Hydrogen Transport in 34CrMo4 Martensitic Steel: Influence of Microstructural Defects on H Diffusion

The electrochemical permeation technique was used to evaluate the effect of the microstructure on hydrogen diffusivity and hydrogen trapping at room temperature in martensitic steels. A detailed study of the electrochemical permeation technique was first performed in order to identify the boundary conditions of a permeation test in the selected experimental set-up. The validity of the apparent diffusion coefficient derived from this test is also discussed. A 34CrMo4 quenched steel has been selected and designed at three tempering temperatures (200°C, 540°C and 680°C) in order to obtain three different microstructures. According to permeation measurements, H diffusion strongly depends on the microstructure. The material tempered at 540°C exhibits the smallest diffusion coefficient and the largest fraction of reversible traps at room temperature.

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Hydrogen Trapping Behavior in Vanadium Microalloyed TRIP-Assisted Annealed Martensitic Steel

Metals ◽

10.3390/met9070741 ◽

2019 ◽

Vol 9 (7) ◽

pp. 741

Author(s):

Yang ◽

Yu ◽

Keyword(s):

Vanadium Carbide ◽

Hydrogen Diffusion ◽

Martensitic Steel ◽

Tensile Tests ◽

Test Results ◽

Hydrogen Trapping ◽

Martensitic Steels ◽

Transformation Induced Plasticity ◽

Hydrogen Charging ◽

Transmission Electron

Transformation induced plasticity (TRIP)-assisted annealed martensitic (TAM) steel combines higher tensile strength and elogangtion, and has been increasingly used but appears to bemore prone to hydrogen embrittlement (HE). In this paper, the hydrogen trapping behavior and HE of TRIP-assisted annealed martensitic steels with different vanadium additions had been investigated by means of hydrogen charging and slow strain rate tensile tests (SSRT), microstructral observartion, and thermal desorption mass spectroscope (TDS). Hydrogen charging test results indicates that apparent hydrogen diffusive index Da is 1.94 × 10−7/cm2·s−1 for 0.21wt.% vanadium steel, while the value is 8.05×10−7/cm2·s−1 for V-free steel. SSRT results show that the hydrogen induced ductility loss ID is 76.2% for 0.21wt.%V steel, compared with 86.5% for V-free steel. The trapping mechanism of the steel containing different V contents is analyzed by means of TDS and Transmission electron microscope (TEM) observations. It is found out that the steel containing 0.21wt.%V can create much more traps for hydrogen trapping compared with lower V steel, which is due to vanadium carbide (VC) precipitates acting as traps capturing hydrogen atoms.The relationship between hydrogen diffusion and hydrogentrapping mechanism is discussed in details.

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Role of Mo/V carbides in hydrogen embrittlement of tempered martensitic steel

Corrosion Reviews ◽

10.1515/corrrev-2015-0052 ◽

2015 ◽

Vol 33 (6) ◽

pp. 433-441 ◽

Cited By ~ 18

Author(s):

Junmo Lee ◽

Taekyung Lee ◽

Young Jin Kwon ◽

Dong-Jun Mun ◽

Jang-Yong Yoo ◽

...

Keyword(s):

Chemical Composition ◽

Hydrogen Embrittlement ◽

Beneficial Effect ◽

Mechanical Performance ◽

Martensitic Steel ◽

Carbide Precipitation ◽

Hydrogen Trapping ◽

Martensitic Steels ◽

Cr Addition

AbstractThe vulnerability of tempered martensitic steel to hydrogen embrittlement (HE) has attracted attention from a number of researchers. Although utilizing carbide precipitation is one of effective methods to improve HE resistance, few studies have focused on the effects of carbide characteristics, such as the chemical composition and morphology of carbide. This work clarifies the role of Mo carbide and V carbide in the HE behavior of tempered martensitic steels with four steels whose chemical composition was carefully controlled. The beneficial effect of carbides is discussed in terms of hydrogen trapping and fracture mode. The low amount of trapped hydrogen and undissolved carbide led to excellent HE resistance of Mo carbides compared to V carbides. In addition, the superior mechanical performance of Cr-Mo steel was also interpreted by the effect of Cr addition as well as Mo carbides.

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Hydrogen Trap on the Microstructure of Cr-Mo Type Steels

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.283-286.370 ◽

2009 ◽

Vol 283-286 ◽

pp. 370-375 ◽

Cited By ~ 3

Author(s):

L.F. Lemus ◽

Janyne H. Rodrigues ◽

D.S. Santos ◽

L.H. Almeida

Keyword(s):

Hydrogen Trapping ◽

Hydrogen Diffusivity ◽

Transmission Electron Microscopy Analysis ◽

Hydrogen Trap ◽

Thermal Desorption Spectrometry ◽

Transmission Electron ◽

Bainitic Microstructure ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

Permeation Test

Microstructure influence on hydrogen trapping in a Cr-Mo type steels −2.25Cr 1Mo and 2.25Cr 1Mo 0.25V− was studied by means of electrochemical permeation test, thermal desorption spectrometry, scanning and transmission electron microscopy analysis. Both steels, used in hydrogenation reactors, in as received and artificial aged conditions exhibit a bainitic microstructure with CrxMoy and CrxMoyVz carbides finely dispersed. The hydrogen diffusivity for the 2.25Cr-1Mo-0.25V is lower than 2.25Cr-1Mo due to its higher carbide precipitation. At aged conditions TDS on samples cathodically charged with hydrogen showed an increase on the hydrogen trapping capacity for 2.25Cr-1Mo and a reduction for the vanadium modified steel, compared with the as-received state.

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Observations on the Relationship between Crystal Orientation and the Level of Auto-Tempering in an As-Quenched Martensitic Steel

Metals ◽

10.3390/met9121255 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1255 ◽

Cited By ~ 4

Author(s):

Shashank Ramesh Babu ◽

Tuomo Nyyssönen ◽

Matias Jaskari ◽

Antti Järvenpää ◽

Thomas Paul Davis ◽

...

Keyword(s):

Room Temperature ◽

Martensitic Steel ◽

Low Carbon ◽

Martensitic Steels ◽

Tempered Martensite ◽

Martensitic Microstructure ◽

Austenite Grains ◽

Variant Analysis ◽

The Relationship ◽

Electron Back Scattered Diffraction

Auto-tempering is a feature of the technologically important as-quenched low-carbon martensitic steels. The focus of this paper is on the morphology of the martensite and the orientation of the last forming untempered regions in relation to the earlier formed auto-tempered martensite in both small and large austenite grains. A low-carbon martensitic steel plate was austenitized for 24 h and quenched to room temperature. The resulting microstructure was characterized using electron microscopy and electron back scattered diffraction (EBSD) imaging. It was found that all the untempered regions in the martensitic microstructure were oriented with the plane normals {100} close to the thickness, or normal, direction of the plates. Variant analysis revealed that the untempered regions and the auto-tempered regions are part of the same packet.

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