Effect of Thickness on the Charpy Energy of - Charged 4340 Steel

O. S. Es-Said, J. Alcisto, J. Guerra, E. Jones, A. Dominguez, M. Hahn, N. Ula, L. Zeng, B. Ramsey, H. Mulazimoglu, Yong-Jun Li, et al.

Journal of Materials Engineering and Performance

ISSN 1059-9495 Volume 25 Number 9

J. of Materi Eng and Perform (2016) 25:3606-3614 DOI 10.1007/s11665-016-2246-6

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1 23 Author's personal copy JMEPEG (2016) 25:3606–3614 ÓASM International DOI: 10.1007/s11665-016-2246-6 1059-9495/$19.00 Effect of Cadmium Plating Thickness on the Charpy Impact Energy of Hydrogen-Charged 4340 Steel O.S. Es-Said, J. Alcisto, J. Guerra, E. Jones, A. Dominguez, M. Hahn, N. Ula, L. Zeng, B. Ramsey, H. Mulazimoglu, Yong-Jun Li, M. Miller, J. Alrashid, M. Papakyriakou, S. Kalnaus, E.W. Lee, and W.E. Frazier

(Submitted February 29, 2016; in revised form June 3, 2016; published online July 22, 2016)

Hydrogen was intentionally introduced into ultra-high strength steel by cadmium plating. The purpose was to examine the effect of cadmium plate thickness and hence hydrogen on the impact energy of the steel. The AISI 4340 steel was austenitized at 1000 °C for 1 h, water quenched, and tempered at temperatures between 257 and 593 °C in order to achieve a range of targeted strength levels. The specimens were cadmium plated with 0.00508 mm (0.2 mils), 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils). Results demonstrated that the uncharged specimens exhibited higher impact energy values when compared to the plated specimens at all temperatures. The cadmium-plated specimens had very low Charpy impact values irrespective of their ultimate tensile strength values. The model of hydrogen transport by mobile dislocations to the site appears to provide the most suitable explanation of the results.

