Research Publications
Permanent URI for this collectionhttps://idr.iitbbs.ac.in/handle/2008/2
Browse
50 results
Search Results
Item Microstructure and mechanical properties of D-Gun sprayed Cr3C2-NiCr coating on P91 steel subjected to long term thermal exposure at 650 �c(2019) Thakare J.G.; Pandey C.; Mulik R.S.; Mahapatra M.M.Thermally sprayed 75Cr3C2-25NiCr coating is applied on structural components to improve corrosion, oxidation and erosion behaviour at high temperature. In order to understand the microstructural and mechanical behaviour of coating a long term investigation was carried out at 650 �C. The Objective of the present work is to study the effect of long term heat treatment (i.e. 650 �C/ 3000 h) on various characteristics of the detonation gun sprayed 75Cr3C2-25NiCr coating. Hardness and nanoindentation studies were carried out on Cr3C2-NiCr coating after fixed time intervals. The morphological and microstructural features of the coated surface were characterized using scanning electron microscope (SEM). The phases formed during the long term exposure were identified by x-ray diffraction (XRD) technique. The coating showed the presence of various Cr, Ni, based oxides, Fe and Ni based spinels. Vanadium, niobium, and molybdenum showed maximum tendency to diffusion from substrate to the coating. Hardness of the coating reached a maximum value of 870 HV after 2160 h of exposure. The hardness of coating observed an initial drop in hardness due to carbide coarsening which was recovered by precipitation of carbides from the solid solution. � 2019 IOP Publishing Ltd.Item An assessment for mechanical and microstructure behavior of dissimilar material welded joint between nuclear grade martensitic P91 and austenitic SS304 L steel(2019) Thakare J.G.; Pandey C.; Mahapatra M.M.; Mulik R.S.The microstructural evolution and mechanical properties of gas tungsten arc welded creep strength enhanced martensitic (CSEM) and austenitic stainless steel (SS) dissimilar welded joint is explored in the as welded (AW) and post weld heat treated (PWHT) conditions. The as received normalized and tempered P91 steel has been welded with SS304 L by preparing a conventional groove and employing a P91 GTAW filler wire. The welded plate is subjected to PWHT at 760 �C for 120 min followed by air cooling. The P91 steel in as received condition exhibited fully martensitic (tempered) structure with lathe morphology and prior austenite grain boundaries while SS304 L have austenitic structure with twins. The heterogeneity (as-welded condition) across the welded joint were produced in terms of microstructure and mechanical properties (hardness, Charpy toughness and tensile strength). The variation in mechanical properties has been minimized after the PWHT. PWHT has observed a drastic influence on mechanical properties and microstructure of weld fusion zone and HAZ of P91 side however, remain unaffected for the SS304 L side HAZ. The strength of the welded joint have been measured 1016 � 2.5 MPa and 906 � 6.5 in as-welded and PWHT condition with joint efficiency of 140 % and 125 %, respectively. � 2019 The Society of Manufacturing EngineersItem 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.Item 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. � 2018Item Thermomechanical analysis of tungsten inert gas welding process for predicting temperature distribution and angular distortion(2019) Narang H.K.; Pandey C.; Thakare J.G.; Saini N.; Mahapatra M.M.; Jha P.K.In present research work, discussions have been made to predict the bead geometries and shape profiles of weldments using statistical regression modeling and fuzzy logic techniques. However, the regression and fuzzy logic modeling techniques do not take into account the actual physical properties and phenomena that occur in welding. Moreover, techniques such as regression and fuzzy logic modeling are not suitable for predicting the transient temperature distribution and distortion of arc welded joints. To predict the transient temperature distributions, peak temperature distribution, and residual deformation in welding, deterministic modeling techniques such as thermomechanical analysis are preferred. However, while performing thermomechanical analysis of welded joints, size and reinforcement dimensions of the weld bead need to be incorporated into the model for accurate prediction of transient temperature distributions and distortions. In this work, circularly spread moving heat source has been used for transient thermal modeling of tungsten inert gas (TIG) welding process. In