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Arun Kumar Bhaduri - One of the best experts on this subject based on the ideXlab platform.

  • Repair Welding of cracked turbine shroud using matching composition consumables
    Science and Technology of Welding and Joining, 2005
    Co-Authors: C. R. Das, Arun Kumar Bhaduri, V. Ramasubbu, S.k. Ray
    Abstract:

    Abstract Repair Welding of a crack in the III-stage shroud of a high pressure turbine, was carried out using matching composition ER 410 filler wire by the gas tungsten arc Welding (GTAW) process with ultra high purity argon as shielding and backing gas. The development of the Repair Welding procedure involved laboratory studies for the selection of a suitable ER410 filler wire, optimisation of Welding parameters and PWHT. Mock up Welding under simulated on-site constraints confirmed the feasibility to produce in situ sound weld joint. In situ Repair Welding and localised PWHT was carried out successfully. NDT and in situ metallography of the Repair-welded region confirmed adequate tempering of the martensitic weldment during the localised PWHT.

  • Recent trends in Repair and refurbishing of steam turbine components
    Sadhana, 2003
    Co-Authors: Arun Kumar Bhaduri, S.k. Ray, S. K. Albert, P. Rodriguez
    Abstract:

    The Repair and refurbishing of steam generator components is discussed from the perspective of Repair Welding philosophy including applicable codes and regulations. Some case histories of Repair Welding of steam generator components are discussed with special emphasis on details of Repair Welding of cracked steam turbine blades and shrouds in some of the commercial nuclear power plants using procedures developed.

  • In situ Repair Welding of steam turbine shroud for replacing a cracked blade
    Journal of Materials Engineering and Performance, 2002
    Co-Authors: Shaju K. Albert, V. Ramasubbu, Arun Kumar Bhaduri
    Abstract:

    A root-cracked blade in a high-pressure steam turbine of a nuclear power plant had to be replaced with a new blade by cutting the shroud to remove the cracked blade. This necessitated in situ Welding of a new shroud piece with the existing shroud after the blade replacement. The in situ Welding of the shroud, a 12% Cr martensitic stainless steel with tempered martensite microstructure, was carried out using gastungsten arc Welding and 316L austenitic stainless steel filler metal followed by localized postweld heat treatment at 873 K for 1 h using a specially designed electrical resistance-heating furnace. Mock-up trials were carried out to ensure that sound welds could be made under the constraints present during the in situ Repair Welding operation. In situ metallography of the Repair weld after postweld heat treatment confirmed the adequate tempering of the martensitic structure in the heat-affected zone. Metallurgical investigations carried out in the laboratory on a shroud test-piece that had been welded using the same procedure as employed in the field confirmed the success of the in situ Repair operation. The alternate option available was replacing the cracked blade and the shroud piece to which it is riveted with a new one, reducing the height of all the blades attached to the shroud by machining, riveting the blades with reduced height to the new shroud, and, finally, dynamic balancing of the entire turbine after completion of the Repair. This option is both time-consuming and expensive. Hence, the successful completion of this Repair Welding resulted in enormous savings both in terms of reducing the downtime of the plant and the cost of the Repair. The turbine has been put back into service and has been operating satisfactorily since December 2000.

  • Repair Welding of cracked steam turbine blades using austenitic and martensitic stainless-steel consumables
    Nuclear Engineering and Design, 2001
    Co-Authors: Arun Kumar Bhaduri, T. P. S. Gill, K. Shanmugam, Shaju K. Albert, D.r Iyer
    Abstract:

    The procedure for Repair Welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc Welding process. Weld Repair procedures were developed using both ER 316L austenitic and ER 410 martensitic stainless-steel filler wire. The overall development of the Repair Welding procedure included selection of Welding consumables (for austenitic filler metal), optimisation of post-weld heat treatment parameters, selection of suitable method for local pre-heating and post-weld heat treatment (PWHT) of the blades, determination of mechanical properties of weldments in as-welded and PWHT conditions, and microsturctural examination. After various trials using different procedures, the procedure of local PWHT (and preheating when using martensitic stainless-steel filler wire) using electrical resistance heating on the top surface of the weldment and monitoring the temperature by placing a thermocouple at the bottom of the weld was found to give the most satisfactory results. These procedures have been developed and/or applied for Repair Welding of cracked blades in steam turbines.

  • Evaluation of Repair Welding procedures for 2.25Cr–1Mo and 9Cr–1Mo steel welds
    Science and Technology of Welding and Joining, 2001
    Co-Authors: Arun Kumar Bhaduri, T. P. S. Gill, Sanjay Rai, S. Sujith, T. Jayakumar
    Abstract:

    AbstractChromium–molybdenum steels are extensively used in the steam generator circuits of power plants. These components may require Welding of the cracks that can develop during fabrication, storage, and transportation stages, or during the service life of the plant. This investigation compares Repair Welding methods for Cr–Mo steels, using 2.25Cr–1Mo and 9Cr–1Mo materials. To simulate aging during service, welds were heat treated at 873 K for 5000 h. Simulated Repair Welding of the aged welds was carried out at the weld/base metal interface, i.e. at the location at which cracks are usually reported to occur during service. Two Repair Welding methods (half bead and butter bead temper bead methods) conforming to the ASME Boiler and Pressure Vessel Code were used. Tensile properties, hardness profiles, and X-ray diffraction based residual stress distributions were determined for both the Cr–Mo steel welds to evaluate the simulated Repair welds. Analysis of the test results showed that both the Repair weld...

