Effect of Strain Rate on Hydrogen Embrittlement in Ni3Al

The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose, samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then, fracture tests of the pre-charged specimens were performed, using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength, the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.

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Stress Corrosion Cracking of Additively Manufactured Alloy 625

Materials ◽

10.3390/ma14206115 ◽

2021 ◽

Vol 14 (20) ◽

pp. 6115

Author(s):

Marina Cabrini ◽

Sergio Lorenzi ◽

Cristian Testa ◽

Francesco Carugo ◽

Tommaso Pastore ◽

...

Keyword(s):

Heat Treatment ◽

Hydrogen Embrittlement ◽

Strain Rate ◽

Stress Corrosion ◽

Stress Corrosion Cracking ◽

High Strain ◽

Corrosion Cracking ◽

Slow Strain Rate ◽

Laser Source ◽

Alloy 625

Laser bed powder fusion (LPBF) is an additive manufacturing technology for the fabrication of semi-finished components directly from computer-aided design modelling, through melting and consolidation, layer upon layer, of a metallic powder, with a laser source. This manufacturing technique is particularly indicated for poor machinable alloys, such as Alloy 625. However, the unique microstructure generated could modify the resistance of the alloy to environment assisted cracking. The aim of this work was to analyze the stress corrosion cracking (SCC) and hydrogen embrittlement resistance behavior of Alloy 625 obtained by LPBF, both in as-built condition and after a standard heat treatment (grade 1). U-bend testing performed in boiling magnesium chloride at 155 and 170 °C confirmed the immunity of the alloy to SCC. However, slow strain rate tests in simulated ocean water on cathodically polarized specimens highlighted the possibility of the occurrence of hydrogen embrittlement in a specific range of strain rate and cathodic polarization. The very fine grain size and dislocation density of the thermally untreated specimens appeared to increase the hydrogen diffusion and embrittlement effect on pre-charged specimens that were deformed at the high strain rate. Conversely, heat treatment appeared to mitigate hydrogen embrittlement at high strain rates, however at the slow strain rate all the specimens showed a similar behavior.

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On the suitability of slow strain rate tensile testing for assessing hydrogen embrittlement susceptibility

Corrosion Science ◽

10.1016/j.corsci.2019.108291 ◽

2020 ◽

Vol 163 ◽

pp. 108291 ◽

Cited By ~ 13

Author(s):

Emilio Martínez-Pañeda ◽

Zachary D. Harris ◽

Sandra Fuentes-Alonso ◽

John R. Scully ◽

James T. Burns

Keyword(s):

Hydrogen Embrittlement ◽

Strain Rate ◽

Tensile Testing ◽

Slow Strain Rate

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Hydrogen Embrittlement Evaluation of Micro Alloyed Steels by Means of J-Integral Curve

Materials ◽

10.3390/ma12111843 ◽

2019 ◽

Vol 12 (11) ◽

pp. 1843 ◽

Cited By ~ 4

Author(s):

Marina Cabrini ◽

Ennio Sinigaglia ◽

Carlo Spinelli ◽

Marco Tarenzi ◽

Cristian Testa ◽

...

Keyword(s):

Hydrogen Embrittlement ◽

Strain Rate ◽

Crack Propagation Rate ◽

Propagation Rate ◽

Slow Strain Rate ◽

Slow Strain Rate Test ◽

Integral Parameter ◽

Hydrogen Effect ◽

J Integral ◽

Pipeline Steels

The aim of this work is the evaluation of the hydrogen effect on the J-integral parameter. It is well-known that the micro alloyed steels are affected by Hydrogen Embrittlement phenomena only when they are subjected at the same time to plastic deformation and hydrogen evolution at their surface. Previous works have pointed out the absence of Hydrogen Embrittlement effects on pipeline steels cathodically protected under static load conditions. On the contrary, in slow strain rate tests it is possible to observe the effect of the imposed potential and the strain rate on the hydrogen embrittlement steel behavior only after the necking of the specimens. J vs. Δa curves were measured on different pipeline steels in air and in aerated NaCl 3.5 g/L solution at free corrosion potential or under cathodic polarization at −1.05 and −2 V vs. SCE. The area under the J vs. Δa curves and the maximum crack propagation rate were taken into account. These parameters were compared with the ratio between the reduction of area in environment and in air obtained by slow strain rate test in the same environmental conditions and used to rank the different steels.