the subsequent sections of this article, the weld thermomechanical analyses for TIG square butt joints are discussed to predict the temperature distributions and angular distortion. The weld dimensions such as weld width, weld depression, and weld bulging have shown great influence on the angular distortion patterns. � 2019 Society of Naval Architects and Marine Engineers. All rights reserved.Item Study on effect of double austenitization treatment on fracture morphology tensile tested nuclear grade P92 steel(2019) Pandey C.; Mahapatra M.M.; Kumar P.; Kumar P.; Saini N.; Thakare J.G.; Kumar S.Effect of �conventional normalizing and tempering� (CNT) and �double austenitization based normalizing and tempering� (DNT) process on microstructure characteristic and mechanical behavior was studied forP92 steel. In CNT heat treatment, P92 steel is normalized at 1040 �C/air cool and tempered with 760 �C/2 h/air cool. In DNT heat treatment, initially normalizing was performed at 1040 �C for 1 h followed by water quenching. After that sample was normalized in the temperature range of 950�1150 �C for 1 h and tempered at 760 �C/2 h/air cool (950 �C-DNT1, 1050 �C-DNT2, 1150 �C-DNT3).Grain size for CNT and DNT1 treatment were measured 17 � 7 ?m and 12 � 5 ?m. A DNT treatment resulted in homogeneous microstructure formation that led to improved mechanical properties as compared to CNT treatment. The DN based heat treatment produced complete martensitic microstructure formation by complete dissolution of carbide precipitates. The optimized room temperature condition was obtained for the DNT 1 heat treatment. � 2018 Elsevier LtdItem Softening mechanism of P91 steel weldments using heat treatments(2019) Pandey C.; Mahapatra M.M.; Kumar P.; Daniel F.; Adhithan B.The tungsten inert gas welded P91 steel welded joints were subjected to the two different type of heat treatments including the postweld direct tempering (PWDT) and re-austenitizing based tempering (PWNT) treatment. The microstructure of weld fusion and heat affected zone (HAZ) were characterized in different heat treatment conditions using optical microscope and scanning electron microscope. For as-welded joint, a great heterogeneity was observed in microstructure and mechanical properties across the weldments. The Charpy toughness of the as-welded joint was measured much lower than the minimum recommended value of 47 J and it was measured 8 � 5 J. The PWHTs have found a beneficial effect in decreasing the microstructure heterogeneity across the welded joint and improving the mechanical properties. The PWDT resulted in a drastic improvement in the Charpy impact toughness of the welded joint and it was measured 59 � 5 J which was higher than the minimum required value of 47 J but still inferior than the base metal. The ? ferrite still remained in overlap zone of the weld fusion zone. The PWNT treatment resulted in homogeneous microstructure and hardness variation across the welded joint in transverse direction and Charpy impact toughness (149 � 6 J) exceeded than that achieved in base metal. � 2018 Politechnika Wroc?awskaItem 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.Item 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?awskaItem Characterization of slurry-based mullite coating deposited on P91 steel welds(2019) Kanwal S.; Thakare J.G.; Pandey C.; Singh I.; Mahapatra M.M.Ceramic coatings are widely used as thermal and environment barrier coatings due to their inert properties and capability to withstand high temperature. Ceramic coatings are commonly deposited by air plasma spray process and electron beam physical vapor deposition. In the present work, a cost-effective, slurry-based dip coating technique was developed to deposit mullite-based ceramic coating on the P91 steel substrate. The coating has been characterized by X-ray diffraction technique and scanning electron microscopy. Sintering of coatings was carried out in the temperature range of 900�1000��C. Sintering time was varied between 0.5 and 1�h. Energy dispersive spectroscopy was carried out to study the distribution and diffusion of constituent elements during high-temperature sintering. Potentiodynamic polarization tests and thermo-gravimetric analysis were performed to investigate the corrosion behavior of the coating. The coating sintered at 1000��C was found to be free from cracks and other microdefects. The corrosion rate of coating sintered at 1000��C was found to be 26.06�mpy whereas the uncoated sample showed a higher corrosion rate of 153.7�mpy. � 2018, Australian Ceramic Society.