Assessment of fatigue crack growth resistance of newly developed LTT alloy composition for the repair of high strength steel structures

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dc.contributor.authorIgwemezie, Victor
dc.contributor.authorMehmanparast, Ali
dc.contributor.authorGanguly, Supriyo
dc.date.accessioned2024-06-19T11:08:36Z
dc.date.available2024-06-19T11:08:36Z
dc.date.issued2024-06-11
dc.description.abstractTensile residual stress (TRS) is a well-known factor that deteriorate the integrity of welded joints. Fatigue failure is accelerated by the existence of TRS introduced during the welding process. There have been efforts in the last two decades to develop filler alloys that can reduce TRS by introducing compressive residual stress (CRS) to oppose the TRS in high strength steel welded joints. These works are based on the theory of austenite (γ) to martensite (α’) transformation and the filler is often called a low transformation-temperature (LTT) alloy. Many studies have reported that the fatigue strength (FS) of weld joint made with LTT alloy is many times better than that of the conventional fillers. It is reported to be particularly useful in the repair of high strength steel structures. However, studies on the fatigue crack growth (FCG) behaviour of these LTT alloys is scarce. In this work, we developed Fe-CrNiMo based LTT weld metal composition, assessed its FCG behaviour and compared the results with that of a conventional welding wire (ER70S-6). It is found that ER70S-6 weld metal obtained under relatively fast cooling is extremely tough, but the associated heat affected zone (HAZ) has poor resistance to FCG which obscured the benefit of the tough weld metal. High heat input or condition that results to slow cooling of the ER70S-6 weldment deteriorates its resistance to FCG. Unfortunately, despite its low martensite start temperature of 231±7 and the anticipated beneficial effect of induced CRS, the LTT alloy studied had the lowest FCG resistance. The LTT alloy appears to have an intrinsic microstructural feature or a ‘fault line’ that reduced its resistance to FCG. While the LTT alloy weld metal has poor resistance to FCG, the associated HAZ resisted FCG more than the HAZ associated with ER70S-6 weld metal. It is observed that aligning the ER70S-6 weld metal perpendicular to the crack front produced the highest resistance to fatigue crack initiation and propagation. In the case of ER70S-6, it is believed that the weld metal induced a CRS at the notch tip which resulted to the high fatigue resistance. In the case of the LTT alloy, perpendicular alignment of the weld metal produced slight improvement.en_UK
dc.description.sponsorshipThis project is funded through EPSRC Doctoral prizeen_UK
dc.identifier.citationIgwemezie V, Mehmanparast A, Ganguly S. (2024) Assessment of fatigue crack growth resistance of newly developed LTT alloy composition for the repair of high strength steel structures. Journal of Advanced Joining Processes, Volume 10, November 2024, Article number 100226en_UK
dc.identifier.eissn2666-3309
dc.identifier.urihttps://doi.org/10.1016/j.jajp.2024.100226
dc.identifier.urihttps://dspace.lib.cranfield.ac.uk/handle/1826/22520
dc.language.isoen_UKen_UK
dc.publisherElsevieren_UK
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 International*
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/*
dc.subjectSteelen_UK
dc.subjectWeldingen_UK
dc.subjectResidual stressen_UK
dc.subjectLTT alloyen_UK
dc.subjectMicrostructureen_UK
dc.subjectMartensiteen_UK
dc.subjectFatigue crack growthen_UK
dc.titleAssessment of fatigue crack growth resistance of newly developed LTT alloy composition for the repair of high strength steel structuresen_UK
dc.typeArticleen_UK

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