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Bhaduri, Arun Kumar
- Dilatometric Study of Phase Transformation and Thermal Expansion in T91 Steel
Authors
1 Metallurgy & Materials Group Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, IN
Source
Indian Welding Journal, Vol 48, No 3 (2015), Pagination: 31-31Abstract
A comprehensive characterization of the kinetic aspects of diffusional α'-martensite-> α - ferrite+carbides -> γ vaustenite phase transformation that occurs during heating and that of γ ->α '-martensite displacive phase transformation, which occurs upon continuous cooling has been performed using high resolution dilatometry, under varying thermal history. The results of dilatometry are analysed in terms of an appropriate thermo-kinetic framework to obtain useful information about transformation temperatures, their dependence on thermal history, and apparent activation energies involved in effecting phase changes. In addition, the results of temperature variation of dilatational strain (ΔIT/l0) measured under slow heating scans, are used to obtain reliable estimates of thermal expansion in the temperature range, 300-1000°C.
- Effect of PWHT on the Toughness of Modified 9Cr-1Mo Steel Weldmetal
Authors
1 Indira Gandhi Centre for Atomic Research, Kalpakkam 60310, IN
2 Indira Gandhi Centre for Atomic Research, IN
3 National Institute of Technology, Tiruchirapalli 62001, IN
4 Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, IN
Source
Indian Welding Journal, Vol 47, No 4 (2014), Pagination: 24-24Abstract
Modified 9Cr-1Mo steel is extensively used for high temperature applications due to its good thermo-physical, weldability, fabricability and high temperature properties. While Type IV cracking is of concern during service of weld joints, toughness of its weldmetal is an important consideration during qualification of weld joints, especially for those made by SMAW process. The weldmetal toughness is significantly influenced by deposition process and sequence, and temperature and duration of PWHT. For a special-purpose mod.9Cr-1Mo steel weldmetal, containing intentional addition of 2.4wt% of nickel and manganese, the A and A transformation temperatures, calculated using ThermoCalc software, was found as 945 and 1065K, respectively. To understand its tempering behavior, the weldmetal was subjected to PWHT at 1013, 1033 and 1053K for different durations. The weldmetal hardness decreased significantly on PWHT at 1013K compared to that at 1033 and 1053K. The weldmetal toughness increased monotonically with PWHT temperature; from 27J for 923K PWHT to 32J and 132J for 973K and 1023K PWHTs, respectively, and then decreased marginally to 113J on PWHT at 1153K. These results suggested formation of fresh martensite during PWHT at 1053K. Bright-field transmission electron microscopic examination revealed formation of lath martensite in the weldmetal, with the lath sizes being finer than those reported in other mod. 9Cr-1Mo steel weldmetal prepared using similar process. Hence, detailed microstructural analyses was carried out to investigate this anomalous variation in mechanical properties, as also to study the effect of temperature and duration of PWHT on the microstructure and toughness of this modified 9Cr-1Mo steel weldmetal.- Development and Deployment of Welding Technologies for the Indian Sodium-Cooled Fast Reactor and Advanced Ultra Super Critical Thermal Power Programmes
Authors
1 Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, IN
Source
Indian Welding Journal, Vol 51, No 2 (2018), Pagination: 37-50Abstract
Robust manufacturing technology for Sodium-cooled Fast Reactor (SFR) components necessitates development of various research-backed innovative welding technologies. Prior to the start of construction of the 500 MWe Prototype Fast Breeder Reactor, extensive technology development was planned and implemented for development of welding consumables, procedures and technologies for fabrication of components with stringent specifications. With close interaction amongst design, materials and non-destructive evaluation engineers, materials and welding consumable manufactures, and the fabrication industries, it has been possible to overcome the challenges and establish robust manufacturing technologies for fabrication of all the structural components. Extensive welding is involved in the fabrication of reactor vessels, steam generators, fuel sub-assemblies etc. Further, Activated Tungsten Inert Gas (A-TIG) welding process, along with activated flux developed in-house, has been successfully implemented on various SFR-related components. Also, a computational-intelligence based welding system for online monitoring and control during welding has been developed for obtaining near defect-free welded components. Plasma Transferred Arc Welding process has been deployed for deposition of the chosen nickel-base alloy for hardfacing of SFR components, which require improvement in resistance to high temperature wear, especially galling, of mating surfaces in liquid sodium.
