Insight into Type IV cracking in Grade 91 steel weldments

Wang, Yiyu; Kannan, Rangasayee; Li, Leijun

doi:10.1016/j.matdes.2020.108570

Cited by 43 publications

(17 citation statements)

References 34 publications

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“…The Xe + PFIB-DIC technique can also map time-resolved HR microscale strain relaxation, which provides insight into analyzing the void formation and creep cracking caused by residual stress relief. It has been widely reported that the creep cracks are a crucial challenge for ferritic-martensitic steels under load at high temperature, and residual stress is often considered as the most primary reason for microcracking ( 45 , 46 ). The high operating temperature triggers the thermal relaxation of welding-induced residual stress.…”

Section: Discussionmentioning

confidence: 99%

A novel pathway for multiscale high-resolution time-resolved residual stress evaluation of laser-welded Eurofer97

et al. 2022

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The plasma-facing components of future fusion reactors, where the Eurofer97 is the primary structural material, will be assembled by laser-welding techniques. The heterogeneous residual stress induced by welding can interact with the microstructure, resulting in a degradation of mechanical properties and a reduction in joint lifetime. Here, a Xe + plasma focused ion beam with digital image correlation (PFIB-DIC) and nanoindentation is used to reveal the mechanistic connection between residual stress, microstructure, and microhardness. This study is the first to use the PFIB-DIC to evaluate the time-resolved multiscale residual stress at a length scale of tens of micrometers for laser-welded Eurofer97. A nonequilibrium microscale residual stress is observed, which contributes to the macroscale residual stress. The microhardness is similar for the fusion zone and heat-affected zone (HAZ), although the HAZ exhibits around ~30% tensile residual stress softening. The results provide insight into maintaining structural integrity for this critical engineering challenge.

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Section: Discussionmentioning

confidence: 99%

A novel pathway for multiscale high-resolution time-resolved residual stress evaluation of laser-welded Eurofer97

et al. 2022

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“…The precipitation of the Laves phase is considered to be the main cause of Type IV cracking in 9-12% Cr steel because the nucleation and growth of the Laves phase promote diffusion of W or Mo from the matrix to the Laves phase, which results in the loss of solid solution strengthening and deteriorates the creep properties. When the Laves phase precipitates on the grain boundaries, the sliding of grain boundary during creep could lead to stress-strain concentration at the Laves phase/matrix interface, which results in the nucleation and growth of the creep void [10][11][12]19,32,37].…”

Section: Type IV Failure Mechanism In the Ichazmentioning

confidence: 99%

Effect of Postweld Heat Treatments on Type IV Creep Failure in the Intercritical Heat-Affected Zone of 10% Cr Martensitic Steel Welded with Haynes 282 Filler

Kim

Kang

Bang

et al. 2021

Metals

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This study investigated the effect of postweld heat treatment (PWHT) conditions on Type IV failure behavior of 10% Cr martensitic steel welds using Haynes 282 filler. The welded joints were subjected to PWHT at temperatures of 688, 738, and 788 °C for 4 and 8 h. Creep tests were carried out at 600 °C under a stress of 200 MPa. The as-welded joint without PWHT showed Type IV cracking due to growth of voids around Laves phase by localized creep deformation in the intercritical heat-affected zone (ICHAZ). The creep properties of the PWHTed joints at 688 °C were similar to those of the as-welded joints without PWHT. On the other hand, the PWHTed joints at 738 °C exhibited a significantly longer creep life by a lower amount of Laves phase in the ICHAZ than those at 688 °C; this could be a result of the homogenization of ICHAZ microstructure during PWHT at 738 °C. However, the PWHT at 688 and 738 °C showed the same Type IV creep failure mode. Meanwhile, the PWHTed joints at 788 °C exhibited the shortest creep life in this study. The failure location was shifted to the base metal away from the HAZ, and severe plastic deformation occurred due to the softened matrix by excessive tempering.

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“…Generally, the microstructure has three main regions: Fusion Zone (FZ), Heat Affected Zone (HAZ), and Base Metal (the substrate where deposition occurs). FZ is characterized by the liquid phase mixture (dilution) of the filler metal and the base metal and is generally geometrically characterized by three important parameters: reinforcement, width and depth [ 7 , 8 ]. The study conducted by [ 8 ] evaluated the premature Type IV cracking to clarify its mechanisms in Grade 91 steel pipe weldments using ER90S-B9 and E91T1-B9 wires.…”

Section: Introductionmentioning

confidence: 99%

“…FZ is characterized by the liquid phase mixture (dilution) of the filler metal and the base metal and is generally geometrically characterized by three important parameters: reinforcement, width and depth [ 7 , 8 ]. The study conducted by [ 8 ] evaluated the premature Type IV cracking to clarify its mechanisms in Grade 91 steel pipe weldments using ER90S-B9 and E91T1-B9 wires. The authors observed that FZ is the region in the welded joint that presents higher strain level and hardness, lowest creep and finest grain size (martensite laths).…”

Section: Introductionmentioning

confidence: 99%

Mild Steel GMA Welds Microstructural Analysis and Estimation Using Sensor Fusion and Neural Network Modeling

Caio

Silva

Bestard

et al. 2021

Sensors

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This study aims at evaluating the efficiency of sensor fusion, based on neural networks, to estimate the microstructural characteristics of both the weld bead and base material in GMAW processes. The weld beads of AWS ER70S-6 wire were deposited on SAE 1020 steel plates varying welding voltage, welding speed, and wire-feed speed. The thermal behavior of the material during the process execution was analyzed using thermographic information gathered by an infrared camera. The microstructure was characterized by optical (confocal) microscopy, scanning electron microscopy, and X-ray Diffraction tests. Finally, models for estimating the weld bead microstructure were developed by fusing all the information through a neural network modeling approach. A R value of 0.99472 was observed for modelling all zones of microstructure in the same ANN using Bayesian Regularization with 17 and 15 neurons in the first and second hidden layers, respectively, with 4 training runs (which was the lowest R value among all tested configurations). The results obtained prove that RNAs can be used to assist the project of welded joints as they make it possible to estimate the extension of HAZ.

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Insight into Type IV cracking in Grade 91 steel weldments

Cited by 43 publications

References 34 publications

A novel pathway for multiscale high-resolution time-resolved residual stress evaluation of laser-welded Eurofer97

A novel pathway for multiscale high-resolution time-resolved residual stress evaluation of laser-welded Eurofer97

Effect of Postweld Heat Treatments on Type IV Creep Failure in the Intercritical Heat-Affected Zone of 10% Cr Martensitic Steel Welded with Haynes 282 Filler

Mild Steel GMA Welds Microstructural Analysis and Estimation Using Sensor Fusion and Neural Network Modeling

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