Mohan Mahapatra M.; Kumar P.; Mulik R.S.; Saini N.; Gopal Thakre J.
    Ferritic/martensitic 9Cr-1Mo-V-Nb (P91) and 9Cr-0.5Mo-1.8W-V-Nb (P92) steel are used for high temperature (600-650�C) operating components in nuclear and thermal power plants. The present research work deals with the dissimilar joining of P91 and P92 steel using autogenous tungsten inert gas (TIG) welding and multi-pass gas tungsten arc welding (GTAW) with filler. The evolution of ?-ferrite patches in weld fusion zone and heat affected zones (HAZs) were characterized in as-welded and post weld heat treatment (PWHT) condition. PWHT was carried out at 760�C for 2 h and 6 h, for both autogenous-TIG and GTA weld joints. Charpy toughness and microhardness tests were performed for autogenous-TIG welding and GTA welding process under as-welded and PWHT condition. � 2018 Elsevier Ltd.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Item
    Evolution of nano-size precipitates during tempering of 9Cr-1Mo-1W-V-Nb steel and their influence on mechanical properties
    (2018) Saini N.; Pandey C.; Mahapatra M.M.; Mulik R.S.
    The aim of the characterization of P911 steel is to determine the consequence of different tempering temperature on nano-size particle evolution and their effect on the mechanical properties. P911 steel was normalized at 1040 �C for 1 h and subjected to varying tempering condition in the range of 720�800 �C for 2 h of tempering time. To study the effect of tempering temperature on nano-size particles distribution and grain size of P911 steel, field-emission scanning electron microscope (FESEM) and optical microscope (OM) were utilized. The other tests were hardness measurement and room-temperature tensile testing was performed to characterize the P911 steel for different tempering condition. The ultimate tensile strength (UTS) and hardness have found a great dependency on the area fraction of precipitates present in the microstructure. The UTS and hardness were observed to be increased continuously with increase in tempering temperature in range of 720�800 �C. � 2017 Elsevier B.V.
  • No Thumbnail Available
    Item
    Comparative study of autogenous tungsten inert gas welding and tungsten arc welding with filler wire for dissimilar P91 and P92 steel weld joint
    (2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
    Creep strength enhanced ferritic/martensitic 9Cr-1Mo-V-Nb (P91) steel is also designated as ASTM A335 used for out-of-core and in-core (piping, cladding, ducts, wrappers, and pressure vessel) of Gen IV reactors. In present investigation, the dissimilar weld joint of P91 and P92 steel were made using the autogenous tungsten inert gas (TIG) welding with single pass, double side pass and multi-pass gas tungsten arc (GTA) welding with filler wire. Microstructure evolution in sub-zones and mechanical properties of dissimilar welded joints were studied in as-welded and post weld heat treatment (PWHT) condition. Formation of ?-ferrite patches in weld fusion zone and heat affected zones (HAZs) and their influence on the mechanical behaviour of the welded joints were also studied. Presence of higher content of ferrite stabilizer in P92 steel have resulted the formation of ?-ferrite patches in weld fusion zone as well as HAZs. The ?-ferrite was observed in autogenous TIG welds joints. The ?-ferrite patches were formed in as-welded condition and remained in the microstructure after the PWHT. The ?-ferrite patches leads to reduction in Charpy toughness of autogenous TIG welds joint and also lower down the average hardness of weld fusion zone. Peak hardness and poor impact toughness were observed for autogenous TIG welds joint as compared to GTA welds. For microstructure characterization, field-emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS) and optical microscope were utilized. � 2017 Elsevier B.V.
  • No Thumbnail Available
    Item
    Study on the effect of ageing on laves phase evolution and their effect on mechanical properties of P92 steel
    (2018) Saini N.; Mulik R.S.; Mahapatra M.M.
    P92 steel is candidate material for application in reactor pressure vessels in nuclear power plants. In present investigation, Laves phase evolution (at 650 �C) with varying ageing time (upto 3000 h) in P92 steel and their effect on mechanical properties have been investigated. During thermal ageing, the microstructure analysis showed the evolution of Laves phase that degrades the strength of P92 steel. The formation of Laves phase was observed after the thermal ageing of 720 h and it showed higher coarsening rate in ageing time range of 720 h ?1440 h. The Laves phase formation was also confirmed by the XRD analysis, and line mapping. The strength and ductility decreased as a result of deprivation of solid solution strengthening and formation of Laves phase. The hardness of P92 steel was also affected by ageing time but less pronounced as compared to strength. Charpy toughness was also reduced continuously with increase in ageing time as a result of thermal straining of particles and Laves phase formation. � 2018 Elsevier B.V.
  • No Thumbnail Available
    Item
    On study of effect of varying tempering temperature and notch geometry on fracture surface morphology of P911 (9Cr-1Mo-1W-V-Nb) steel
    (2018) Saini N.; Pandey C.; Mahapatra M.M.; Mulik R.S.
    Before putting in service, the creep strength enhanced ferritic (CSEF) steels are subjected to varying tempering treatment to produce a vast array of mechanical properties and to achieve the optimum combination of microstructure and mechanical properties by controlling normalizing and tempering temperature/time. In the present investigation, P911 steel was subjected to a fixed normalizing temperature of 1040 �C for 1 h and then, subjected to varying tempering temperature (720 �C�800 �C) for 2 h of tempering time. The effect of notch geometry on the tensile properties with respect to the varying tempering temperature was also investigated. The microstructural characterization was studied using optical microscope and field-emission scanning electron microscope (FESEM). A decrease in grain size, hardness and strength were noticed with increase in tempering temperature initially but after 740 �C, the grain size and strength were found to be increased continuously. The area fraction of precipitates was found to be varied inversely with the grain size. For a particular tempering temperature, an increase in notch depth resulted in increase in strength and decrease in ductility. The best combination of hardness, ductility and strength were achieved after normalized at 1040 �C for 1 h and tempered at 760 �C for 2 h. � 2017 Elsevier Ltd
  • No Thumbnail Available
    Item
    Autogenous tungsten inert gas and gas tungsten Arc with filler welding of dissimilar P91 and P92 steels
    (2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
    Creep strength ferritic/martensitic modified 9Cr-1Mo-V-Nb (P91) steel also designated as ASTM A335 and P92 steel are used for piping, cladding, ducts, wrappers, and the pressure vessel in Gen IV nuclear reactors. In the present investigation, a comparative study of the effect of autogenous tungsten inert gas welding (A-TIG) with double pass and multipass gas tungsten arc (GTA) welding with filler on microstructure evolution in the weld fusion zone and the mechanical properties of P91 and P92 steel welded joints was carried out. The microstructure evolution was studied in as-welded and postweld heat treatment (PWHT) condition. The study also focused on the evolution of d-ferrite patches and their influence on the tensile properties of welded joints. PWHT was carried out at 760 C with durations from 2 to 6 h. To study the effect of d-ferrite evolution on mechanical properties, Charpy toughness, microhardness, and tensile tests were performed. The acceptable microstructure and mechanical properties were obtained after the 6 h of PWHT for A-TIG arc welding process while for GTA weld with filler wire, it was obtained after the 2 h of PWHT at 760 C. � 2018 by ASME.