To reduce carbon footprint substantially, India has initiated a national mission programme of design, development and establishment of 800 MWe Advanced Ultra Supercritical (AUSC) power plant having steam parameters of 710°C / 720°C / 310 bar. Materials and fabrication technologies play decisive roles in the success of such mission project. For this purpose, two important India-specific high-temperature tube materials, 304HCu austenitic stainless steel (304HCu SS) and modified Alloy 617M, as also large cylindrical forgings of Alloy 617M of up to 800 mm diameter for turbine rotors have been indigenously developed. Development of welding consumables and welding procedure has also been established for TIG welding of the tubes, including the 304HCu SS/Alloy 617M dissimilar joint. Based on the tensile and creep tests properties, welding consumables for the tubes and their dissimilar joint have been finalized. Technology for dissimilar metal welding between Alloy 617M and 10Cr-steel forgings for turbine rotors has also been developed. Using narrow-gap TIG welding process, the dissimilar metal weld between 200 mm Alloy 617M and 10Cr-steel have been produced by directly welding the two forgings using Alloy 617 filler wire. The weld exhibited no lack-of-penetration defects and passed dye-penetrant, radiographic and ultrasonic examinations. Similarly procedure for NG welding of superheater headers has also been demonstrated.
The details of the Indian efforts towards development and deployment of welding technologies for application to the fabrication to components for the Indian programmes for SFR-based nuclear power and AUSC thermal power plant are presented and discussed.
References
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- Srinivasan G and Bhaduri AK (2007); Development of E316-15 stainless steel electrode for 500 MWe fast breeder reactor, Transactions of the Indian Institute of Metals, 60, pp.399-406.
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- Vasudevan M (2007); Computational and experimental studies on arc welded austenitic stainless steel, PhD thesis submitted to Indian Institute of Technology Madras, Chennai, India.
- Chandrasekhar N, Vasudevan M, Bhaduri AK and Jayakumar T (2012); Proceedings of the 10th International Seminar on Numerical Analysis of Weldability, Graz-Seggau, Austria, SII/P4.
- Vasudevan M, Bhaduri AK and Raj B (2015); A penetration enhancing flux formulation for tungsten inert gas (TIG) welding of austenitic stainless steel and its application, International Patent PCT/IN2006/000442 (2006); Ukraine a 2007 14987 (2007); GB 2446905 (2011); US 8097826 (2012); India 266346 (2015).
- Das CR, Albert SK, Bhaduri AK, Sudha C and Terrance ALE (2005); Characterisation of nickel based hardfacing deposits on austenitic stainless steel, Surface Engineering, 21, pp.290-296.
- Das CR, Ramasubbu V, Albert SK, Bhaduri AK and Balasubramaniam C (2004); Proceedings of International Symposium on Joining of Materials, Welding Research Institute, Tiruchirapalli, India, WME-5.
- Bhaduri AK, Laha K, Albert SK, Jayakumar T and Chetal SC (2015); Development of high temperature boiler tube materials for the Indian advanced ultra super-critical thermal power plant, Proceedings of the 41st MPA-Seminar, Stuttgart, Germany, p.5.
- Dey HC, Albert SK, Srinivasan G, Bhaduri AK and Chetal SC (2017); Dissimilar metal welding of 10Cr steel to Alloy 617M for welded rotor of Advanced Ultra Super Critical (AUSC) thermal power plant, Proceedings of the International Institute of Welding – International Congress on Advances in the Science, Technology and Skill Development in Welding, Indian Institute of Welding, Chennai.
- Welding Processes and Technology for Stainless Steels
Authors
1 Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102, Tamilnadu, IN