1、Designation: G 98 02Standard Test Method forGalling Resistance of Materials1This standard is issued under the fixed designation G 98; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A number in parenthese
2、s indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory test which ranksthe galling resistance of material couples. Most galling studieshave been conducted on bare metals an
3、d alloys; however,non-metallics, coatings, and surface modified alloys may alsobe evaluated by this test method.1.2 This test method is not designed for evaluating thegalling resistance of material couples sliding under lubricatedconditions because galling usually will not occur under lubri-cated sl
4、iding conditions using this test method.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory
5、limitations prior to use.2. Referenced Documents2.1 ASTM Standards:G40 Terminology Relating to Wear and Erosion2G83 Test Method for Wear Testing with a Crossed-CylinderApparatus23. Terminology3.1 Definition: Definition used in this test method is given inTerminology G 40.3.1.1 gallinga form of surfa
6、ce damage arising betweensliding solids, distinguished by macroscopic, usually localized,roughening and creation of protrusions above the originalsurface; it often includes plastic flow or material transfer, orboth.3.1.1.1 DiscussionThe onset of galling usually requiresthat the contact pressure exce
7、eds some threshold value. Gallingcan be a precursor to seizing or loss of function. The identifi-cation of galling is somewhat subjective, and complete agree-ment does not exist, even among experts.3.2 Definitions of Terms Specific to This Standard:3.2.1 threshold galling stressthe stress midway bet
8、weenthe highest non-galled stress and the lowest galled stress asdetermined by this test method.4. Summary of Test Method4.1 This test method uses available laboratory equipmentcapable of maintaining a constant, compressive load betweentwo flat specimens, such as hydraulic or screw feed compres-sion
9、 testing machines. One specimen is slowly rotated onerevolution 360 relative to the other specimen. The surfaces areexamined for galling after sliding. The criterion for whethergalling occurs is the appearance of the specimens based onunassisted visual examination. If the specimens have notgalled, a
10、 new set of specimens is tested at increased load. Thisprocess is continued until galling occurs.4.2 Appropriate load intervals are chosen to determine thethreshold galling stress within an acceptable range.4.3 The higher the threshold galling stressing, the moregalling resistant is the test couple.
11、5. Significance and Use5.1 This test method is designed to rank material couples intheir resistance to the failure mode caused by galling and notmerely to classify the surface appearance of sliding surfaces.5.2 This test method should be considered when damaged(galled) surfaces render components non
12、-serviceable. Experi-ence has shown that galling is most prevalent in slidingsystems that are slow moving and operate intermittently. Thegalling and seizure of threaded components is a classicexample which this test method most closely simulates.5.3 Other galling-prone examples include: sealing surf
13、acesof value trim which may leak excessively due to galling; andpump wear rings that may function ineffectively due to galling.5.4 If the equipment continues to operate satisfactorily andloses dimension gradually, then mechanical wear should beevaluated by a different test such as the crossed cylind
14、er TestMethod (see Test Method G83). Chain belt pins and bushingsare examples of this type of problem.5.5 This test method should not be used for quantitative orfinal design purposes since many environmental factors influ-ence the galling performance of materials in service. Lubrica-tion, alignment,
15、 stiffness and geometry are only some of thefactors that can affect how materials perform. This test method1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.40 on Non-Abrasive Wear.Current edition approved Nov. 1
16、0, 2002. Published January 2003. Originallyapproved in 1989. Last previous edition approved in 1996 as G 98 91 (1996).2Annual Book of ASTM Standards, Vol 03.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.has proven valuable in sc
17、reening materials for prototypicaltesting that more closely simulates actual service conditions.6. Apparatus6.1 Commonly available laboratory equipment has beenused to conduct galling tests. Both Brinell hardness testers andservo-hydraulic testing machines have proven to be satisfac-tory as loading
18、devices. Any apparatus that can apply andmaintain a constant compressive load should be acceptable.7. Test Specimens7.1 This test method uses a cylindrical flat-on-flat geometry.One specimen is called the button (or pin) and is generally (butnot necessarily) rotated about its axis on the flat specim
19、encalled the block.7.2 Some typical button geometries are shown in Fig. 1.7.3 The only critical dimension is diameter “B of thecontact area. The 6.4-mm (0.25-in.) diameter hole accommo-dates a ball bearing for alignment purposes during the test. Allother dimensions may be varied to the users conveni
20、ence.7.4 The block specimen must have sufficient area to accom-modate at least one test; however, most users have found thatblocks of length 76 mm (3 in.) to 152 mm (6 in.) are ideal formultiple tests. A reasonable width is 19 mm (0.75 in.).Thickness is not critical. Tests have been successfully run
21、 onblocks with thicknesses from 1.5 mm (0.06 in.) to 25.4 mm (1in.).7.5 Maintain block flatness at 0.33 mm/m (0.004 in./ft).7.6 The arithmetic average surface finish of both test sur-faces should be between 0.25 and 1.1 m (10 and 45 in.).Leave specimens as-ground or polished with abrasive paper toac
