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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Hydrogen Embrittlement

Hydrogen embrittlement (HE) is a process resulting in a decrease in the fracture toughness or ductility of a metal due to the presence of atomic hydrogen. In addition to pure hydrogen gas as a direct source for the absorption of atomic hydrogen, the damaging effect can manifest itself from other hydrogen-containing gas species such as hydrogen sulfide (H2S), hydrogen chloride (HCl), and hydrogen bromide (HBr) environments. It has been known that H2S environment may result in a much more severe condition of embrittlement than pure hydrogen gas (H2) for certain types of alloys at similar conditions of stress and gas pressure. The reduction of fracture loads can occur at levels well below the yield strength of the material. Hydrogen embrittlement is usually manifest in terms of singular sharp cracks, in contrast to the extensive branching observed for stress corrosion cracking. The initial crack openings and the local deformation associated with crack propagation may be so small that they are difficult to detect except in special nondestructive examinations. Cracks due to HE can grow rapidly with little macroscopic evidence of mechanical deformation in materials that are normally quite ductile. This Technical Memorandum presents a comprehensive review of experimental data for the effects of gaseous Hydrogen Environment Embrittlement (HEE) for several types of metallic materials. Common material screening methods are used to rate the hydrogen degradation of mechanical properties that occur while the material is under an applied stress and exposed to gaseous hydrogen as compared to air or helium, under slow strain rates (SSR) testing. Due to the simplicity and accelerated nature of these tests, the results expressed in terms of HEE index are not intended to necessarily represent true hydrogen service environment for long-term exposure, but rather to provide a practical approach for material screening, which is a useful concept to qualitatively evaluate the severity of hydrogen embrittlement. The effects of hydrogen gas on mechanical properties such as tensile strength, ductility, fracture, low and high cycle fatigue, crack growth rate, and creep rupture are analyzed with respect to the general trends established from the HEE index values. It is observed that the severity of HE effects is also influenced by environmental factors such as pressure, temperature, and hydrogen gas purity. The severity of HE effects is also influenced by material factors such as surface finish, heat treatment, and product forms, compositions, grain direction, and crystal orientations.

Jonathan A. Lee↗
NASA NTRS1989

Hydrogen embrittlement in nickel-hydrogen cells

It was long known that many strong metals can become weakened and brittle as the result of the accumulation of hydrogen within the metal. When the metal is stretched, it does not show normal ductile properties, but fractures prematurely. This problem can occur as the result of a hydrogen evolution reaction such as corrosion or electroplating, or due to hydrogen in the environment at the metal surface. High strength alloys such as steels are especially susceptible to hydrogen embrittlement. Nickel-hydrogen cells commonly use Inconel 718 alloy for the pressure container, and this also is susceptible to hydrogen embrittlement. Metals differ in their susceptibility to embrittlement. Hydrogen embrittlement in nickel-hydrogen cells is analyzed and the reasons why it may or may not occur are discussed. Although Inconel 718 can display hydrogen embrittlement, experience has not identified any problem with nickel-hydrogen cells. No hydrogen embrittlement problem is expected with the 718 alloy pressure container used in nickel-hydrogen cells.

Gross, Sidney↗
NASA NTRS1972

Hydrogen environment embrittlement

Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effect of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed. Additional research is required to determine whether hydrogen environment embrittlement and internal reversible hydrogen embrittlement are similar or distinct types of embrittlement.

Gray, H. R.↗
NASA NTRS1978

Hydrogen Embrittlement and Its Control in Hydrogen-Fueled Engine Systems

The nature of hydrogen embrittlement by high pressure gaseous hydrogen is described and methods of designing SSME gaseous hydrogen systems, including techniques of hydrogen embrittlement prevention, are discussed. The effects of gaseous hydrogen environments are emphasized. Results of extensive investigations of gaseous hydrogen environments on metals conducted under the SSME program are presented.

Chandler, W. T.↗
NASA NTRS1972

Hydrogen environment embrittlement.

Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effects of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed.

Gray, H. R.↗
NASA NTRS1987

Noble Metals Would Prevent Hydrogen Embrittlement

According to proposal, addition of small amounts of noble metals makes iron- and nickel-based alloys less susceptible to embrittlement by hydrogen. Metallurgists demonstrated adding 0.6 to 1.0 percent by weight of Pd or Pt eliminates stress/corrosion cracking in type 4130 steel. Proposal based on assumption that similar levels (0.5 to 1.0 weight percent) of same elements effective against hydrogen embrittlement.

Paton, N. E.↗
NASA NTRS1973

Role of Hf and Zr in the hydrogen embrittlement of Ta and Cb alloys

Investigation of the hydrogen embrittlement of aged Ta alloy T-111 (Ta-8W-2Hf) and similar Ta and Cb alloys. It is found that aging ternary Ta alloys such as T-111 near 1040 C for 1000 hr or longer increases their sensitivity to low-temperature hydrogen embrittlement. Segregation of Hf to grain boundaries during aging causes embrittlement upon testing at -196 C and is responsible for the observed hydrogen embrittlement. Binary Ta and Cb alloys, Ta-2Hf and Cb-1Zr, are not susceptible to hydrogen embrittlement under the conditions of this study and did not exhibit grain boundary segregation of Hf or Zr. Ternary alloys Ta-8W-.5Hf, Ta-8W-1Hf, and Ta-4W-2Hf are superior to T-111 for containment of alkali metals in that they do not exhibit aging embrittlement. However, these alloys in the aged condition are susceptible to hydrogen embrittlement.

