1、Designation: F2078 08aF2078 15Standard 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 nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This terminology covers the principal terms, abbreviations, and symbols relating to mechanical methods for hydrogenembrittlement testing,
3、 which are present in more than one of the standards under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft. These definitions are published to encourage uniformity of terminology in product specifications.2. Referenced Documents2.1 ASTM Standards:2C904 Terminology Relating to Chemica
4、l-Resistant Nonmetallic MaterialsD4848 Terminology Related to Force, Deformation and Related 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
5、Fatigue and Fracture TestingF109 Terminology Relating to Surface Imperfections on CeramicsF1624 Test Method for Measurement of Hydrogen EmbrittlementThreshold in Steel by the Incremental Step LoadingTechniqueG15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)33. Significance
6、 and Use3.1 The terms used in describing hydrogen embrittlement have precise definitions. The terminology and its proper usage mustbe completely understood to communicate and transfer information adequately within the field.3.2 The terms defined in other terminology standards, are respectively ident
7、ified 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 or alloy,in order to remove hydrogen before embrittlement occurs by the formation of microcracks.DISCUSSIONNo me
8、tallurgical changes take place as a result of baking.brittlesee brittleness.brittlenessthe tendency of a material to break at a very low strain, elongation, or deflection, and to exhibit a clean fracturesurface with no indications of plastic deformation. (E631)crackline of fracture without complete
9、separation. (F109)crack strengththe maximum value of the nominal stress that a cracked specimen is capable of sustaining. (E1823)1 This terminology standard is under the jurisdiction of ASTM Committee F07 on Aerospace and Aircraft and is the direct responsibility of Subcommittee F07.04 onHydrogen Em
10、brittlement.Current edition approved July 1, 2008Nov. 1, 2015. Published July 2008November 2015. Originally approved in 2001. Last previous edition approved in 2008 asF207808.08A. DOI: 10.1520/F2078-08A.10.1520/F2078-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactA
11、STM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended o
12、nly to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current ver
13、sionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1ductilesee ductility.ductilitythe ability of a material to deform plastically before fracturing. (E6)em
14、brittlesee embrittlement.embrittlementthe severe loss of ductility or toughness, or both, of a material, usually a metal or alloy. (G15)environmental hydrogen embrittlement (EHE) hydrogen embrittlement caused by hydrogen introduced into a steel/metallicalloy from an environmental source coupled with
15、 stress either residual or externally applied.DISCUSSIONProduces a clean intergranular fracture and is not reversible. For the subtle differences between EHE and IHE, see Table X1.1.environmentally assisted cracking (EAC) see stress corrosion cracking.fracture strengththe normal stress at the beginn
16、ing of fracture.gaseous hydrogen embrittlement (GHE)a distinct form of EHE caused by the presence of external sources of high pressurehydrogen gas; cracking initiates on the outer surface.heattreatmentheating and cooling processes that produce metallurgical changes in the metallic alloy which alter
17、the mechanicalproperties and microstructure of the metal.hydrogen-assisted stress cracking (HASC) crack growth as a result of the presence of hydrogen, which can be either IHE orEHE and sometimes is referred to as hydrogen stress cracking (HSC).hydrogenembrittlement(HE)a permanent loss of ductility
18、in a metal or alloy caused by absorption of hydrogen in combinationwith stress, either an externally applied or an internal residual stress.hydrogen embrittlement reliefsee baking.hydrogen-induced stress crackingsee hydrogen-assisted stress cracking.hydrogen stress crackingsee hydrogen-assisted stre
19、ss cracking.hydrogen susceptibility ratio (Hsr)the ratio of the threshold for the onset of hydrogen-assisted cracking to the tensile strengthof the material.internal hydrogen embrittlement (IHE) hydrogen embrittlement caused by absorbed atomic hydrogen into the steel/metallicalloy from an industrial