22、hieve the finish.8. Procedure8.1 An overall view of the galling test set-up is shown inFig. 2.8.2 CleaningImmediately prior to testing, clean the testsurfaces of the specimens using a procedure that will removeany scale, oil film, or foreign matter. The following cleaningtechnique is suggested for m
23、etallic specimens: clean the buttonand block in trichloroethane, ultrasonically, if possible; amethanol rinse may be used to remove any traces of trichlo-roethane residue.3Materials with open grains (some powdermetals) must be dried to remove all traces of the cleaningsolvent which may be entrapped
24、in the material. Demagnetizesteel specimens having residual magnetism.8.3 Mount specimens in the loading device and degreaseagain if possible. Lightly load the specimens. Twist the buttonby hand to make sure it is seated flat on the block.8.4 Apply the selected load. If there is no estimate of thega
25、lling resistance of the test couple, it is advisable to start with890 N (200 lb) and increase the stress in subsequent tests asdesired. This will minimize damage to the specimens so thatthey may be remachined and used for further testing.8.5 Immediately rotate one specimen (usually the button,but no
26、t necessarily) one revolution. Use an open-end wrench,adjustable wrench, or some other special tool in order to gripthe specimen for rotating by hand. A mechanized system mayalso be used to rotate one specimen relative to the other. Thismay allow torque measurement during testing which mayprovide us
27、eful data on incipient scoring.8.6 Actual sliding time should be between 3 to 20 s.Stopping for regripping the turning tool is permitted, but thiselapsed time is not counted in the 3 to 20 s test time.8.7 Release the load.8.8 Examine both specimens for galling. If the specimensappear smooth and unda
28、maged (burnishing does not constitutedamage) to the unaided eye, repeat the procedure at a higherload with untested specimens.8.9 If the surfaces exhibit scratch marks, this is not galling.A wavy surface is not considered galled. At least one of thecontacting surfaces must exhibit torn metal for gal
29、ling to haveoccurred. If fracture of any cold welded areas has taken placein the plane of the surfaces and no distinct raised metal(protrusion) is found, galling has not occurred for the purposesof this test method.8.10 If galling has occurred even on just one specimen, testat a lower load to establ
30、ish an interval between the highestnon-galled stress and the galled stress. This interval should be3This cleaning procedure is not appropriate for polymers. If a polymer is beingtested, a cleaning procedure that does not alter the chemistry or surface should bedetermined.Metric Equivalentsin. mm in.
31、 mm14 6.458 1638 1034 1912 1378 220.500 6 0.003 12.7 6 0.08 118 29FIG. 1 Typical Button GeometriesFIG. 2 Schematic Diagram of Galling Test Set-UpG98022no greater than 34.5 MPa (5 ksi) for threshold galling stressesgreater than 138 MPa (20 ksi) and no greater than 21 MPa (3ksi) for stresses 138 MPa (
32、20 ksi) or less.8.11 If galling is questionable or borderline, repeat at ahigher load to confirm the previous test stress.8.12 A typical series of test specimens is shown in Fig. 3.8.13 Calculate the threshold galling stress as the stressmidway between the highest non-galled test and the lowestgalle
33、d test. Use the original diameter of the button to calculatethe contact stress. Assume full contact of the button diametereven though in some lightly loaded tests, this may not alwaysbe the case.9. Report9.1 The following data should be included in the test report:9.1.1 Composition and hardness of s
34、pecimens,9.1.2 Thermal history of specimens,9.1.3 Threshold galling stress for test couples, interval used,and rotation time,9.1.4 Initial surface finish, preparation, and cleaning tech-nique,9.1.5 Any unusual event during the test, for example,buckling of the button,9.1.6 Mechanical test system use
35、d, such as mechanical orhydraulic, type, size, and9.1.7 Temperature, humidity, atmosphere.10. Precision and Bias10.1 The subjective determination of the threshold gallingstress by visual examination of surfaces makes it difficult tohave high precision in test results from different laboratories.Howe
36、ver, to minimize subjectivity, several examples of testedspecimens are shown for guidance in Fig. 4. This may not bea serious drawback since experience has shown that largedifferences in the order of 34.5 to 69.0 MPa (5 to 10 ksi) arenecessary to achieve noticeable improvements in service.10.2 In in
37、terlaboratory testing, three laboratories reported athreshold galling stress of exactly 7 MPa (1 ksi) for self-matedAISI 316 stainless steel. In other tests, three laboratoriesreported stresses of over 360 MPa (52 ksi) without any gallingfor self-mated aluminum bronze.10.3 No rigorous statement can
38、be made regarding biassince there is no independent measure of galling resistance.11. Keywords11.1 button-on-block test; galling; galling resistance rank-ing; macroscopic surface damage; seized components; slidingmetallic surfaces; threshold galling stressGall ButtonsGall BlockContact Stress (MPa) (
39、ksi)131.719.1169.624.6247.535.9193.028.0Comment OK OK Galled OKNOTE 1Another test at 220.6 MPa (32 ksi) would be necessary toestablish the threshold gall stress within acceptable limits.FIG. 3 Typical Gall Test SeriesG98023ASTM International takes no position respecting the validity of any patent ri
40、ghts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at an
41、y time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments w
42、ill receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by A
43、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 4 Test SpecimensG98024
