Factors Distinguishing Hydrogen-Assisted Intergranular and Intergranular-Like Fractures in a Tempered Lath Martensitic Steel

Chen, Tingshu; Chiba, Takahiro; Koyama, Motomichi; Akiyama, Eiji; Takai, Kenichi

doi:10.1007/s11661-022-06608-2

Cited by 24 publications

(3 citation statements)

References 52 publications

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“…Shibata et al 31) reported that hydrogen-induced IG crack propagation was microscopically followed by crack blunting due to plastic deformation and discontinuous propagation of subcrack formations away from the crack tip, leading to macroscopically stable fracture. Koyama et al 32) observed some plasticity-related IG fracture cracks in detail and reported that the cracks on the prior B grain boundaries were discontinuous and that nanovoid linkages formed tear ridges on the grain boundaries. Chiba et al 5 prepared full intergranular fracture surfaces of tempered martensitic steel charged with hydrogen and analyzed the lattice defects using low-As shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen Content Dependence of Crack Initiation and Propagation Behavior of Hydrogen Embrittlement in Tempered Martensitic Steel

Uemura,

Chiba,

Saito

et al. 2024

ISIJ Int.

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Crack initiation and propagation behavior in hydrogen embrittlement fracture of tempered martensitic steel at a low hydrogen content was compared with the results at a high hydrogen content. Notched specimens charged with a low hydrogen content of 0.18 ppm and a high hydrogen content of 5.3 ppm were stressed and unloaded immediately upon reaching the maximum stress in tensile tests. At the low hydrogen content, quasi-cleavage (QC) fracture was dominant at the notch tip, and mixed intergranular (IG) and QC fractures were observed away from the notch tip. A crack initiated in the prior B grains at the notch tip and propagated along the {011} plane.The crack initiation site corresponded to the site of maximum equivalent plastic strain. The other crack initiating on the prior B grain boundaries was observed at a site away from the notch tip. Microvoids were formed discontinuously inclined at about 45° to the tensile axis direction between these two types of cracks observed at the low hydrogen content. In contrast, at the high hydrogen content, cracks initiated on the prior B grain boundaries away from the notch tip. The crack initiation site corresponded to the vicinity of the region where both the principal stress and hydrogen concentration were high. These findings indicate that crack initiation at the low hydrogen content is not necessarily consistent with the site of the maximum principal stress and the local hydrogen concentration, unlike the case of the high hydrogen content.

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Section: Discussionmentioning

confidence: 99%

Hydrogen Content Dependence of Crack Initiation and Propagation Behavior of Hydrogen Embrittlement in Tempered Martensitic Steel

Uemura,

Chiba,

Saito

et al. 2024

ISIJ Int.

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“…However, hydrogen embrittlement susceptibility increases with increasing strength of steels, and a lathmartensitic steel is particularly susceptible to hydrogen embrittlement [1][2][3][4][5] . Typical fracture morphologies are intergranular (IG) fracture along prior austenite (γ) grain boundaries [6][7][8][9] and quasi-cleavage (QC) fracture [9][10][11][12][13][14][15][16] that occurs along the block/lath boundary or {011} slip plane of the body-centered cubic lattice, and each fracture mechanism may be different. The most important issue is to identify the crack initiation sites and clarify the main factor involved in order to elucidate the mechanism of each fracture mode.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Crack Initiation Sites and Main Factors Causing Hydrogen Embrittlement of Tempered Martensitic Steels with Different Carbide Precipitation States

2024

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The dependence of crack initiation sites and main factors causing hydrogen embrittlement fracture on carbide precipitation states has been investigated for tempered martensitic steels with the same tensile strength of 1450 MPa. Notched specimens charged with hydrogen were stressed until just before fracture and subsequently unloaded. The crack initiation site exhibited intergranular (IG) fracture at 21 m ahead of the notch tip as observed by scanning electron microscopy (SEM) for 0.28% Si specimens with plate-like carbide precipitates on prior austenite () grain boundaries. This crack initiation site corresponded to the vicinity of the maximum principal stress position as analyzed by a finite element method (FEM). The initiation site corresponded to the triple junction of prior  grain boundaries as analyzed by electron backscattered diffraction (EBSD). In contrast, the crack initiation site exhibited quasi-cleavage (QC) fracture at the notch tip for 1.88% Si specimens with fine and thin carbide particles in the grains. This crack initiation site corresponded to the maximum equivalent plastic strain site obtained by FEM. Additionally, the crack initiated on the inside of prior  grain boundaries and propagated along the {011} slip plane with higher kernel average misorientation (KAM) values as analyzed by EBSD. These findings indicate that differences in carbide precipitation states changed the crack initiation sites and fracture morphologies involved in hydrogen embrittlement depending on mechanical factors such as stress and strain and microstructural factors.

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“…The origin and underlying mechanisms responsible for the H-induced IG and QC fractures are also continuing the critical interests of researchers, proposing some key mechanisms in terms of grain boundary (GB) decohesion by segregated hydrogen atoms [23][24][25] , nano-scale void nucleation along GBs [26][27][28] , and local enhancement of dislocations activity ahead of the crack tip 12,29,30) . On the other hand, little attention has been placed on the HA-FCG property and accompanying fracture morphologies of pearlite 5,11,19,22) , a commonly contained microstructure in the various commercially available BCC steels.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Propagation in Pearlitic Steel under Pressurized Gaseous Hydrogen: Influences of Microstructure Size and Strength Level

Ogawa

Iwata

2023

ISIJ Int.

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For the wall-thickness reduction of the components destined for pressurized gaseous hydrogen, widespread use of high-strength martensitic steels has long been desired. However, their strong susceptibility to hydrogen-assisted fatigue crack growth (HA-FCG) is still limiting their proactive applications. Here, we instead focused on pearlite as another potential reinforcing agent for the development of new hydrogen-compatible steels with acceptable cost performance. Fatigue crack growth (FCG) behavior of three eutectoid steels with different microstructure sizes (i.e., ferrite/cementite interlamellar spacing, colony and block sizes) and strength levels was investigated in a 90 MPa hydrogen gas, an essential evaluation when attempting to perform a defect tolerant design of the components used for high-pressure gases.The pearlitic steels clearly exhibited the acceleration of their FCG rate in hydrogen gas up to a hundred times that in air, wherein its magnitude was greater in the material with finer microstructure and concomitant higher strength. The delamination of ferrite/cementite lamellae, which were inclined largely from the loading axis, was determined to be the primary cause of such HA-FCG in pearlitic steels. Nevertheless, the extent of FCG acceleration was minor with respect to martensitic steels. The fact was ascribed to the barrier role of the cementite platelets oriented nearly perpendicularly to the crack as well as to the geometrical retardation effects arising from the crack deflection and blanching.Ultimately, pearlite was superior to martensite from the perspective of HA-FCG resistance; besides, the superiority was more substantial as the loading rate became slower.

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Factors Distinguishing Hydrogen-Assisted Intergranular and Intergranular-Like Fractures in a Tempered Lath Martensitic Steel

Cited by 24 publications

References 52 publications

Hydrogen Content Dependence of Crack Initiation and Propagation Behavior of Hydrogen Embrittlement in Tempered Martensitic Steel

Hydrogen Content Dependence of Crack Initiation and Propagation Behavior of Hydrogen Embrittlement in Tempered Martensitic Steel

Comparison of Crack Initiation Sites and Main Factors Causing Hydrogen Embrittlement of Tempered Martensitic Steels with Different Carbide Precipitation States

Fatigue Crack Propagation in Pearlitic Steel under Pressurized Gaseous Hydrogen: Influences of Microstructure Size and Strength Level

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