stabilization mechanism), the assumption is that hydrogen Keywords 4340 steel, cadmium plating, , hydrogen charging promotes vacancy agglomeration which lowers the ductility in steels that fail through microvoid coalescence. The HE literature is rich; however, the actual mechanisms leading to failure of metals by this phenomenon is still not clear. What is accepted is that hydrogen migrates to stress concentration 1. Introduction locations and facilitates fracture. HE is a long-standing problem in the gas and oil industry, in the storing and transport of hydrogen (Ref 14), automotive Hydrogen charging (absorption) occurs in different pro- parts that require ultra-high strength for crash protection in cesses. These include , heat treatment, rollover and in side-impact accidents (Ref 7, 15-17), modern fuel cell reactions, pickling, steel making, and cathodic motor architecture (Ref 18), aircraft landing gears and protections (Ref 1-7). The detrimental effect of hydrogen on fasteners (Ref 19), and off shore platforms, tankers, and navy the properties of metals has been documented (Ref 3-13). ships (Ref 20). (HE) is known to affect high Several tests exist that can detect the amount of hydrogen strength steel components like springs and screws. Several in steels (Ref 21, 22). These detection methods can be very models were proposed to understand the mechanisms of HE. time-consuming and difficult to carry out. Traditionally, Rehrl et al. (Ref 7) and Neeraje et al. (Ref 14) reviewed the sustained load time-to-failure or stress durability test for models that coincide at the point that hydrogen diffusion into hydrogen embrittlement in steels required many machines, stress concentration fields is necessary to promote HE. These used up to 12-14 samples and could take minimum 96 h up to models were HEDE, HELP, and VM. In HEDE (hydrogen- 4 or 5 years. The incremental step loading technique for enhanced decohesion), the assumption is that hydrogen reduces measurements of hydrogen embrittlement in steel, however, is the atomic bonds strength, decreases the surface energy, and a more efficient method which only utilizes one machine and can accelerate in a stress field the initiation and propagation of is completed within 1 week (Ref 22). This test method cracks. In hydrogen-enhanced localized plasticity (HELP), the measures the subcritical crack growth with a step modified assumption is that the presence of hydrogen gas enhances the incrementally increasing slow strain rate test. The load rate mobility of dislocations. In VM (hydrogen-enhanced vacancy must be slow in order to permit hydrogen to diffuse and induce cracking. O.S. Es-Said, J. Alcisto, J. Guerra, E. Jones, A. Dominguez, Szczopanski (Ref 23) indicated that hydrogen affects the M. Miller, J. Alrashid, and M. Papakyriakou, Mechanical results of an impact test. Jean (Ref 24) predicted that Charpy Engineering Department, Loyola Marymount University, Los Angeles, CA 90045; M. Hahn, F-35 Materials and Processes, Northrop- impact test would detect the presence of hydrogen in metals. Grumman, Redondo Beach, CA 90278; N. Ula, Electrical Engineering His (Ref 24) experimental results did not confirm his Department, Loyola Marymount University, Los Angeles, CA 90045; hypothesis. In a recent study by Mori et al. (Ref 25), same L. Zeng and B. Ramsey, Sargent Aerospace and Defense, Torrance, CA group in this study, showed that Charpy impact testing can 90502; H. Mulazimoglu, ALCOA Fastening Systems and Rings, clearly detect the presence of hydrogen when the tempering Torrance, CA 90502; Yong-Jun Li, MANE Laboratories, College of temperatures exceed 468 °C. Their results were explained by Science and Engineering, Loyola Marymount University, Los Angeles, CA 90045; S. Kalnaus, Oak Ridge National Laboratory, Computational a model which suggests that hydrogen can be transported Engineering and Energy Sciences Group, Oak Ridge, TN 3783; and rapidly by mobile dislocations to the fracture site. For E.W. Lee and W.E. Frazier, Naval Air Systems Command, Patuxent transport mode, hydrogen may diffuse by the normal River, MD 20670. Contact e-mail: [email protected].

3606—Volume 25(9) September 2016 Journal of Materials Engineering and Performance Author's personal copy interstitial diffusion mode or can be carried by mobile dislocations is faster and the interaction between hydrogen dislocations or along short-circuit paths. The difference and dislocations is more energetic (Ref 26). Bastein and Azou between these various modes by which hydrogen diffuses is (Ref 27) in 1951 first suggested that dislocations could fundamental. Interstitial diffusion is slow, while transport by transport hydrogen atmosphere at rates faster than lattice

Fig. 1 (a) Tensile bar dimensions (Ref 17). (b) The dimensions (mm) of Charpy impact V-notched specimen which is based on ASTM E23-12c

Fig. 2 (a) Removing scale from Charpy impact specimens. (b) Removing scale from tensile specimens. Lower picture shows the effect after etching 8 h in 25% HCl solution

Table 1 Desired UTS and the obtained UTS after tempering at the specified temperatures for uncharged specimens

Uncharged desired Uncharged desired Uncharged obtained Uncharged obtained Temperature, °C UTS, ksi UTS, MPa UTS, ksi UTS, MPa Percent difference

593 145 1000 142 976 2 545 160 1103 153 1052 5 513 170 1172 163 1120 4 481 180 1241 184 1266 À2 449 190 1310 177 1219 7 401 205 1413 193 1333 6 353 220 1517 211 1458 4 257 250 1724 241 1664 3

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Fig. 5 Energy absorbed vs. strength for the range of tempers inves- tigated Fig. 3 Ultimate strength vs. tempering temperature for uncharged and charged specimens

