ASTM_F_2078_-_15.pdf

Designation:F207815Standard Terminology Relating toHydrogen Embrittlement Testing1This standard is issued under the fixed designation F2078;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 Thisterminologycoverstheprincipalterms,abbreviations,and symbols relating to mechanical methods forhydrogen embrittlement testing,which are present in more thanone of the standards under the jurisdiction of ASTM Commit-tee F07 on Aerospace and Aircraft.These definitions arepublished to encourage uniformity of terminology in productspecifications.2.Referenced Documents2.1 ASTM Standards:2C904 Terminology Relating to Chemical-Resistant Nonme-tallic MaterialsD4848 Terminology Related to Force,Deformation andRelated Properties of TextilesE6 Terminology Relating to Methods of Mechanical TestingE8 Test Methods for Tension Testing of Metallic MaterialsE631 Terminology of Building ConstructionsE1823 Terminology Relating to Fatigue and Fracture TestingF109 Terminology Relating to Surface Imperfections onCeramicsF1624 Test Method for Measurement of Hydrogen Em-brittlement Threshold in Steel by the Incremental StepLoading TechniqueG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)33.Significance and Use3.1 The terms used in describing hydrogen embrittlementhave precise definitions.The terminology and its proper usagemust be completely understood to communicate and transferinformation adequately within the field.3.2 The terms defined in other terminology standards,arerespectively identified in parentheses following the definition.4.Terminology4.1 Definitions:bakingheating to a temperature,not to exceed 50F(27.8C)below the tempering or aging temperature of the metal oralloy,in order to remove hydrogen before embrittlementoccurs by the formation of microcracks.DISCUSSIONNo metallurgical changes take place as a result ofbaking.brittlesee brittleness.brittlenessthe tendency of a material to break at a very lowstrain,elongation,or deflection,and to exhibit a cleanfracture surface with no indications of plastic deformation.(E631)crackline of fracture without complete separation.(F109)crack strengththe maximum value of the nominal stress thata cracked specimen is capable of sustaining.(E1823)ductilesee ductility.ductilitythe ability of a material to deform plastically beforefracturing.(E6)embrittlesee embrittlement.embrittlementthe severe loss of ductility or toughness,orboth,of a material,usually a metal or alloy.(G15)environmental hydrogen embrittlement(EHE)hydrogenembrittlement caused by hydrogen introduced into a steel/metallic alloy from an environmental source coupled withstress either residual or externally applied.DISCUSSIONProduces a clean intergranular fracture and is notreversible.For the subtle differences between EHE and IHE,see TableX1.1.environmentally assisted cracking(EAC)see stress cor-rosion cracking.fracture strengththe normal stress at the beginning offracture.gaseous hydrogen embrittlement(GHE)a distinct form ofEHE caused by the presence of external sources of highpressure hydrogen gas;cracking initiates on the outersurface.1This terminology standard is under the jurisdiction of ASTM Committee F07on Aerospace and Aircraft and is the direct responsibility of Subcommittee F07.04on Hydrogen Embrittlement.Current edition approved Nov.1,2015.Published November 2015.Originallyapproved in 2001.Last previous edition approved in 2008 as F207808A.DOI:10.1520/F2078-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 heat treatmentheating and cooling processes that producemetallurgical changes in the metallic alloy which alter themechanical properties and microstructure of the metal.hydrogen-assisted stress cracking(HASC)crack growthas a result of the presence of hydrogen,which can be eitherIHE or EHE and sometimes is referred to as hydrogen stresscracking(HSC).hydrogen embrittlement(HE)a permanent loss of ductilityin a metal or alloy caused by absorption of hydrogen incombination with stress,either an externally applied or aninternal residual stress.hydrogen embrittlement reliefsee baking.hydrogen-induced stress crackingsee hydrogen-assistedstress cracking.hydrogen stress crackingsee hydrogen-assisted stresscracking.hydrogen susceptibility ratio(Hsr)the ratio of the thresh-old for the onset of hydrogen-assisted cracking to the tensilestrength of the material.internal hydrogen embrit