1、Designation: F 2078 01Standard Terminology Relating toHydrogen Embrittlement Testing1This standard is issued under the fixed designation F 2078; 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
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This terminology covers the principal terms, abbrevia-tions, and symbols relating to mechanical methods for hydro-gen embrittlement testing. Th
3、ese definitions are published toencourage uniformity of terminology in product specifications.2. Referenced Documents2.1 ASTM Standards:A 941 Terminology Relating to Steel, Stainless Steel, Re-lated Alloys, and Ferroalloys2E 6 Terminology Relating to Methods of Mechanical Test-ing3E 8 Test Methods f
4、or Tension Testing of Metallic Materials3E 812 Test Method for Crack Strength of Slow Bend,Precracked Charpy Specimens of High-Strength MetallicMaterials3E 1823 Terminology Relating to Fatigue and Fracture Test-ing3F 1624 Test Method for Measurement of Hydrogen Em-brittlement Threshold in Steel by t
5、he Incremental StepLoading Technique4G 15 Terminology Relating to Corrosion and CorrosionTesting53. 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 transferinform
6、ation adequately within the field.3.2 Some of the terms are defined in other terminologystandards, which are respectively identified in parenthesesfollowing the definition.4. Terminology4.1 Definitions:bakingheating to a temperature at least 50F below thetempering or aging temperature of the metal o
7、r alloy toremove hydrogen before embrittlement occurs by the forma-tion of microcracks.DISCUSSIONNo metallurgical changes take place as a result ofbaking. (A 941)brittlethe inability of a material to deform plastically beforefracturing.crack strengththe maximum value of the nominal stress thata crac
8、ked specimen is capable of sustaining. (E 1823)ductilethe ability of a material to deform plastically beforefracturing. (E 6)embrittleto make brittle; that is, to lose ductility.embrittlementthe loss of ductility or toughness of a metal oralloy. (G 15)environmental hydrogen embirttlement (EHE)genera
9、llycaused by hydrogen introduced into the steel from theenvironment after exposure to an externally applied stress.DISCUSSIONEmbrittlement as a result of hydrogen introduced intosteel from external sources while under stress. Tests are conducted in anenvironment. (STP 962)DISCUSSIONFound in plated p
10、arts that cathodically protect the metalfrom corroding. Generates hydrogen at the surface of the metal.Produces a clean, intergranular fracture surface. Not reversible. (Thesubtle differences between IHE and EHE are detailed in Appendix X1.)(STP 543)environmentally assisted cracking (EAC)generic, cr
11、ackgrowth as a result of exposure to the environment.fracture strengththe load at the beginning of fractureduring a tension test divided by the original cross-sectionalarea.gaseous hydrogen embrittlement (GHE)a distinct form ofEHE caused by the presence of external sources of highpressure hydrogen g
12、as; cracking initiates on the outersurface.heat treatmentheating to a temperature that produces met-allurgical changes in the steel that alter the mechanicalproperties and microstructure of the metal. (A 941)hydrogen-assisted stress cracking (HASC)crack growth asa result of the presence of hydrogen;
13、 it can be either IHE orEHE and sometimes is referred to as hydrogen stresscracking (HSC).hydrogen embrittlementa permanent loss of ductility in ametal or alloy caused by hydrogen in combination withstress, either an externally applied or an internal residualstress. (G 15)1This terminology standard
14、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 May 10, 2001. Published July 2001.2Annual Book of ASTM Standards, Vol 01.01.3Annual Book of ASTM Standards, Vol 03.01.4An
15、nual Book of ASTM Standards, Vol 15.03.5Annual Book of ASTM Standards, Vol 03.02.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.hydrogen susceptibility ratio (Hsr)the ratio of the thresh-old for the onset of hydrogen assisted cracking to the tensilestrength o
16、f the material.internal hydrogen embrittlement (IHE)hydrogen em-brittlement caused by absorbed atomic hydrogen from anychemical process that introduces hydrogen into the steelbefore exposure to an externally applied stress.DISCUSSIONEmbrittlement results from the formation of microc-racks with time
17、and is often referred to as “time-delayed embrittle-ment.” Once microcracks have been formed, ductility cannot berestored. Tests are generally conducted in air. (STP 543)DISCUSSIONThis type of embrittlement is referred to as the classictype of hydrogen embrittlement in steel, although IHE has also b