20、 hydrogen emitting process coupled with stress, either residual or externally applied.DISCUSSIONFor the subtle differences between IHE and EHE see Table X1.1.notched tensile strength (NTS)the maximum nominal (net section) stress that a notched tensile specimen is capable ofsustaining. (E1823)process
21、a defined event or sequence of events in plating or coating that may include pretreatments and posttreatments.reaction hydrogen embrittlement (RHE) irreversible embrittlement caused by the reaction of hydrogen with metal to form astable hydride.residual stressstress in a metal in the absence of exte
22、rnal forces.sharp-notch strengththe maximum nominal (net section) stress that a sharply notched specimen is capable of sustaining.(E1823)straindeformation of a material caused by the application of an external force. (D4848)strain ratethe rate of relative length deformation with time due to an appli
23、ed stress. (C904)stressthe resistance to deformation developed within a material subjected to an external force. (D4848)stress concentration factor (kt)the ratio of the greatest stress in the region of a notch or other stress concentrator, as determinedby the theory of elasticity or by experimental
24、procedures that give equivalent values, to the corresponding nominal stress.(E1823)F2078 152stress corrosion cracking (SCC)a cracking process that requires the simultaneous action of a corrodent and sustained tensilestress.DISCUSSIONThis excludes corrosion-reduced sections that fail by fast fracture
25、. It also excludes intercrystalline or transcrystalline corrosion, which can disintegratean alloy without either applied or residual stress (G15). In essence the process of SCC and EAC are equivalent.stressintensity factor, Kthe magnitude of the mathematically ideal cracktip stress field (stress fie
26、ld singularity) for aparticular mode in a homogeneous linearelastic body. (E1823)DISCUSSIONKI=for a Mode I (opening mode) loading condition that displaces the crack faces in a direction normal to the crack plane.KII=for a Mode II (sliding mode) loading condition where the crack faces are displaced i
27、n shear sliding in the crack plane and in the primary crackpropagation direction.KIII=for a Mode III (tearing mode) loading condition where the crack faces are displaced in shear tearing in the crack plane but normal to the primarycrack propagation direction.susceptibility to hydrogen embrittlement
28、is a material property that is measured by the threshold stress intensity parameterfor hydrogen induced stress cracking, KIscc, KIHE , or KEHE, which is a function of hardness and microstructure.threshold (th)a point, separating conditions that will produce a given effect, from conditions that will
29、not produce the effect;the lowest load at which subcritical cracking can be detected.threshold stress (th) a stress below which no hydrogen stress cracking will occur and above which time-delayed fracture willoccur.threshold stress intensity (Kth)a stress intensity below which no hydrogen stress cra
30、cking will occur and above which,time-delayed fracture will occur.time-delayed embrittlementsee internal hydrogen embrittlement.4.2 Symbols:Papplied loadPc critical load required to rupture a specimen using a continuous loading ratePi crack initiation load for a given loading and environmental condi
31、tion using an incrementally increasing load underdisplacement controlPth threshold load in which Pi is invariant with respect to loading rate; Pth is the basis for calculating the threshold stress or thethreshold stress intensityapplied stressnetnet stress based on area at minimum diameter of notche
32、d round baristress at crack initiationth-IHEthreshold stresstest conducted in airgeometry dependentth-EHEthreshold stresstest conducted in a specified environmentgeometry dependentKstress-intensity factorKth threshold stress intensityKt stress concentration factorKIscc threshold stress intensity for
33、 stress corrosion crackingKIHE threshold stress intensity for IHEKEHE threshold stress intensity for EHERsb ratio of specimen crack strength to yield strength in bendingRnsb ratio of specimen notched strength to yield strength in bendingF2078 153ththresholdththreshold stress4.3 Abbreviations:EACenvi
34、ronmentally assisted crackingEHEenvironmental hydrogen embrittlementETULextended time under loadGHEgaseous hydrogen embrittlementHASChydrogen-assisted stress crackingHSChydrogen stress crackingHsrhydrogen susceptibility ratioIHEinternal hydrogen embrittlementHEhydrogen embrittlementNFS(B)notched fra