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Evaluation of Hydrogen Embrittlement of Cr-Mo Low Alloy Steel by Slow Strain Rate Technique With Cathodically Charged Specimen

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2017-65726 ◽

2017 ◽

Author(s):

Daichi Tsurumi ◽

Hiroyuki Saito ◽

Hirokazu Tsuji

Keyword(s):

High Pressure ◽

Hydrogen Embrittlement ◽

Fracture Surface ◽

Strain Rate ◽

Current Density ◽

Cleavage Fracture ◽

Hydrogen Gas ◽

Low Alloy Steel ◽

Slow Strain Rate Technique ◽

Pressure Hydrogen

As an alternative method to slow strain rate technique (SSRT) under high-pressure hydrogen gas evaluation, SSRT was performed with a cathodically charged specimen. Cr-Mo low alloy steel with a tensile strength of 1000 MPa grade was selected as a test material. Cathodic charging was performed in 3% NaCl solution and at a current density in the range of 50–600 A/m2. The effect of specimen size on the hydrogen embrittlement properties was evaluated. Relative reduction of area (RRA) values obtained by tests at a cathode current density of 400 A/m2 were equivalent to those performed in hydrogen gas at pressures of 10 to 35 MPa. Fracture surface observations were also performed using scanning electron microscopy (SEM). The quasi-cleavage fracture surface was observed only after rupture of small specimens that were subjected to hydrogen charged tests. It was also necessary for the diameter of the specimen to be small to form the quasi-cleavage fracture surface. The results indicated that to simulate the high-pressure hydrogen gas test, a specimen with a smaller parallel section diameter that is continuously charged until rupture is preferable.

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Mechanical Properties and Hydrogen Embrittlement of Laser-Surface Melted AISI 430 Ferritic Stainless Steel

Coatings ◽

10.3390/coatings10020140 ◽

2020 ◽

Vol 10 (2) ◽

pp. 140 ◽

Cited By ~ 1

Author(s):

W. K. Chan ◽

C. T. Kwok ◽

K. H. Lo

Keyword(s):

Stainless Steel ◽

Hydrogen Embrittlement ◽

Strain Rate ◽

Ferritic Stainless Steel ◽

Laser Scanning ◽

Electron Backscatter Diffraction ◽

Microstructural Analysis ◽

Scanning Speed ◽

Laser Surface ◽

Aisi 430

In the present study, the feasibility of laser surface melting (LSM) of AISI 430 ferritic stainless steel to minimize hydrogen embrittlement (HE) was investigated. LSM of AISI 430 steel was successfully achieved by a 2.3-kW high power diode laser (HPDL) with scanning speeds of 60 mm/s and 80 mm/s (the samples are designated as V60 and V80, respectively) at a power of 2 kW. To investigate the HE effect on the AISI 430 steel without and with LSM, hydrogen was introduced into specimens by cathodic charging in 0.1 M NaOH solution under galvanostatic conditions at a current density of 30 mA/cm2 and 25 °C. Detail microstructural analysis was performed and the correlation of microstructure with HE was evaluated. By electron backscatter diffraction (EBSD) analysis, the austenite contents for the laser-surface melted specimens V60 and V80 are found to be 0.6 and 1.9 wt%, respectively. The amount of retained austenite in LSM specimens was reduced with lower laser scanning speed. The surface microhardness of the laser-surface melted AISI 430 steel (~280 HV0.2) is found to be increased by 56% as compared with that of the substrate (~180 HV0.2) because of the presence of martensite. The degree of embrittlement caused by hydrogen for the charged and non-charged AISI 430 steel was obtained using slow-strain-rate tensile (SSRT) test in air at a strain rate of 3 × 10−5 s−1. After hydrogen pre-charging, the ductility of as-received AISI 430 steel was reduced from 0.44 to 0.25 while the laser-surface melted AISI 430 steel showed similar tensile properties as the as-received one. After LSM, the value of HE susceptibility Iδ decreases from 43.2% to 38.9% and 38.2% for V60 and V80, respectively, due to the presence of martensite.

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