V.s. Raja - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Repair Welding on Electrochemical Corrosion and Stress Corrosion Cracking Behavior of TIG Welded AA2219 Aluminum Alloy in 3.5 Wt Pct NaCl Solution
    Metallurgical and Materials Transactions A, 2010
    Co-Authors: A. Venugopal, K. Sreekumar, V.s. Raja
    Abstract:

    The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and Repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio ( ε _NaCl/( ε _air)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one Repair Welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

  • effect of Repair Welding on electrochemical corrosion and stress corrosion cracking behavior of tig welded aa2219 aluminum alloy in 3 5 wt pct nacl solution
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2010
    Co-Authors: A. Venugopal, K. Sreekumar, V.s. Raja
    Abstract:

    The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and Repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio (eNaCl/(eair)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one Repair Welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

Maurizio Vedani - One of the best experts on this subject based on the ideXlab platform.

  • problems in laser Repair Welding a surface treated tool steel
    Surface & Coatings Technology, 2007
    Co-Authors: Maurizio Vedani, Barbara Previtali, G Vimercati, A Sanvito, G Somaschini
    Abstract:

    A research work is described on the development of defects in laser Repair Welding of a surface-treated tool steel. Repair Welding tests were carried out on plasma-nitrided and on chrome-plated type 1.2738 steel plates. Welding defects in the chrome-plated samples were mainly due to chrome and oxygen overalloying of the weld metal, leading to extensive hot cracking. Cracks of the surface chrome deposit in the HAZ due to Welding stresses were also detected. In the nitrided samples, Welding resulted in the copious formation of gas pores due to nitrogen release during weld metal solidification. A procedure for combined laser pre-treating and laser Welding of the nitrided samples was thus presented. The procedure is aimed at minimising the negative effect of the laser beam on the structural integrity of the base and welded material. The results of the microstructural analyses revealed that a significant reduction in defects could be achieved by the proposed method in the nitrided samples.

  • Microstructural evolution of tool steels after Nd-YAG laser Repair Welding
    Journal of Materials Science, 2004
    Co-Authors: Maurizio Vedani
    Abstract:

    The present paper is aimed at investigating the microstructural behaviour of tool steels after Repair Welding or refurbishing by a pulsed Nd-YAG precision laser. The 1.2311 (40CrMnMo7), 1.2083 (X42Cr13) and 1.2343 (X38CrMoV5-1) steels were selected for experimental investigations to cover a wide range of steel grades, commonly used in tooling industry. Laser Repair Welding condition was simulated by preparing small deposits in one or more passes on steel samples having several reference geometries. Investigations on microstructural properties, microhardness evolution and on defect formation were carried out. The effects of different laser Welding parameters were also considered. The study allowed to state several fundamental information on tool behaviour during Repair Welding in order to gain a deeper insight into this process, routinely considered in industrial practice but often neglected in scientific research works on Welding metallurgy.

A. Venugopal - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Repair Welding on Electrochemical Corrosion and Stress Corrosion Cracking Behavior of TIG Welded AA2219 Aluminum Alloy in 3.5 Wt Pct NaCl Solution
    Metallurgical and Materials Transactions A, 2010
    Co-Authors: A. Venugopal, K. Sreekumar, V.s. Raja
    Abstract:

    The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and Repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio ( ε _NaCl/( ε _air)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one Repair Welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

  • effect of Repair Welding on electrochemical corrosion and stress corrosion cracking behavior of tig welded aa2219 aluminum alloy in 3 5 wt pct nacl solution
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2010
    Co-Authors: A. Venugopal, K. Sreekumar, V.s. Raja
    Abstract:

    The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and Repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio (eNaCl/(eair)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one Repair Welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

Shantung Tu - One of the best experts on this subject based on the ideXlab platform.

  • finite element analysis of the effect of Welding heat input and layer number on residual stress in Repair welds for a stainless steel clad plate
    Materials & Design, 2011
    Co-Authors: Wenchun Jiang, B Y Wang, Jianming Gong, Shantung Tu
    Abstract:

    Stainless steel clad plate is widely used in petroleum, chemical and medicine industries due to its good corrosion resistance and high strength. But cracks are often formed in clad layer during the manufacture or service, which are often Repaired by Repair Welding. In order to ensure the structure integrity, the effects of residual stress need to be considered. The objective of this paper is to estimate the residual stress and deformation in the Repair weld of a stainless steel clad plate by finite element method. The effects of heat input and Welding layer number on residual stresses and deformation have been studied. The results show that large residual stresses have been generated in the Repair weld. The heat input and layer number have great effects on residual stress distribution. With the heat input and Welding layer number increasing, the residual stresses are decreased. Using multiple-layer Welding and higher heat input can be useful to decrease the residual stress, which provides a reference for optimizing the Repair Welding technology of this stainless steel clad plate.