Effect of Nb–Ti multi-microalloying on the hydrogen trapping efficiency and hydrogen embrittlement susceptibility of hot-stamped boron steel

Zhang, Shiqi; Liu, Shilong; Wan, Jifang; Liu, Wei

doi:10.1016/j.msea.2019.138788

Cited by 31 publications

(12 citation statements)

References 41 publications

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“…The negligible effect of Nb compositions shown in Nb0-B and Nb2-B steels may appear inconsistent with previous studies, which have considered a hydrogen trapping by Nb carbides as the primary factor for HE resistance of TM steels 14 , 17 . The hydrogen trapping by Nb carbides has been experimentally proven by various methods, such as TDA 18 and small-angle neutron scattering 19 .…”

Section: Resultscontrasting

confidence: 82%

“…This is in good accord with previous studies 3, 5 . The primary hydrogen-trapping sites in TM steel are high-angle boundaries of PAG, packets, blocks, and laths as well as precipitates 13,14 . According to a recent study of Zhang et al 5 , the Nb addition to a martensitic steel rarely changes the total amount of hydrogen trapped by these boundaries, although the local hydrogen concentration significantly varied depending on the boundary type.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Effect of undissolved Nb carbides on mechanical properties of hydrogen-precharged tempered martensitic steel

Seo

Kim

et al. 2020

Sci Rep

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Nb carbides have attracted significant attention to enhance the resistance of tempered martensitic (TM) steel to hydrogen embrittlement (HE). However, previous studies have elucidated the role of Nb carbides in HE resistance without categorizing their types (i.e., undissolved and newly precipitated). This study focuses on the effect of "undissolved" Nb carbides on the tensile and fatigue properties of hydrogen-precharged TM steels. It validated the following two factors for the HE resistance of the TM steels containing undissolved Nb carbides: hydrogen-trapping by the carbides and refinement of prior austenite grain. The former factor rarely affected the HE resistance owing to the interfacial incoherency between the undissolved carbides and ferritic matrix. Such results are distinguished from previous studies focusing on the newly precipitated carbides. In contrast, the latter factor contributed significantly to the HE resistance via the decrease in hydrogen contents per unit surface of prior austenite grain boundaries. Hydrogen embrittlement (HE) indicates the deterioration in mechanical properties owing to hydrogen atoms inside a ferrous alloy 1,2. HE is particularly important for the use of high-strength steels, such as a tempered martensitic (TM) steel. The TM structure can yield a high strength that exceeds 1.2 GPa after a simple heat treatment, rendering this steel important for various industries. Nevertheless, a high density of defects in the TM structure renders it highly vulnerable to HE 3. Consequently, this has resulted in increasing demands for an enhanced HE resistance of TM steels. The addition of Nb is an effective approach to increase the HE resistance of TM steels. It has been reported that HE resistance increases owing to the hydrogen trapping by Nb carbides and the refinement of prior austenite grains (PAGs). Such factors hindered the diffusion and concentration of the hydrogen present inside materials 4. A recent study 5 suggested a different mechanism for achieving an improvement in HE resistance, wherein Nb addition decreased the Σ3 boundary fraction in lath martensites. However, previous studies have primarily investigated Nb carbides, which are newly precipitated during a tempering process. The other type of Nb carbides (i.e., "undissolved" carbides) has attracted significantly less attention despite the fact that their resultant amounts are not negligibly small. Therefore, the effect of undissolved Nb carbides on the HE resistance of TM steels was investigated in this study. Four hydrogen-precharged TM steels were evaluated under uniaxial and cyclic loading conditions by considering the application environment of the material.

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Section: Resultscontrasting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

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Effect of undissolved Nb carbides on mechanical properties of hydrogen-precharged tempered martensitic steel

Seo

Kim

et al. 2020

Sci Rep

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“…[5][6][7] Concerning the alloy design, decreasing C and Mn and adding micro-alloy elements such as Nb, Ti, Mo have been reported to increase the resistance to delayed fracture. [8][9][10][11][12][13][14][15] In a conventional hot stamping process, steel sheets are heated to around 900°C and held for about 5 min in a furnace. In the usual case, nitrogen gas with a low dew point as a furnace atmosphere is used in order to avoid scale formation and surface decarburization as much as possible.…”

Section: Decarburizing Behavior and Its Effect On Mechanical Properties Of Ultrahigh Strength Steel Sheetsmentioning

confidence: 99%

Decarburizing Behavior and Its Effect on Mechanical Properties of Ultrahigh Strength Steel Sheets

et al. 2021

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“…In the first commercialized 34MnB5 PHS, combined microalloying of niobium and molybdenum contributes to microstructural refinement and shows benefits for reducing susceptibility to HE (Uranga et al, 2020;Mohrbacher and Senuma, 2020). Actually, many studies have shown that nanocarbides can enhance the resistance to HE (Zhang et al, 2011;Kim et al, 2018;Zhang et al, 2015;Zhang et al, 2020;Lin et al, 2018). In addition, many studies have investigated HE in PHSs with surface coatings, which could increase the take-up of hydrogen and retard the escape of hydrogen (Georges et al, 2013;Cho et al, 2018b;Jo et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Role of Vanadium Carbide in Hydrogen Embrittlement of Press-Hardened Steels: Strategy From 1500 to 2000 MPa

Lin

Chang

et al. 2021

Front. Mater.

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This work investigated hydrogen trapping and hydrogen embrittlement (HE) in two press-hardened steels, 22MnB5 for 1,500 MPa grade and 34MnB5V for 2000 MPa grade, respectively. Superior to the 22MnB5 steel, the newly developed 34MnB5V steel has an ultimate tensile strength of over 2000 MPa without sacrificing ductility due to the formation of vanadium carbides (VCs). Simulated press hardening was applied to two steels, and hydrogen was induced by cathodic charging. Susceptibility to HE was validated by slow strain-rate tensile test. When hydrogen content was high, the 34MnB5V steel fractured in elastic regime. However, when hydrogen content was 0.8–1.0 ppmw, the 34MnB5V steel bore much higher stress than the 22MnB5 steel before fracture. The behavior of hydrogen trapping was investigated by thermal desorption analyses. Although the two steels trapped similar amounts of hydrogen after cathodic charging, their trapping mechanisms and effective trapping sites were different. In summary, a finer prior austenite grain size due to the pinning effect of VCs can also improve the toughness of 34MnB5V steel. Moreover, trapping hydrogen by grain boundary suppresses the occurrence of hydrogen-enhanced local plasticity. Microstructural refinement enhanced by VCs improves the resistance to HE in 34MnB5V steel. Importantly, the correlation between hydrogen trapping by VCs and improvement of HE is not significant. Hence, this work presents the challenge in designing irreversible trapping sites in future press-hardened steels.

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Effect of Nb–Ti multi-microalloying on the hydrogen trapping efficiency and hydrogen embrittlement susceptibility of hot-stamped boron steel

Cited by 31 publications

References 41 publications

Effect of undissolved Nb carbides on mechanical properties of hydrogen-precharged tempered martensitic steel

Effect of undissolved Nb carbides on mechanical properties of hydrogen-precharged tempered martensitic steel

Decarburizing Behavior and Its Effect on Mechanical Properties of Ultrahigh Strength Steel Sheets

Role of Vanadium Carbide in Hydrogen Embrittlement of Press-Hardened Steels: Strategy From 1500 to 2000 MPa

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