18、eenobserved in a wide variety of other materials including nickel basealloys and austenitic stainless steels provided that they are severelycharged with hydrogen. (STP 543)DISCUSSIONFor steels, IHE is most severe at room temperature. Theproblem primarily results from electroplating. Other sources of
19、 hydro-gen are the processing treatments, such as melting and pickling.(STP 543)notched tensile strengththe maximum nominal (net sec-tion) stress that a notched tensile specimen is capable ofsustaining. (E 1823)processa defined event or sequence of events in plating orcoating that may include pretre
20、atments and posttreatments.reaction hydrogen embrittlement (RHE)hydrogen canreact with itself, with the matrix, or with a foreign elementin the matrix and form new phases that are usually quitestable, and embrittlement is not reversible.DISCUSSIONQuite distinct from the other types in that the hydro
21、genmay react near the surface or diffuse a substantial distance before itreacts. (STP 543)sharp-notch strengththe maximum nominal (net section)stress that a sharply notched specimen is capable of sustain-ing. (E 1823)stress corrosion cracking (SCC)a cracking process thatrequires the simultaneous act
22、ion of a corrodent and sustainedtensile stress.DISCUSSIONThis excludes corrosion-reduced sections that fail byfast fracture and intercrystalline or transcrystalline corrosion, whichdisintegrate an alloy without either applied or residual stress. (G 15)DISCUSSIONConsidered to occur while under anodic
23、 polarization.Not reversible. Produces an oxidized, intergranular fracture surface.(STP 543)stressintensity factor, K, KI,KII,KIII,the magnitude ofthe ideal cracktip stress field (stress field singularity) for aparticular mode in a homogeneous linearelastic body.(E 1823)susceptibility to hydrogen em
24、brittlementis a materialproperty that is measured by the threshold stress intensityparameter for hydrogen induced stress cracking, KIscc,KIHE,or KEHE, which is a function of hardness and microstructure.threshold (th)a point separating conditions that will producea given effect from conditions that w
25、ill not produce theeffect; the lowest load at which subcritical cracking can bedetected.threshold stress (sth)a stress below which no hydrogenstress cracking will occur and above which time-delayedfracture will occur; in Test Method F 1624, the threshold isidentified as the maximum load at the onset
26、 of cracking thatcuases a 5 % drop in load of NSF(B)F1624under displace-ment control.threshold stress intensity (Kth)a stress intensity belowwhich no hydrogen stress cracking will occur and abovewhich, time-delayed fracture will occur.4.2 Symbols:Papplied loadPccritical load required to rupture a sp
27、ecimen using acontinuous loading ratePicrack initiation load for a given loading and environmentalcondition using an incrementally increasing load underdisplacement controlPththreshold load in which Piis invariant with respect toloading rate; Pthis the basis for calculating the thresholdstress or th
28、e threshold stress intensitysapplied stresssnetnet stress based on area at minimum diameter of notchedround barsistress at crack initiationsth-IHEthreshold stresstest conducted in airgeometrydependentsth-EHEthreshold stresstest conducted in a specifiedenvironmentgeometry dependentRsbratio of specime
29、n crack strength to yield strength inbendingRnsbratio of specimen notched strength to yield strength inbendingKIsccthreshold stress intensity for stress corrosion crackingKIHEthreshold stress intensity for IHEKEHEthreshold stress intensity for EHE4.3 Abbreviations:NFS(B)notched fracture strength in
30、bendingNFS(T)notched fracture strength in tensionNFS(B)F1624notched fracture strength in bending of a barespecimen at Test Method F 1624 step-loading ratesISLincremental step loadISLththreshold from an incremental step-load testF 20782ANNEX(Mandatory Information)A1. DEFINITIONS OF SYMBOLIC EXPRESSIO
31、NSA1.1 The following abbreviations and symbols are in-cluded as separate sections in this standard because theyevolved specifically from tests conducted on fasteners, whichinherently have all of the ingredients necessary to createhydrogen embrittlement problems.A1.2 Fasteners are generally (1) a not
32、ched, high-strengthstructural element that in service is always torqued to a highpercentage of the fracture strength, (2) chemically cleaned, (3)coated with a sacrificial anodic coating that is generallyelectrochemically deposited producing a hydrogen chargingcondition, and (4) placed in service und