Fig. 4 Average impact energy vs. tempering temperature for un- charged and charged specimens

diffusion rates and that this hydrogen could be trapped in voids, leading to internal pressure enhancement and to failure. The concept that ‘‘dislocations transport’’ and ‘‘trapping’’ are competing processes was initiated by Tien et al. (Ref 26)and Fig. 6 As received after being austenitized, oil quenched, and tem- expanded upon by Pressouyre and Bernstein (Ref 28)to pered at 232 °C include competition between weak and strong traps (grain boundaries, inclusions, voids, dislocation arrays, and solute atoms). 0.8%), Mo (0.2-0.3%), Ni (1.65-2.0%), and Si (0.15-0.3%) (Ref The objective of this research is to follow-up on the 29). A Sodick AQ325L Electro Discharge Machine (EDM) was previous study (Ref 25) and to determine the effect of used to cut the as-received plate into 96 Charpy specimens and different cadmium plating thicknesses (varying hydrogen 96 tensile specimens. charging content) on the Charpy impact values of 4340 steel. The dimensions of the tensile specimens were in accordance Specifically, this work addresses the question whether a with ASTM E8 (Ref 30), and tensile testing was performed on simple, high strain rate, fast procedure, namely Charpy impact an INSTRON 4505 universal testing unit. The standard Charpy testing, can detect the presence of hydrogen in ultra-high V-notch specimens were machined according to ASTM E23 strength steels or not? (Ref 31) and were tested by a SONNTAG Impact Tester with a 325-J capacity, S/N model 044-1811. Dimensions of the specimens are shown in Fig. 1(a, b). 2. Experimental Procedure 2.2 Heat Treatments 2.1 Specimen Preparation The 192 (Charpy and tensile) specimens were austenitized at A plate of 4340 steel (61 9 15 9 15 cm in dimensions) was 1000 °C for 1 h and water quenched to form martensite, and obtained from the American Foundry Society (AFS). The initial then, they were separated into eight groups which were condition of the plate was austenization, followed by oil tempered at a range of temperatures (257, 353, 401, 449, quenching and tempering at 232 °C for 2 h. The alloying 481, 513, 545, and 593 °C) to achieve target tensile strengths elements are carbon (0.37-0.43%), Cr (0.7-0.9%), Mn (0.6- of: 1000, 1103, 1172, 1241, 1310, 1413, 1517, and 1724 MPa

3608—Volume 25(9) September 2016 Journal of Materials Engineering and Performance Author's personal copy (145, 160, 170, 180, 190, 205, 220, and 250 ksi), respectively. assumption that the thicker the coating, the more the presence The tempering duration was 2 h followed by air cooling. of hydrogen in the specimens due to longer time plating. One The water quenched and tempered specimens had a thick group was left uncharged with no cadmium plating. It should be scale of black oxide. A tedious effort was spent in removing the noted that the authors are working on a project where they will oxide layer. These efforts included chemical immersion in 25% have the amount of hydrogen measured and correlated with HCl solution, Fig. 2(a, b), and using a grooving tool to machine cadmium coating thicknesses. They are also working on the notches of the Charpy impact specimens, and linear correlating fracture data with Charpy impact data profiling on the tensile samples. and to the amount of hydrogen absorbed. The 96 Charpy and the 96 tensile specimens were divided into four groups. Each group was composed of 24 specimens of 2.3 Scanning Electron Microscopy each. Three Charpy impact specimens and three tensile specimens were tested at each of the eight tempering temper- Scanning electron microscopy (SEM) was conducted using atures. Three of the four groups were sent to Alcoa Fasteners, FEI Quanta 200 JSM-6400 SEM on the fractured surfaces of Inc., to be cadmium plated at 0.00508 mm (0.2 mils), twelve of the Charpy specimens. Three specimens were chosen 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils). This was from each coating thickness [uncharged, 0.00508 mm completed in accordance with AMS 2400 and AMs-QQ-P-416 (0.2 mils), 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils)], specifications (Ref 32). The purpose was to intentionally induce and the magnifications were at 1009, 5009, 10009, and different levels of hydrogen charging in the specimens with the 50009.