35、cture strength in bendingNFS(T)notched fracture strength in tensionNTSnotched tensile strengthISLincremental step loadISLththreshold from an incremental step-load testRAreduction of areaRHEreaction hydrogen embrittlementSCCstress corrosion crackingSCEsaturated calomel electrodeSLTsustained load test
36、ANNEX(Mandatory Information)A1. DEFINITIONS OF SYMBOLIC EXPRESSIONSA1.1 The following abbreviations and symbols are included as separate sections in this standard because they evolved specificallyfrom tests conducted on fasteners, which inherently have all of the ingredients necessary to create hydr
37、ogen embrittlementproblems.A1.2 Fasteners are generally (1) a notched, high-strength structural element that in service is always torqued to a high percentageof the fracture strength, (2) chemically cleaned, (3) coated with a sacrificial anodic coating that is generally electrochemicallydeposited pr
38、oducing a hydrogen charging condition, and (4) placed in service under cathodic charging conditions when exposedto an aqueous environmentall of the conditions necessary to cause classical hydrogen embrittlement (IHE) or environmentallyinduced hydrogen embrittlement (EHE).A1.3 Test Methods E8 Loading
39、 RatesThese results are independent of any residual hydrogen concentration because the testsare performed at a rate that does not allow sufficient time for the diffusion of hydrogen to occur.A1.3.1 Tensile Test Symbols:TS(T) = tensile strength (tension), ksi; calculated from the minimum specified te
40、nsile strength (mst) and minor diameter of thefastener.F2078 154FS(T) = fracture strength (tension), ksi; calculated from the measured fracture or ultimate tensile load of the fastener, or notchedor precracked test sample.Rnst = notched strength ratio in tension; calculated from FS(T)/TS(T).A1.3.2 B
41、end Test Symbols:YS(B) = TS(T).FS(B) = fracture strength (bend), ksi; calculated from the measured fracture or ultimate bend of the fastener, or notched orprecracked test sample.Rnsb = notched strength ratio in bending.A1.4 Test Method F1624 Loading RatesThese abbreviations are used for the terms fo
42、r results that are dependent on the residualhydrogen concentration. The tests are performed at a rate that allows sufficient time for the diffusion of hydrogen to occur.A1.4.1 ISLincremental step-load test to measure the threshold stress, which is slow enough to allow for the diffusion ofhydrogen to
43、 occur.A1.4.2 th-air(T/B) the threshold stress at a given loading rate measured in air in either tension or bend.A1.4.3 th-V(T/B) the threshold stress at a given loading rate measured at a given cathodic potential in either tension or bend.A1.4.4 th-H+(T/B)the lower limit of the threshold stress at
44、an invariant loading rate measured in the most aggressive hydrogencharging environment of -1.2V versus SCE in either tension or bend.A1.5 Evaluation Parameter:A1.5.1 %FS(T/B)degradation factor = % fracture strength.A1.5.2 Hsr(T/B)hydrogen susceptibility ratio, a material property that is a function
45、of composition, melting practice,thermomechanical processing, heat treatment, and much more sensitive to microstructure than Test Methods E8 mechanicalproperties.A1.5.3 Hsr(t/b)-IHE the threshold notched hydrogen susceptibility ratio in either tension or bend for internal hydrogenembrittlement, (IHE
46、).A1.5.4 Hsr(t/b)-EHE the threshold notched hydrogen susceptibility ratio in either tension or bend at a given cathodic potential forexternal or environmental hydrogen embrittlement, (EHE).A1.5.5 Hsr(t/b)-1.2V the lower limit threshold notched hydrogen susceptibility ratio in either tension or bend
47、for hydrogen-induced stress cracking in the most aggressive hydrogen charging environment of -1.2V versus SCE.F2078 155APPENDIX(Nonmandatory Information)X1. IHE/EHE COMPARISON CHARTBIBLIOGRAPHYThe following documents and publications may provide additional definitions or terminology in the field of
48、hydrogen em-brittlement.(1) Raymond, L., Ed., Hydrogen Embrittlement Testing, ASTM STP 543, ASTM, West Conshohocken, PA, 1972.(2) Raymond, L., Ed., Hydrogen Embrittlement: Prevention and Control, ASTM STP 962, ASTM, West Conshohocken, PA, 1988 .(3) “The Susceptibility of Fasteners to Hydrogen Embrit
49、tlement and Stress Corrosion Cracking,” Handbook of Bolts and Bolted Joints, Marcel Decker,Inc., New York, 1998, Chap. 39, p. 723.(4) ASTM Dictionary of Engineering Science or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ X1.1 Similarities/Differences Between Internal (IHE) and Envi