33、er cathodic chargingconditions when exposed to an aqueous environmentall ofthe conditions necessary to cause classical hydrogen embrittle-ment (IHE) or environmentally induced hydrogen embrittle-ment (EHE).A1.3 Test Methods E 8 Loading RatesThese results areindependent of any residual hydrogen conce
34、ntration becausethe tests are performed at a rate that does not allow sufficienttime for the diffusion of hydrogen to occur.A1.3.1 Tensile Test Symbols:TS(T) = tensile strength (tension), ksi; calculated from theminimum specified tensile strength (mst) and minor diameterof the fastener=4Pmst/p dmino
35、r2; Ex: SAE J1237/M10 =TS(T)=4(Pmst= 12 120)/p (dminor= 0.3285)2= 143 ksiFS(T) = fracture strength (tension), ksi; calculated from themeasured fracture or ultimate tensile load of the fastener, ornotched or precracked test sample = Pult/net area FS(T)=4Pult/p dminor2 $ TS(T)Rnst= notched strength ra
36、tio in tension; calculated fromFS(T)/TS(T) = Rnst# 1.5A1.3.2 Bend Test Symbols:YS(B) = TS(T), which for M10 = 143 ksi; andPys(B) = TS(T) p d3/256 = 143 p (0.32853)/256 = 62lbs, or d PTS(T)/64 = (0.3285) (12 120 lbs)/64 = 62 lbs; orFS(B) = fracture strength (bend), ksi; calculated from themeasured fr
37、acture or ultimate bend of the fastener, or notchedor precracked test sample; that is, FS(B) = 256 Pmeasuredbend/(p dminor3)Rnsb= notched strength ratio in bending: Ref: Test MethodE 812; calculated from FS(B)/TS(T) = Rnsb# 2.3A1.4 Test Method F 1624 Loading RatesThese abbrevia-tions are used for th
38、e terms for results that are dependent on theresidual hydrogen concentration. The tests are performed at arate that allows sufficient time for the diffusion of hydrogen tooccur.A1.4.1 ISLincremental step-load test to measure thethreshold stress per Test Method F 1624, which is slow enoughto allow fo
39、r the diffusion of hydrogen to occurA1.4.2 sth-air(T/B)the threshold stress at a given loadingrate measured in air per Test Method F 1624 in either tensionor bendA1.4.3 sth-V(T/B)the threshold stress at a given loadingrate measured at a given cathodic potential per Test MethodF 1624 in either tensio
40、n or bendA1.4.4 sth-H+(T/B)the lower limit of the threshold stress atan invariant loading rate measured in the most aggressivehydrogen charging environment of -1.2V versus SCE per TestMethod F 1624 in either tension or bendA1.5 Evaluation Parameter:A1.5.1 %FS(T/B)degradation factor = % fracture stre
41、ngthcalculated from %FS(T/B) = Hsr(T/B)/Rns(t/b)3 100 % = sth-H+(T/B)/FS(T/B) or the percentage degradation in strength asmeasured by the ratio of the worst case or minimum thresholdvalue divided by the maximum attainable strength in airA1.5.2 Hsr(T/B)hydrogen susceptibility ratio = sth-H+(T/B)/TS(T
42、); a material property that is a function of composition,melting practice, thermomechanical processing, heat treatment,and much more sensitive to microstructure than Test MethodsE 8 mechanical propertiesA1.5.3 Hsr(t/b)-IHEthe threshold notched hydrogen suscep-tibility ratio in either tension or bend
43、 for internal hydrogenembrittlement, IHE, which is given by Hsr(t/b)-IHE= sth-air(T/B) + TS(T)A1.5.4 Hsr(t/b)-EHEthe threshold notched hydrogen suscep-tibility ratio in either tension or bend at a given cathodicpotential for external or environmental hydrogen embrittle-ment, EHE, which is given by H
44、sr(t/b)-EHE= sth-V(T/B)+ TS(T)A1.5.5 Hsr(t/b)-1.2Vthe lower limit threshold notched hy-drogen susceptibility ratio in either tension or bend forhydrogen-induced stress cracking in the most aggressive hy-drogen charging environment of -1.2V versus SCE, which isgiven byA1.5.6 Hsr(T/B)Hsr(t/b) -1.2V= s
45、th-H+(T/B)+ TS(T) =Hsr(T/B)F 20783APPENDIX(Nonmandatory Information)X1. IHE/EHE COMPARISON CHARTBIBLIOGRAPHYThe following documents and publications may provide additional definitions or terminology in the field of hydrogenembrittlement.(1) Raymond, L., Ed., Hydrogen Embrittlement Testing, ASTM STP5
46、43, ASTM, West Conshohocken, PA, 1972.(2) Raymond, L., Ed., Hydrogen Embrittlement: Prevention and Con-trol, ASTM STP 962, ASTM, West Conshohocken, PA, 1988.(3) “The Susceptibility of Fasteners to Hydrogen Embrittlement andStress Corrosion Cracking,” Handbook of Bolts and Bolted Joints,Marcel Decker
47、, Inc., New York, 1998, Chap. 39, p. 723.The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connectionwith any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of an
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