Fig. 7 (a) Specimens tempered at 593 °C to produce a target strength of 1000 MPa (145 ksi) (uncharged), 9100 magnification. (b) Specimens tem- pered at 593 °C to produce a target strength of 1000 MPa (145 ksi) [0.00508 mm (0.2 mils)], 9100 magnification. (c) Specimens tempered at 593 °C to produce target strength of 1000 MPa (145 ksi) [0.00762 mm (0.3 mils)], 9100 magnification. (d) Specimens tempered at 593 °C to pro- duce a target strength of 1000 MPa (145 ksi) [0.0127 mm (0.5 mils)], 9100 magnification. (e) Specimens tempered at 593 °C to produce a target strength of 1000 MPa (145 ksi) (uncharged), 9500 magnification. (f) Specimens tempered at 593 °C to produce a target strength of 1000 MPa (145 ksi) [0.00508 mm (0.2 mils)], 9500 magnification. (g) Specimens tempered at 593 °C to produce target strength of 1000 MPa (145 ksi) [0.00762 mm (0.3 mils)], 9500 magnification. (h) Specimens tempered at 593 °C to produce a target strength of 1000 MPa (145 ksi) [0.0127 mm (0.5 mils)], 9500 magnification

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Fig. 7 continued

3. Results and Discussion Room-temperature tension testing was performed on the specimens, which had been tempered in the temperature range The results of the previous work (Ref 25) performed by this (257-593 °C). The tempering temperatures aimed to produce a group indicated that Charpy impact tests were successful in range of tensile strength values from 1000 MPa (145 ksi) to showing a quantitative clear difference between hydrogen- 1724 MPa (250 ksi). The obtained tensile strengths and the charged and uncharged specimens at tempering temperatures desired values differed by (À2 to 7%), as shown in Table 1. The ultimate strength values were almost identical between exceeding 468 °C. Below this temperature, the Charpy impact energy values did not show any difference between the all the four groups Fig. 3. The range was between 900 and behavior of the hydrogen-charged and uncharged specimens. 1700 MPa. The average impact energy values versus tempering This was due to the brittleness of this region because of the temperature in Fig. 4 showed a clear difference between the low-temperature tempering where the percent elongation values uncharged and charged specimens at all temperatures. A subtle were less than 10%. difference exists between the values of the charged specimens, In the previous work (Ref 25), the tempering was performed the 0.00508 mm (0.2 mils) specimens performed slightly better than the 0.00762 mm (0.3 mils) and 0.0127 mm (0.5 mils) between 354 and 621 °C. In this work, two changes were implemented: plated specimens. The data of the latter two (0.00762 mm (0.3 mils) and 0.0127 mm (0.5 mils) plated specimens) were 1. The specimens were re-austenitized and water quenched very close. Possibly performing the test with a larger number of to form martensite prior to tempering. The oxide layer specimens might clarify these differences. These results clearly was removed prior to mechanical testing. indicate that Charpy impact testing can detect quantitatively the 2. Three levels of cadmium plating were evaluated presence of hydrogen in ultra-high strength steels. These results [0.00508 mm (0.2 mils), 0.00762 mm (0.3 mils), and are not in accord with the interpretation of Ref (15). This study 0.0127 mm (0.5 mils)]. (Ref 15) interprets that hydrogen assimilation and hydrogen

