Faculty Publications
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Item Evaluation of hydrogen-assisted cracking susceptibility in modified 9cr-1mo steel welds(Springer, 2020) Chakraborty, G.; Rejeesh, R.; Ramana, O.V.; Albert, S.K.The hydrogen-assisted cracking susceptibility of modified 9Cr-1Mo steel weld is evaluated by Y-groove and gapped bead-on-plate test. It is found that a combination of pre + post heat is able to prevent cracking. However, the pre + post heat temperature combination determined from G-BOP test to prevent cracking (200 °C) is found to be higher than that in Y-groove test (100 °C). This is attributed to the higher weld restraint experienced in G-BOP than Y-groove test. For both the tests, the weld metal is found to be more susceptible to cracking than the heat affected zone. In addition to the diffusible hydrogen content of the welding consumables, diffusible hydrogen present in the G-BOP specimens prepared with different preheating and combinations of pre + post heat is also estimated by maintaining identical cooling conditions. The diffusible hydrogen in the weld for which no cracking is reported for G-BOP test (200 °C pre + post heat) is less than 1 ml/100 g. Considering the high restraint conditions present in the G-BOP test, it can be concluded that to prevent HAC in P91 steel, the choice of welding parameters (hydrogen content in welding consumable, heat input, pre/post-heating) should be such that diffusible hydrogen in the weld is brought down to below 1 ml/100 g. © 2019, International Institute of Welding.Item Effect of preheating and post heating in reducing diffusible hydrogen content and hydrogen assisted cracking susceptibility of modified 9Cr–1Mo steel(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Chakraborty, G.; Rejeesh, R.; Zubairuddin, M.; Albert, S.K.The hydrogen assisted cracking susceptibility of Modified 9Cr–1Mo steel weld is evaluated by implant test by determining lower critical stress for different preheating and combination of pre, post heating conditions. The diffusible hydrogen present in the implant specimens for different test conditions is estimated. Residual stress distribution in the weld for different heating condition is estimated using SYSWELD software. For a combination of pre + post heating at 200°C, the diffusible hydrogen content of the weld comes down to 1.17 from 4.7 mL/100g and the lower critical stress of the implant specimen increases from 250 to 370 MPa. Preheating + post heating also brings down the peak tensile residual stress level in the weld joints and lowers the cracking susceptibility. © 2020 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.Item Characterisation of hydrogen assisted cracking in modified 9Cr-1Mo steel welds using acoustic emission non destructive technique(Taylor and Francis Ltd., 2021) Haneef, T.K.; Chakraborty, G.; Rejeesh, R.; Mukhopadhyay, C.K.; Albert, S.K.This study aims a systematic experimental investigation using acoustic emission (AE) non-destructive technique for online monitoring of hydrogen assisted cracking (HAC) in modified 9Cr-1Mo steel (P91 steel) welds during Gap-Bead on Plate (G-BOP) and implant tests. Welds made without preheating, with different preheating and combined pre and post heating were tested using G-BOP test. AE results of G-BOP tests have shown that time duration in which HAC active varies with temperature of preheating and combined pre and post heating. Reduction of AE activity in welds made with pre and post heating compared to those only made with preheating revealed a beneficial effect of the former in reducing HAC. In the case of implant tests, crack initiation and propagation are identified for different applied loads from the AE analysis. An attempt has been made to compare HAC during G-BOP tests and implant tests using AE frequency analysis. The dominant frequency of AE signals characteristic of HAC has been identified. This study shows the potential of using AE frequency analysis for online monitoring of hydrogen assisted cracking (HAC) in welds. © 2021 Informa UK Limited, trading as Taylor & Francis Group.