Browsing by Author "Thakre J.G."

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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
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)
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.
Nano-size Particle Evolution During Heat Treatment of P91 Steel and Their Effect on Micro Hardness
(2017) Pandey C.; Mahapatra M.M.; Kumar P.; Saini N.; Thakre J.G.
In the present research work, creep strength enhanced ferritic/martensitic P91 steel was subjected to varying normalizing (950�1150 �C) and tempering temperature (730�800 �C). The varying normalizing and tempering temperature effect on microstructure evolution (precipitate size and their distribution and grain size) and microhardness were performed. The heat treatment consequences on microstructure evolution revealed an increase in grain size, and decrease in fraction area of precipitates, with increase in normalizing temperature. The grain size was found to be decreased with increase in tempering temperature while fraction area of precipitates and precipitate diameter increased. For microstructure characterization, optical microscope and field emission scanning electron microscope were utilized. The microhardness was found to be increased with increase in normalizing temperature while it decreased with increase in tempering temperature. � 2017 The Indian Institute of Metals - IIM
Role of evolving microstructure on the mechanical behaviour of P92 steel welded joint in as-welded and post weld heat treated state
(2019) Pandey C.; Mohan Mahapatra M.; Kumar P.; Thakre J.G.; Saini N.
An autogenous gas tungsten arc welded P92 weld joint was subjected to two different post weld heat treatment (PWHT). One PWHT involved tempering of the as-welded sample at 760 �C for 2 h (referred to as PWDT) followed by natural air cooling. The other PWHT involved normalizing (re-austenitizing) the as-welded sample at 1040 �C for 40 min followed by PWDT (referred as PWNT). The cross-section of the as-welded sample exhibited a higher degree of microstructural heterogeneity. Both the PWDT and PWNT heat treatment procedures reduced the heterogeneity gradient along the weld cross section. The heat affected zone (HAZ) of the as-welded and PWDT samples showed Charpy toughness values of 3 � 4 J and 64 � 6 J, respectively, which were lower than that of the base metal (72 � 5 J). The PWNT treated sample exhibited a HAZ Charpy toughness value of 83 � 4 J which was higher than that of the base metal. The brittle mode of the fracture with river patterns was observed for the as-welded and PWDT treated sample while a ductile mode of fracture with fine and shallow dimples was observed for the PWNT condition. The PWNT treatment resulted in dissolution of the ferrite patches and formation of a uniform microstructure along the weld cross section. The PWNT treated samples exhibited the lowest yield strength to tensile strength ratio supporting the enhanced ductility as a result of this re-austenizing heat treatment. The as-welded and PWDT treated weld joints showed the presence of detrimental ? ferrite phase in the weld fusion zone and the coarse grained heat affected zone. The PWNT completely removed the ? ferrite patches from the microstructure whereas the PWDT treatment merely reduced the range of the hardness of the ? ferrite from 179 to 301 HV (as welded) to 204�228 HV. � 2018 Elsevier B.V.
Study on Hydrogen-Assisted Cracking in High-Strength Steels by Using the Granjon Implant Test
(2017) Yadav U.; Pandey C.; Saini N.; Thakre J.G.; Mahapatra M.M.
In present research work, the modified Granjon implant test was performed to evaluate the susceptibility of AISI 8620 and AISI 304 steels toward the hydrogen-assisted cracking. To measure the diffusible hydrogen level (HD) in deposited metal, glycerin method was employed. Shielded metal arc welding process with basic type electrode was used to deposit the metal. The hydrogen was intentionally introduced for the plate of the material AISI 304 by using an oil of grade Society of Automotive Engineers 10, which is of very low viscosity. The heat-affected zone susceptibility was quantified by finding the lower critical stress for a measured hydrogen content. � 2017, Springer Science+Business Media New York and ASM International.