3610—Volume 25(9) September 2016 Journal of Materials Engineering and Performance Author's personal copy diffusion are more favorable at slower stress or strain rates and specimens displayed a mixed mode, Fig. 7(a-d). The uncharged that impact testing is not useful in studying HE. and the 0.00508 mm (0.2 mils) plated specimens showed more The Charpy energy versus the ultimate tensile strength ductile patterns with some equiaxed dimples (Fig. 7a and b). values in Fig. 5 show an interesting pattern. The Charpy impact This is in accord with the observations of low strength levels energy for uncharged specimens decreases with the increase in (Fig. 3) and high Charpy impact energy values, Fig. 4. The strength and reaches a plateau at 40 N-m from 1000 MPa to 0.00762 mm (0.3 mils) and 0.0127 mm (0.5 mils) specimens higher strength values. On the other hand, all the plated showed more brittle regions, which are in accord with the specimens show low Charpy impact values at all strength lowest Charpy impact energy values, Fig. 4. For clarity, levels. The 0.00508 mm (0.2 mils) plated specimens had Fig. 7(e, f, g, h) is the same as Fig. 7(a-d) but at a magnification slightly better energy values at lower strength compared to the of 5009 instead of 1009. For specimens tempered at 449 °Cto 0.00762 mm (0.3 mils) and 0.0127 mm (0.5 mils) cadmium- produce a target strength of 1310 MPa (190 ksi), all the plated specimens. This indicates that impact testing is specimens displayed a mixed mode. However, all specimens a very efficient way of detecting the existence of hydrogen showed more ductile patterns with some equiaxed dimples quickly. (Fig. 8a-d). The uncharged specimens had higher Charpy The fracture surfaces of the Charpy impact specimens were impact values which explain the ductile patterns. The charged investigated. The SEM micrographs were chosen at 1009 samples showed equivalent or finer dimples. Pre-charged magnifications to capture a larger area. The as-received hydrogen at large second-phase particles reduces the resistance specimens, Fig. 6, had a mixed mode pattern more inclined to microvoid formation at their interfaces. Accordingly, a ‘‘void toward brittleness. For specimens tempered at 593 °Cto sheet’’ formation may occur due to strain localization between produce a target strength of 1000 MPa (145 ksi), all the voids and smaller microvoids can occur as compared to the

Fig. 8 (a) Specimens tempered at 449 °C to produce a target strength of 1310 MPa (190 ksi) (uncharged). (b) Specimens tempered at 449 °C to produce a target strength of 1310 MPa (190 ksi) [0.00508 mm (0.2 mils)]. (c) Specimens tempered at 449 °C to produce a target strength of 1310 MPa (190 ksi) [0.00762 mm (0.3 mils)]. (d) Specimens tempered at 449 °C to produce a target strength of 1310 MPa (190 ksi) [0.0127 mm (0.5 mils)]

Journal of Materials Engineering and Performance Volume 25(9) September 2016—3611 Author's personal copy microvoids formed in hydrogen-free specimens (Ref 33). interfaces, thus resulting in the lowering of cohesive strength. Similar observations of the ‘‘void sheet formulation’’ were Under the appropriate conditions where leakage out of voids is reported in (Ref 1, 5-9, 14, 16, 34) This effect is even more slow, hydrogen-carrying dislocations can pressurize voids and, evident for specimens tempered at 257 °C to produce a target hence, aid in faster dimple growth (Ref 36). Except at strength of 1724 MPa (250 ksi). The uncharged specimens extremely short times, dislocations can carry hydrogen much display a mixed mode with more of a brittle nature, Fig. 9(a), deeper into the material than lattice diffusion can. Mobile while the charged specimens which are 0.00508 mm (0.2 mils), dislocations are able to transport hydrogen to material weak 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils) plated links much more rapidly than lattice diffusion can (Ref 37). (Fig. 9b-d) display a mixed mode but with ductile microvoid Lattices might be enriched with hydrogen atoms by the regions which are small in size. It is noted that from Fig. 4, the dislocation sweeping mechanism through two major means: Charpy impact values of the uncharged specimens are over one (dislocation annihilation model) is by the annihilation of 40 N-m, and for the charged 0.00508 mm (0.2 mils), hydrogen-carrying mobile dislocations with each other, and the 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils) cadmium- other (stripping model) is by the transfer of hydrogen from the plated specimens, the values are less than 20 N-m. Toughness dislocations to deeper traps such as grain boundaries, inclu- is lowered by mechanisms that favor void sheets. sions, or precipitate interfaces and voids as the mobile The results of this work are best explained by the dislocations encounter these obstacles (Ref 36). ‘‘Dislocation Transport (Sweeping) of Hydrogen.’’ This model When the interfaces between second-phase particles and the was endorsed by a group of researchers on dislocation transport matrix form voids, or in the case of preexisting voids, the result of hydrogen (Ref 35-37). The dislocation-hydrogen interaction is the pressurization of voids with hydrogen. This pressuriza- and sweeping velocity model indicates that dislocations can tion may further contribute to speedy embrittlement though deliver hydrogen to traps such as grain boundaries and other enhancement of crack growth or dimple growth in ductile

