Browsing by Author "Saini N."

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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.
A brief study on ?-ferrite evolution in dissimilar P91 and P92 steel weld joint and their effect on mechanical properties
(2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.; Thakre J.G.; Vidyarthy R.S.; Narang H.K.
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 joint of P91 and P92 steel were prepared using the autogenous tungsten inert gas (A-TIG) welding and multi-pass gas tungsten arc welding (GTAW) process. A comparative study was performed on evolution of ?-ferrite patches in weld fusion zone and heat affected zones (HAZs) of welded joints. The evolution of ?-ferrite patches was studied in as-welded and post-weld heat treatment (PWHT) condition. PWHT was carried out at 760 �C for tempering time of 2 h and 6 h, for both A-TIG and GTA weld joints. It was observed that presence of higher content of ferrite stabilizer in P92 steel promote the formation of ?-ferrite patches in weld fusion zone as well as HAZs. To study the effect of welding process and PWHT, Charpy V impact energy and microhardness tests were performed. For microstructure characterization, field-emission scanning electron microscope (FESEM) and optical microscope were utilized. � 2017 Politechnika Wroc?awska
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.
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
Characterization of P92 Steel weldments in as-welded and PWHT conditions: Room-temperature tensile tests and microhardness measurements led to improving the ductility of the weld joints
(2018) Saini N.; Pandey C.; Mahapatra M.M.; Mulik R.S.
P92 steels have been developed as a candidate material for power plant components that operate in a temperature range of 620o-650�C. A heterogeneous microstructure formation across the P92 weldments makes the wettability of P92 steel a serious issue. The other problem that arises in P92 steel weldments is the formation of ?-ferrite due to the presence of a higher weight percentage of ferrite stabilizers such as V and Nb. as well as W and Mo. In the present work, the shielded metal arc welding (SMAW) process was utilized to prepare the P92 steel weld joints. After welding, postweld heat treatment (PWHT) was performed at 760�C for 2 h. To characterize the weld joints, room-temperature tensile tests and microhardness measurements were performed in the as-welded and PWHT conditions. The subsequent PWHT resulted in a decrease in the hardness gradient across the weldments. The PWHT resulted in enhancing the : ductility of the weld joints. � 2018 American Welding Society. All rights reserved.
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.
A comparative study of ductile-brittle transition behavior and fractography of P91 and P92 steel
(2017) Saini N.; Pandey C.; Mahapatra M.M.; Narang H.K.; Mulik R.S.; Kumar P.
The modified 9Cr-1Mo (P91) and 9Cr- 0.5Mo- 1.8W (P92) steel used in fast breeder reactor is exposed to irradiation during service which severely affects the dynamic fracture resistance by increasing the ductile to brittle transition temperature (DBTT). Thus, even at room temperature, the steel can become brittle and prone to cracking. In the present investigation, to elucidate the influence of low temperature on the DBTT, Charpy toughness test was performed on creep strength enhanced ferritic P91 and P92 steel. Lower DBTT was observed for the P92 steel as compared to P91 steel. To find the mode of fracture, the fractured Charpy toughness specimens were investigated using a field electron scanning electron microscope (FESEM). The fracture surface revealed the brittle mode of fracture at a lower temperature for both the steels while the mixed mode of fracture was noticed at room temperature and above. � 2017 Elsevier Ltd
Corrigendum to �A brief study on ?-ferrite evolution in dissimilar P91 and P92 steel weld joint and their effect on mechanical properties� [Archives of Civil and Mech Engineering 18 (2018)713�722](S1644966517301814)(10.1016/j.acme.2017.12.002)
(2019) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.; Thakare J.G.; Vidyathy R.S.; Narang H.K.
