Report presents discussion of three common and primary influences on embrittlement process. Application of theoretical considerations to design of test coupons and methods is illustrated for both internal and external hydrogen embrittlement. Acceptable designs and methods are indicated

Nelson, H. G.

English

NASA Technical Reports Server

November 1974
	 .	 .	 B74-10222 
NASA TECH BRIEF 
Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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Evaluation of Test Procedures for Hydrogen
Environment Embrittlement 
S
The capacity of an engineering structure to with-
stand an applied load is often degraded severely by 
the presence of hydrogen because it influences frac-
ture behavior. The most extensively studied form of 
hydrogen embrittlement is that which results when 
hydrogen is introduced into the metal lattice by fab-
rication processes such as pickling or electroplating. 
Recently, however, technological advances in the use 
of gaseous hydrogen for propulsion systems or fuel-
cell generation of electricity have required that de-
tailed studies be made of the factors which produce 
embrittlement when clean metal surfaces are directly 
exposed to gaseous hydrogen. 
A review has been made of available literature on 
hydrogen embrittlement in order to define the param-
eters which must be considered in the selection of a 
standardized test method that provides test data 
meaningfully related to real engineering structures. A 
detailed report presents a discussion of the three 
common and primary influences on the embrittlement 
process, i.e., the original location and form of the 
hydrogen, the reactions involved in the transport of 
hydrogen from its origin to some point in the metal 
lattice, and the embrittlement interaction itself; the 
influences of secondary processes are also discussed, 
such as impurity species in the environment, surface 
hydride films, and surface oxide films. A variety of 
test procedures are discussed. 
The application of theoretical considerations to the 
design of test coupons and methods is illustrated for
both internal (processing) and external (environment) 
hydrogen embrittlement. For example, design param-
eters for internal embrittlement must include presence, 
location, and severity of a stress concentrator as well 
as level and form of loading; test coupons must ex-
actly duplicate processing conditions or be carried 
along in actual processing. For external embrittlement 
testing, the influence of each species in the environ-
ment must be understood, or the environment must 
be exactly duplicated; coupons must either contain a 
preexisting crack or must involve the crack-initiation 
stage in the fracture process. Acceptable designs and 
methods are indicated. 
Reference: 
Nelson, H. G.: Testing for Hydrogen Environment 
Embrittlement: Primary and Secondary Influences. 
American Society for Testing and Materials, Special 
Technical Publication 543, p. 152, 1974. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference . B74-10222 
Source: Howard G. Nelson

Ames Research Center

(ARC-10919) 
Category 04 
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Evaluation of test procedures for hydrogen environment embrittlement

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