Stephens, J. R.↗
NASA NTRS1973

Role of Hf and Zr in the hydrogen embrittlement of Ta and Cb alloys

The hydrogen embrittlement of aged T-111 and similar Ta and Cb alloys is characterized and the mechanisms believed responsible for the increased sensitivity of T-111 to low temperature hydrogen embrittlement after aging for 1000 hours or longer near 1040 C are described. A total of eight Ta base alloys and two Cb base alloys were investigated. The effects of pre-age annealing temperature, aging time, temperature and environment, and alloy composition on the susceptibility to hydrogen embrittlement were investigated. The primary method of determining the effects of these variables on the ductility of T-111 was by bend testing at 25 and -196 C. Fractured specimens were examined by the scanning electron microscope, electron microprobe, metallography and X-ray diffration.

Stephens, J. R.↗
NASA NTRS1974

Role of HF and Zr in the hydrogen embrittlement of Ta and Cb alloys

An attempt is made to characterize the hydrogen embrittlement of aged T-111 and similar Ta and Cb alloys and to describe the mechanisms believed responsible for the increased sensitivity of T-111 to low temperature hydrogen embrittlement after aging for 1000 hr or longer near 1040 C. A total of eight Ta-base alloys and two Cb-base alloys were investigated. The effects of pre-age annealing temperature, aging time, temperature and environment, and alloy composition on the susceptibility to hydrogen embrittlement were investigated. The primary method of determining the effects of these variables on the ductility of T-111 was by bend testing at 25 and -196 C. Fractured specimens were examined by the scanning electron microscope, electron microprobe, metallography, and X-ray diffraction.

Stephens, J. R.↗
DOE OSTI2026

Hydrogen embrittlement and mechanical response of 304L steel with ZrC additions

While stainless steels are widely used for hydrogen storage infrastructure, they can still be vulnerable to hydrogen embrittlement justifying the need to further improve their hydrogen resiliency. Here, we investigate the potential for transition metal carbide additions to improve the hydrogen compatibility of austenitic stainless steels. ZrC nanoparticles were dispersed in contents of 0.01–10 wt% in 304 L stainless steel powder, mixed via high energy ball milling, and subsequently consolidated using direct current sintering. To assess hydrogen compatibility, the tensile properties of similarly processed 304 L without ZrC nanoparticles were compared to 304 L with the ZrC additions; both materials were evaluated prior to and after hydrogen exposure (non-charged and H-precharged, respectively). Depending upon the ZrC phase fraction, the yield strengths varied from ∼325 to 560 MPa in the non-charged condition and from ∼375 to 550 MPa in the H-precharged condition. Strain at failure varied from ∼5 to 90 % and from ∼5 to 35 % in the non-charged and hydrogen-precharged conditions, respectively. Results from stress-strain profiles demonstrate limited efficacy of ZrC as a method to mitigate hydrogen embrittlement entirely but does demonstrate the potency of ZrC inclusions as strengthening addition to 304 L alloys without a loss of ductility.

08 HYDROGEN↗
NASA NTRS2010

Empirical Method to Estimate Hydrogen Embrittlement of Metals as a Function of Hydrogen Gas Pressure at Constant Temperature

High pressure Hydrogen (H) gas has been known to have a deleterious effect on the mechanical properties of certain metals, particularly, the notched tensile strength, fracture toughness and ductility. The ratio of these properties in Hydrogen as compared to Helium or Air is called the Hydrogen Environment Embrittlement (HEE) Index, which is a useful method to classify the severity of H embrittlement and to aid in the material screening and selection for safety usage H gas environment. A comprehensive world-wide database compilation, in the past 50 years, has shown that the HEE index is mostly collected at two conveniently high H pressure points of 5 ksi and 10 ksi near room temperature. Since H embrittlement is directly related to pressure, the lack of HEE index at other pressure points has posed a technical problem for the designers to select appropriate materials at a specific H pressure for various applications in aerospace, alternate and renewable energy sectors for an emerging hydrogen economy. Based on the Power-Law mathematical relationship, an empirical method to accurately predict the HEE index, as a function of H pressure at constant temperature, is presented with a brief review on Sievert's law for gas-metal absorption.

Lee, Jonathan A.↗
DOE OSTI2026

Assessment of Vibration and Shock Loading Environments on Steels Used in Railroad Applications Considering Hydrogen Embrittlement

Studies that examine the combined effects of hydrogen and rail loading environments in the context of hydrogen embrittlement of steels have not been performed. Large-scale hydrogen storage requires either gaseous hydrogen stored in pressure vessels and tubing or liquid hydrogen in cryogenic, insulated tanks. Since the focus of this study is on steels, we examine the influence of hydrogen on stainless steel used for high pressure tubing and cryogenic tanks and Cr-Mo steel liners used in gaseous pressure vessels. Literature studies show that despite hydrogen degradation, these steels can be used effectively and safely if the stresses are managed. The shock and vibration environment on railcars present unique environments where stresses and loading rates can be high. A literature review was conducted to understand the accelerations experienced in rail by examining instrumented railcars of nuclear fuel casks. Hydrogen studies were examined that focused on steel pressure hardware with an emphasis on fatigue, fast loading rates, and low temperatures. A simplified fatigue assessment was performed to examine design cycles for three different hydrogen components: stainless steel tubing, stainless steel cryogenic tanks, and gaseous pressure vessels. The assessments were idealized and used bounding cases of accelerations in both normal rail conditions and coupling events. In normal shock and vibration environments when accelerations were less than 2 g, infinite design life was calculated. In extreme shock or coupling environments, finite design life was calculated which was shown to be dependent on unsupported lengths of pressure components. It was shown that adjusting the unsupported length can reduce the bending stress thereby increasing design life.

36 MATERIALS SCIENCE↗