The authors regret that The authors regret for any inconvenience caused. � 2019 Politechnika Wroc?awska
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
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)
Effect of creep phenomena on room-temperature tensile properties of cast & forged P91 steel
(2017) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
In present research work, the as-received cast & forged (C&F) P91 steel was subjected to the creep test at temperature of 620 �C and 650 �C for applied stress of 120 MPa. The room temperature tensile test was conducted after normalizing and tempering (N&T) treatment of the ruptured creep specimen. The standard tensile-test specimen was prepared from the gauge section of creep ruptured specimen. The N&T treatment was performed to restore the microstructure and mechanical properties of virgin P91 steel (N&T P91 steel). The microstructure of creep fractured specimen in ruptured state and N&T condition were characterized by using field-emission scanning electron microscope (FE-SEM) with energy dispersive X-ray spectroscopy (EDS). The fracture surface morphology of crept specimen and the tensile tested specimen was also studied. The effect of prior creep deformation on the mechanical strength was more significant in the sample with longer creep rupture life. � 2017
Effect of diffusible hydrogen content on embrittlement of P92 steel
(2017) Saini N.; Pandey C.; Mahapatra M.M.
In the present investigation, varying electrode conditions (dried and contaminated) have been employed during welding of P92 steel to study the effect of diffusible hydrogen level on hydrogen-assisted cracking (HAC). Shielded metal arc welding process was employed to deposit the metal on a P92 steel plate. To evaluate HAC, the Granjon implant test with varying diffusible hydrogen content in the deposited metal was utilized. The diffusible hydrogen level was measured in the deposited metal by using the mercury method. Lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio were evaluated from the Granjon implant test. The fracture surface morphology of fractured implant specimens has been studied by using a field emission secondary electron microscope. The P92 steel plate welded by the contaminated electrode with a high level of diffusible hydrogen was found to be more susceptible to HAC. As diffusible hydrogen content increased in the deposited metal, the LCS value and EI were observed to be decreased. � 2017 Hydrogen Energy Publications LLC
Effect of normalization and tempering on microstructure and mechanical properties of V-groove and narrow-groove P91 pipe weldments
(2017) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
In Very High Temperature Reactor (VHTR), The Nb-V modified 9Cr-1Mo (P91) creep strength enhanced ferritic (CSEF) steel is currently considered as a candidate material for reactor internals and reactor pressure vessels (RPVs). After the welding of P91 steel, the inhomogeneous microstructure of weldment is a serious issue because it promotes the well-known Type IV cracking in P91 weldments. The present research work is focused on how the microstructure evolve in various zone of P91 pipe weldment during the sub-critical post weld heat treatment (PWHT) and normalized and tempered (N&T) heat treatment. The effect of PWHT and N&T heat treatment are also considered on tensile properties and hardness variation of P91 weldments. To characterize the sample scanning electron microscope (SEM), X-ray diffraction (XRD) and optical micrograph was used. It was observed that the N&T heat treatment provides the homogeneous microstructure compared to PWHT. The superior mechanical properties was also measured in N&T condition compared to PWHT. Study of fracture surface morphology of tensile tested specimen in different heat treatment condition is also presented. � 2017 Elsevier B.V.
Effect of Normalizing Temperature on Fracture Characteristic of Tensile and Impact Tested Creep Strength-Enhanced Ferritic P92 Steel
(2017) Saini N.; Pandey C.; Mahapatra M.M.
The high-temperature Cr-Mo creep strength-enhanced ferritic (CSEF) steels are mainly used in nuclear and thermal power plants. In the present investigation, a systematic study on fracture surface morphologies of tensile and impact tested specimens and mechanical properties of cast and forged (C&F) P92 steel was performed for various heat treatment conditions. The heat treatment was carried out in normalizing temperature range of 950-1150��C and then tempered to a fixed tempering temperature of 760��C. The effect of varying normalizing temperatures before and after tempering on microstructure evolution, tensile properties, Vicker�s hardness and Charpy toughness was studied. The normalizing temperature before and after tempering was having a noticeable effect on mechanical properties of as-received P92 steel. The fracture surface of impact and tensile tested samples was also studied for various normalizing temperatures with or without tempering. Fracture surface morphology was affected by the presence of secondary phase carbide particles. The fraction area of cleavage facets on the tensile fracture surface was found to be increased with an increase in the normalizing temperature. The fractured tensile specimens were characterized by transgranular ductile dimples, tear ridges and transgranular cleavage facets for various heat treatments. The fracture mode of impact tested samples was more complex. It showed both quasi-cleavage facets and ductile dimple tearing for various normalizing temperatures. � 2017, ASM International.