Fig. 9 (a) Specimens tempered at 257 °C to produce a target strength of 1724 MPa (250 ksi) (uncharged). (b) Specimens tempered at 257 °C to produce a target strength of 1724 MPa (250 ksi) [0.00508 mm (0.2 mils)]. (c) Specimens tempered at 257 °C to produce a target strength of 1724 MPa (250 ksi) [0.00762 mm (0.3 mils)]. (d) Specimens tempered at 257 °C to produce a target strength of 1724 MPa (250 ksi) [0.0127 mm (0.5 mils)]

3612—Volume 25(9) September 2016 Journal of Materials Engineering and Performance Author's personal copy materials (Ref 36-38). Leakage from the void or inclusion • The results were again explained, like in the previous interface can prevent significant pressurization if dissociation work, by the model of hydrogen transport by mobile dis- catalysts segregate to the interface. locations to the fracture site. This model was also extended to nonferrous alloys. • During this investigation, hydrogen embrittlement mecha- Concurrent plastic straining during cathodic charging of nism seems consistent with the increased dislocation equiaxed-grain, high-purity 7075 aluminum, seems to indicate mobility in the presence of hydrogen, leading to an in- that dislocations can transport large amounts of hydrogen deep crease in local plasticity and void formations. into the interior of the alloy. A complicating factor in such an • SEM results again indicated that charged surfaces were argument and, in fact, in completely understanding the direct populated by fine numerous microvoids, as compared to role of hydrogen is that lattice transport of hydrogen is hydrogen-free surfaces. extremely slow in aluminum, making it difficult to rationalize how hydrogen can keep up with a moving crack, or be transported to a crack region solely by volume diffusion. One solution to this question would be the existence of a more rapid References transport mode for hydrogen, as solute atmospheres associated with mobile dislocations (Ref 38-41). 1. G.L. Nash, H. Choo, P. Nash, L.L. Daemen, and M.A.M. Bourke, In a recent study by Rehrl et al. (Ref 7), four ultra-high Lattice Dilation in a Hydrogen Charged Steel, International Centre for strength steels with tensile strength values between 1200 and Diffraction Data, Adv. X-Ray Anal., 2003, 46, p 238–239 1400 MPa were tensile tested at significantly different loading 2. J.M. Tartaglia, K.A. Lazzari, G.P. Hui, and K.L. Hayrynen, A À5 Comparison of Mechanical Properties and Hydrogen Embrittlement rates (10 /s and 20/s). All hydrogen-charged grades tested at Resistance of Austempered vs Quenched and Tempered 4340 Steel, J. the high strain rate exhibited fully ductile fracture with a Metall. Mater. Trans. A., 2008, 39A, p 559–576 significant amount of dimples. They (Ref 7) concluded that 3. H. Uyama, M. Nakashima, K. Morishige, Y. Mine, and Y. Murakami, hydrogen-induced fracture is a combination of both enhanced Effects of Hydrogen Charge on Microscopic Behavior of Annealed Carbon Steels, J. Fatigue Fract. Eng. Mater. Struct., 2006, dislocation mobility by hydrogen (HELP) and decohesion 29, p 1066–1074 prompted by hydrogen transport through dislocations. They 4. I.O. Shim and J.G. Bryne, Microstructural Structural Response of 4340 indicated that the movement of hydrogen with dislocations is Steel to Hydrogen Charging, J. Eng. Mater., 1990, 12, p 235–244 possible for low and for high strain tests. 