The effects of postweld heat treatment and isothermal aging on T92 steel heat-affected zone mechanical properties of T92/TP316H dissimilar weldments

Falat, Ladislav; Kepič, Ján; Čiripová, Lucia; Ševc, Peter; Dlouhý, Ivo

doi:10.1557/jmr.2016.134

Cited by 19 publications

(19 citation statements)

References 34 publications

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“…• C. The microstructure of P/T92 base material is typically formed of tempered lath martensite with finely dispersed intragranular MX (M = V, Nb; X = C, N) carbonitrides and intergranular M 23 C 6 (M = Cr, Fe) carbides at grain, block, and lath boundaries [17][18][19][20][21]. The most significant microstructural change in Grade 92 steels during their long-term ageing and/or creep exposure is the additional precipitation of intermetallic Fe 2 (W, Mo) based Laves phase, typically in the vicinity of M 23 C 6 carbides [19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

Falat¹,

Čiripová²,

Homolová³

et al. 2016

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The effects of thermal exposure at 600• C and subsequent electrolytic hydrogen charging at ambient temperature were studied in terms of their influence on notch-tensile properties and fracture behaviour of individual heat-affected zones (HAZ) of Ni-based transition weldments between T24 and T92 creep-resistant steels. The experimental welded joints were prepared by gas tungsten arc welding using "Inconel-type" filler metal Nirod 600. Post-weld heat treatment (PWHT) was carried out at 720• C for 2 h, followed by passive cooling within tempering furnace. Subsequent long-term ageing of two series of prepared T24/T92 dissimilar welds at 600• C for 1000 and 5000 h, respectively, led to gradual changes in both T24 and T92 HAZ microstructures, which were mainly related to their additional tempering accompanied by the coarsening of original precipitates as well as newly-formed secondary phases. The observed thermally-induced microstructural changes together with subsequently applied hydrogen charging effects resulted in complex variations in tensile properties and fracture behaviour of individual HAZ regions related to the pre-existing differences in their initial tempering grade due to the used PWHT procedure. K e y w o r d s : creep-resistant steels, dissimilar welding, isothermal ageing, hydrogen embrittlement, mechanical properties, fracture mechanisms

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Section: Introductionmentioning

confidence: 99%

“…The most significant microstructural change in Grade 92 steels during their long-term ageing and/or creep exposure is the additional precipitation of intermetallic Fe 2 (W, Mo) based Laves phase, typically in the vicinity of M 23 C 6 carbides [19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

Falat¹,

Čiripová²,

Homolová³

et al. 2016

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“…In general, the HAZ region with its strongly heterogeneous microstructure, so-called "HAZ microstructural gradient", is considered to be the critical region of welded joints because of its high propensity for several types of cracking and final failure occurrence [9,10]. The findings of our several former studies about dissimilar T92/TP316H weldments [11][12][13][14] have clearly indicated that the HAZ microstructural heterogeneity can be efficiently suppressed by the application of unconventional "quenching-and-tempering" post-welding heat treatment (QT PWHT). In contrast to microstructural characteristics obtained after conventional "tempering" PWHT (T PWHT), the microstructures of welded base materials after performing QT PWHT became coarser and homogenized with respect to the grain size and state of secondary phase precipitation.…”

Section: Introductionmentioning

confidence: 90%

The Effects of Electrochemical Hydrogen Charging on Room-Temperature Tensile Properties of T92/TP316H Dissimilar Weldments in Quenched-and-Tempered and Thermally-Aged Conditions

Ševc

Falat

Čiripová

et al. 2019

Metals

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The influence of isothermal aging at 620 °C in combination with subsequent electrochemical hydrogen charging at room-temperature was studied on quenched-and-tempered T92/TP316H martensitic/austenitic weldments in terms of their room-temperature tensile properties and fracture behavior. Hydrogen charging of the weldments did not significantly affect their strength properties; however, it resulted in considerable deterioration of their plastic properties along with significant impact on their fracture characteristics and failure localization. The hydrogen embrittlement plays a dominant role in degradation of the plastic properties of the weldments already in their initial material state, i.e., before thermal aging. After thermal aging and subsequent hydrogen charging, mutual superposition of thermal and hydrogen embrittlement phenomena had led to clearly observable effects on the welds deformation and fracture processes. The measure of hydrogen embrittlement was clearly lowered for thermally aged material state, since the contribution of thermal embrittlement to overall degradation of the weldments has dominated. The majority of failures of the weldments after hydrogen charging occurred in the vicinity of T92 BM/Ni weld metal (WM) fusion zone; mostly along the Type-II boundary in Ni-based weld metal. Thus, regardless of aging exposure, the most critical failure regions of the investigated weldments after hydrogen charging and tensile straining at room temperature are the T92 BM/Ni WM fusion boundary and Type-II boundary acting like preferential microstructural sites for hydrogen embrittling effects accumulation.

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“…Due to the presence of microstructural gradient and welding-related residual stresses in welded joints of martensitic/ferritic power plant steel, it is necessary to perform their postweld heat treatment (PWHT). Beside thermal stabilization of initial weld microstructure and residual stress relief, the application of PWHT decreases unallowably high hardness in FZ and increases the weldments toughness [2,5,6]. Worldwide constant efforts are still being put into developments aiming for creep strength improvement of these materials.…”

Section: Introductionmentioning

confidence: 99%

Ageing Effects on Microstructure, Mechanical Properties, and Fracture Behaviour of 9Cr-1.5Mo-1Co-VNbBN Martensitic Steel Welded Joint for High Temperature Application

Falat¹,

Homolová²,

Čiripová³

et al. 2017

Advances in Materials Science and Engineering

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This paper deals with long-term ageing effects of 9Cr-1.5Mo-1Co-VNbBN (CB2) steel weldment on its impact toughness, creep rupture behaviour, and hardness in relation to microstructure and fracture characteristics. The weldment was studied in PWHT state and after isothermal expositions at 625 ∘ C for 10000 and 30000 hours. Microstructure evolution was studied using analytical scanning and transmission electron microscopy. Charpy V-notch impact toughness tests were performed for all heat-treated states with a notch location in distinct weld regions such as weld metal (WM), heat-affected zone (HAZ), and base material (BM). The overheated HAZ region exhibited the lowest impact toughness as a result of severe welding induced microstructure degradation. Creep tests were performed at 625 ∘ C in the stress range between 80 and 120 MPa. At the highest applied stress, creep fracture occurred in WM, whereas at lower stresses the failure position shifted towards fusion zone at WM/HAZ interface. The hardness profiles experienced significant scattering due to weld microstructural heterogeneity. The major fracture mechanisms involved transgranular quasi cleavage and intergranular creep cracking in impact and creep loading conditions, respectively.

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The effects of postweld heat treatment and isothermal aging on T92 steel heat-affected zone mechanical properties of T92/TP316H dissimilar weldments

Abstract: Abstract

Cited by 19 publications

References 34 publications

Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

The Effects of Electrochemical Hydrogen Charging on Room-Temperature Tensile Properties of T92/TP316H Dissimilar Weldments in Quenched-and-Tempered and Thermally-Aged Conditions

Ageing Effects on Microstructure, Mechanical Properties, and Fracture Behaviour of 9Cr-1.5Mo-1Co-VNbBN Martensitic Steel Welded Joint for High Temperature Application

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