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.
Effect of Weld Consumable Conditioning on the Diffusible Hydrogen and Subsequent Residual Stress and Flexural Strength of Multipass Welded P91 Steels
(2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.
P91 steel weld joint was prepared using the shielded metal arc welding process and four different conditions of weld consumable that provide the different levels of diffusible hydrogen in deposited metal. In the present research, the effects of diffusible hydrogen content on the flexural strength, lower critical stress, and tensile strength of P91 steel welds were also determined with respect to different electrode conditions. To investigate the effect of diffusible hydrogen on multipass welding, top and root side flexural tests were performed. The residual stresses (axial stress and transverse stress) were also measured using the blind hole drilling method for different conditions of welding consumable. The peak value of residual stresses was measured at the center of the weld fusion zone. The maximum value of transverse stress was measured to be 355�MPa for case II (6.21�mL/100 g of diffusible hydrogen), while the maximum axial stress was about 218�MPa for case IV (12.43�mL/100�g of diffusible hydrogen). A three-dimensional finite element simulation was also performed to predict the residual stress distribution and thermal profile along the welded joint. The experimentally determined residual stresses correlated well with the numerically estimated residual stresses. The diffusible hydrogen content was not observed to have any significant effect on the residual stresses. The corrected residual stress values were also predicted by considering the plasticity-induced error. However, the flexural performance of the welded joint was affected by the diffusible hydrogen content. The top and root flexural strength was measured to be optimum for the low level of diffusible hydrogen content, and the values decreased with an increase in diffusible hydrogen content. � 2018, The Minerals, Metals & Materials Society and ASM International.
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.
Estimation of strength and wear properties of Mg/SiC nanocomposite fabricated through FSP route
(2017) Deepan M.; Pandey C.; Saini N.; Mahapatra M.M.; Mulik R.S.
The present paper discusses the effects of friction stir processing (FSP) on properties of Mg�SiC nanocomposite. The magnesium-based RZ5 alloy, widely used for aerospace applications, was used in the present investigation as the matrix for the purpose of nanocomposite fabrication. SiC powders of nanosize were reinforced into the RZ5 matrix by FSP with varying process parameters. The process was studied with respect to the effects of parameters such as rotational speed, traverse rate, and number of passes on the nanocomposite. With appropriate parameters, uniform distribution of nanoSiC reinforcements was accomplished in the metal matrix. The abrasive wear property of the Mg�SiC nanocomposite was verified with respect to the FSP process parameters. A mathematical model was also developed to predict the strength and abrasive wear characteristics of the nanocomposite with respect to the FSP parameters. � 2017, The Brazilian Society of Mechanical Sciences and Engineering.
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.
Grain refinement of P91 steel using double austenitization treatment
(2018) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.; Thakre J.G.; Kumar P.
The effect of conventional normalizing and tempering (CNT) and double austenitization-based normalizing and tempering (DNT) heat treatments on the microstructure evolution and mechanical properties of creep strength-enhanced ferritic P91 steel were studied. CNT treatment was performed at 1,050�C and air cooled for 1 h and also at 760�C and air cooled for 2 h. In double austenitization- based normalizing heat treatment, steel was austenitized at 1,050�C and air cooled for 1 h and then normalized in a temperature range of 950�C -1,150�C for 1 h followed by water quenching. After the double normalizing, tempering is performed at 760�C for 2 h. A DNT treatment resulted in homogeneous microstructure formation that led to improved mechanical properties as compared to CNT treatment. The incomplete dissolution of precipitates in single-stage tempering resulted in incomplete martensitic structure formation. � 2018 by ASTM International.