5. I.A. Barnoush, Hydrogen Embrittlement. http://www.uni-saarland.de/ Robertson (Ref 42) studied the effects of hydrogen on fak8/wwm/research/phd_barnoush/hydrogen.pdf. N.p., 1 Dec 2011. dislocation dynamics. His environmental cell TEM studies Web. 2 Feb 2014, p 13–19 6. N.C. Uwakweh, C. Oswald, A. Samuel, and S. Vinod, Hydrogen provided direct evidence that hydrogen can increase the Charging of AISI-321 Austenitic by Cathodic Polar- velocity of edge, screw, partial, and perfect dislocations in ization, in Tri-Service Corrosion Conference, 2005, p 1–16 FCC (Ni), BCC (iron), and HCP (Ti) structures. Lynch (Ref 43) 7. J. Rehrl, K. Mraczek, A. Pichler, and E. Werner, Mechanical Properties proposed that crack advance in a vacuum occurred by and Fracture Behavior of Hydrogen Charges AHSS/UHSS Grades at dislocations from the bulk moving to and being absorbed at High- and Low Strain Rate Tests, Mater. Sci. Eng. A, 2014, 590, p 360– the crack tip. Birnbaum and Sofronis (Ref 44) proposed that 367 8. J.P. Hirth, Effects of Hydrogen on the Properties of Iron and Steel, hydrogen formed an atmosphere around dislocations. The Metall. Trans. A, 1980, 11, p 861–890 redistribution of the hydrogen atmosphere shields the disloca- 9. H. Luo, C.F. Dong, Z.Y. Liu, M.T.J. Maha, and X.G. Li, Character- tions from interaction and allows them to move at lower levels ization of Hydrogen Charging of 2205 Duplex Stainless Steel and its of applied stress. May et al. (Ref 45) suggested that voids Correlation with Hydrogen-Induced Cracking, Mater. Corros., 2013, initiate and propagate along the intersection between slip bands. 64, p 26–29 10. A. Valiente, J. Toribio, R. Cortes, and L. Caballero, Tensile Failure of These voids widen by the help of dislocations and produce the Stainless-Steel Notched Bars Under Hydrogen Charging, J. Eng. features of the observed fracture surfaces. Hydrogen assists in Mater. Technol., 1996, 118, p 118–191 the development of the slip bands, lowers the stress needed to 11. R. Fratesi and G. Roventi, Hydrogen-Inclusion Interaction in Tempered initiate, and accelerates the expansion of voids. Martensite Embrittled SAE 4340 Steels, Mater. Sci. Eng. Struct. Mater. Irrelevant of which mechanism is more accurate, the results Prop. Microstruct. Process., 1989, 119, p 17–22 of this study indicating hydrogen effects on lowering the 12. R.W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th ed., J. Wiley & Sons, New York, 1996, p 485–514 Charpy impact energy values of cadmium-coated samples is a 13. R.P. Gangloff, Hydrogen Assisted Cracking of High Strength Alloys, in further evidence that the mobility of hydrogen cannot be Comprehensive Structural Integrity, vol. 6. Elsevier Science, New explained only by the low values of interstitial diffusion York, 2003, p 1–7 coefficients. 14. T. Neeraj, R. Srinivasan, and J. Li, Hydrogen Embrittlement of Ferritic Steels: Observations on Deformation Microstructure, Nanoscale Dim- ples and Failure by Nanovoiding, Acta Mater., 2012, 60, p 5160–5171 15. J. Venenzuela, Q. Liu, M. Zhang, Q. Zhou, and A. Atrens, The 4. Conclusions Influence of Hydrogen on the Mechanical and Fracture Properties of Some Martensitic Advanced High Strength Steels Studied Using the Linearly Increasing Stress Test, Corros. Sci., 2015, 99, p 98–117 • Results of Charpy impact tests indicate that this technique 16. S.-J. Lee, J. Aronevich, G. Krauss, and D. 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3614—Volume 25(9) September 2016 Journal of Materials Engineering and Performance