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Microstructure and Transverse Shrinkage Stress Analysis in GTA Welds of P91 Steel Pipe
Chandan Pandey 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2
In a steam power plant, several components such as boiler tube, condenser and steam lines are made of high creep resistant steel. The P91 steel pipes are generally used in steam power plant because of high creep strength at service temperature of approximately 600oC. In the present research work, the study about shrinkage stresses and their distribution in the four quadrants of P91 pipe weld of 11 mm thickness is reported. The conventional-V and narrow-groove welds were prepared by using the gas tungsten arc welding (GTAW) process. Welding current, arc voltage, groove design, and straining length were the main parameters that affect the transverse shrinkage stresses. In the present research work, the effect of groove design on transverse shrinkage stresses has been evaluated. It also describes the effect of the number of passes on shrinkage. It is concluded that, for a given heat input, the narrow groove pipe weld joint exhibits comparatively less transverse shrinkage stress. Scanning electron microscope (SEM) with field emission gun and optical microscope has been used to characterize the weld fusion zone and HAZs of P91 pipe weldments.
Chandan Pandey,M. M. Mahapatra,Pradeep Kumar,A. Giri 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5
The effect of weld groove design and heat treatment on microstructure evolution and Charpy toughness of P91pipe weldments was studied. The P91 pipe weldments were subjected to subcritical post weld heat treatment(760 °C-2 h) and normalizing/tempering conditions (normalized-1040 °C/40 min, air cooled; tempered 760 °C/2 h,air cooled) were employed. The influence of subsequent PWHT and N&T treatment on the microstructure of variouszone of P91 pipe weldments were also investigated. The present investigation also described the effect ofPWHT and N&T treatment on hardness, grain size, precipitate size, inter-particle spacing and fraction area of precipitatespresent in each zone of P91 pipe weldments. The result indicated great impact of heat treatment on theCharpy toughness and microstructure evolution of P91 weldments. The N&T treatment was found to be moreeffective heat treatment compared to subsequent PWHT. Charpy toughness value was found to be higher for narrow-groove design as compared to conventional V-groove design.
Thermal Barrier Coatings—A State of the Art Review
Jayant Gopal Thakare,Chandan Pandey,M. M. Mahapatra,R. S. Mulik 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
Thermal barrier coatings (TBCs) have seen considerable advancement since the initial testing and development of thermalspray coating. Thermal barrier coatings are currently been utilized in various engineering areas which include internal combustion engines, gas turbine blades of jet engines, pyrochemical reprocessing units and many more. The development of newmaterials, deposition techniques is targeted at improving the life of the underlying substrate. Hence, the performance of thecoating plays a vital role in improving the life of substrate. The scope for advancement in thermal barrier coatings is veryhigh and continuous eforts are being made to produce improved and durable coatings. Thermal barrier coatings have thepotential to address long term and short-term problems in gas turbine, internal combustion and power generation industry. The study of thermal barrier coating material, performance and life estimation is a critical factor that should be understood tointroduce any advancement. The present review gives an overview of the thermal spraying techniques and current advancements in materials, mechanical properties, understanding the high temperature performance, residual stress in the coating,understanding the failure mechanisms and life prediction models for coatings.
Bhanu Vishwa,Gupta Ankur,Pandey Chandan 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8
The need for Dissimilar Welded Joint (DWJ) in the power plant components arises in order to increase the overall efficiency of the plant and to avoid premature failure in the component welds. The ActivatedTungsten Inert Gas (A-TIG) welding process, which is a variant of Tungsten Inert Gas (TIG) welding, is focus of this review work concerning the DWJ of nuclear grade creep-strength enhanced ferritic/ martensitic (CSEF/M) steels and austenitic steels. A-TIG DWJs are compared with Multipass-Tungsten Inert Gas (M-TIG) DWJ based on their mechanical and microstructural properties. The limitations of multipass welding have put A-TIG welding in focus as A-TIG provides a weld with increased depth of penetration (DOP) and enhanced mechanical properties. Hence, this review article covers the A-TIG welding principle and working parameters along with detailed analysis of role played by the flux in welding procedure. Further, weld characteristics of martensitic and austenitic steel DWJ developed with the A-TIG welding process and the M-TIG welding process are compared in this study as there are differences in mechanical, microstructural, creep-related, and residual stress obtained in both TIG variants. The mechanics involved in the welding process is deliberated which is revealed by microstructural changes and behavior of base metals and WFZ
P. K. Taraphdar,Rajiv Kumar,Chandan Pandey,M. M. Mahapatra 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
In the present study, different finite element (FE) models were prepared to investigate weld induced residual stresses inthick multi-pass butt welded joint of SA516 Gr. 70 plates. Both 3D and 2D full geometry models and their axisymmetrichalf models were taken into consideration. The competence of these FE models on the accuracy of predicting residual stressdistribution across the weld cross-section was investigated by comparing it with the experimental results. Blind hole drillingtechnique and deep hole drilling technique were employed to evaluate the surface and through-thickness residual stressdistributions, respectively. In addition, the change in volume and yield strength of weld material due to austenitic phasetransformation was also incorporated in the material modeling to observe the effect of solid-state phase transformation(SSPT) on the evaluation of residual stresses. Computed residual stresses obtained from different FE models indicate thatthe 3D FE models procured the best accuracy compared with the experimental results. On the other hand, 2D models cansave a significant amount of computational time with reasonable accuracy. Incorporation of SSPT in the 3D FE full modelexhibited a better agreement of predicted results with the experimental measurements.