A comparative study on the effect of GTAW processes on the microstructure and mechanical properties of P91 steel weld joints |
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| Institution: | 1. Government Engineering College, Surat, Gujarat, India;2. Mechanical Engineering Department, S.V. National Institute of Technology, Surat, Gujarat, India;1. Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India;2. Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India;3. National Metallurgical Laboratory, Jamshedpur 831007, India;4. Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India;1. Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee, 247667, India;2. Mechanical Department, Indian Institute of Technology Jodhpur, Rajasthan, 342037, India;3. Mechanical Engineering Department, Indian Institute of Technology Bhubaneswar, Odisha, 752050, India;1. Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 807, Taiwan, ROC;2. Metal Industries Research & Development Centre, 1001 Kaonan Highway, Kaohsiung 811, Taiwan, ROC;1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, Buenos Aires, C1033AAJ, Argentina;2. Comisión Nacional de Energía Atómica, CAC-Gerencia Materiales, Av. Gral. Paz 1499, San Martín (Buenos Aires), B1650KNA, Argentina |
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| Abstract: | Modified 9Cr-1Mo (P91) steel is widely used in the construction of power plant components. In the present study, a comparative study on influence of activated flux tungsten inert gas (A-TIG), and gas tungsten arc (GTA) welding processes on the microstructure and the impact toughness of P91 steel welds was carried out. P91 steel welds require a minimum of 47 J during the hydrotesting of vessels as per the EN1557: 1997 specification. Toughness of P91 steel welds was found to be low in the as-weld condition. Hence post-weld heat treatment (PWHT) was carried out on weld with the objective of improving the toughness of weldments. Initially as per industrial practice, PWHT at 760 °C – 2 h was carried out in order to improve the toughness of welds. It has been found that after PWHT at 760 °C – 2 h, GTA weld (132 J) has higher toughness than the required toughness (47 J) as compared with A-TIG weld (20 J). The GTA weld has higher toughness due to enhanced tempering effects due to multipass welding, few microinclusion content and absence of δ-ferrite. The A-TIG weld requires prolonged PWHT (i.e. more than 2 h at 760 °C) than GTA weld to meet the required toughness of 47 J. This is due to harder martensite, few welding passes that introduces less tempering effects, presence of δ-ferrite (0.5%), and more alloy content. After PWHT at 760 °C – 3 h, the toughness of A-TIG weld was improved and higher than the required toughness of 47 J. |
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| Keywords: | P91 steel δ-Ferrite Welding Toughness |
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