1、Designation: G98 02 (Reapproved 2009)G98 17Standard Test Method forGalling Resistance of Materials1This standard is issued under the fixed designation G98; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.A
2、number in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory test which ranks the galling resistance of material couples. Most galling studies havebeen conducted
3、 on bare metals and alloys; however, non-metallics, coatings, and surface modified alloys may also be evaluatedby this test method.1.2 This test method is not designed for evaluating the galling resistance of material couples sliding under lubricated conditionsbecause galling usually will not occur
4、under lubricated sliding conditions using this test method.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health and healthenvironmental practices
5、and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommen
6、dations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2G40E177 Terminology Relating to Wear and ErosionPractice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory St
7、udy to Determine the Precision of a Test MethodG83 Test Method for Wear Testing with a Crossed-Cylinder Apparatus (Withdrawn 2005)33. Terminology3.1 Definitions:3.1.1 gallinga form of surface damage arising between sliding solids, distinguished by macroscopic, usually localized,roughening and creati
8、on of protrusions above the original surface; it often includes plastic flow or material transfer, or both.3.1.1.1 DiscussionThe onset of galling usually requires that the contact pressure exceeds some threshold value. Galling can be a precursor to seizingor loss of function. The identification of g
9、alling is somewhat subjective, and complete agreement does not exist, even amongexperts. G403.2 Definitions of Terms Specific to This Standard:3.2.1 threshold galling stressthe stress midway between the highest non-galled stress and the lowest galled stress asdetermined by this test method.4. Summar
10、y of Test Method4.1 This test method uses available laboratory equipment capable of maintaining a constant, compressive load between two flatspecimens, such as hydraulic or screw feed compression testing machines. One specimen is slowly rotated one revolution 360relative to the other specimen. The s
11、urfaces are examined for galling after sliding. The criterion for whether galling occurs is the1 This test method is under the jurisdiction ofASTM Committee G02 on Wear and Erosion and is the direct responsibility of Subcommittee G02.40 on Non-Abrasive Wear.Current edition approved Oct. 1, 2009July
12、15, 2017. Published February 2010August 2017. Originally approved in 1989. Last previous edition approved in 20022009 asG98G98 02 (2009).02. DOI: 10.1520/G0098-02R09.10.1520/G0098-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.o
13、rg. 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 only to provide the user of an ASTM st
14、andard 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 versionof the standard as published by A
15、STM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1appearance of the specimens based on unassisted visual examination. If the specimens have not galled, a new set of specimens istested at inc
16、reased load. This process is continued until galling occurs.4.2 Appropriate load intervals are chosen to determine the threshold galling stress within an acceptable range.4.3 The higher the threshold galling stressing, the more galling resistant is the test couple.5. Significance and Use5.1 This tes
17、t method is designed to rank material couples in their resistance to the failure mode caused by galling and not merelyto classify the surface appearance of sliding surfaces.5.2 This test method should be considered when damaged (galled) surfaces render components non-serviceable. Experience hasshown
18、 that galling is most prevalent in sliding systems that are slow moving and operate intermittently. The galling and seizureof threaded components is a classic example which this test method most closely simulates.5.3 Other galling-prone examples include: sealing surfaces of value trim which may leak
19、 excessively due to galling; and pumpwear rings that may function ineffectively due to galling.5.4 If the equipment continues to operate satisfactorily and loses dimension gradually, then mechanical wear should beevaluated by a different test such as the crossed cylinder Test Method (see Test Method
20、 G83). Chain belt pins and bushings areexamples of this type of problem.5.5 This test method should not be used for quantitative or final design purposes since many environmental factors influencethe galling performance of materials in service. Lubrication, alignment, stiffness and geometry are only
21、 some of the factors thatcan affect how materials perform. This test method has proven valuable in screening materials for prototypical testing that moreclosely simulates actual service conditions.6. Apparatus6.1 Commonly available laboratory equipment has been used to conduct galling tests. Both Br
22、inell hardness testers andservo-hydraulic testing machines have proven to be satisfactory as loading devices. Any apparatus that can apply and maintain aconstant compressive load should be acceptable.7. Test Specimens7.1 This test method uses a cylindrical flat-on-flat geometry. One specimen is call
23、ed the button (or pin) and is generally (butnot necessarily) rotated about its axis on the flat specimen called the block.7.2 Some typical button geometries are shown in Fig. 1.7.3 The only critical dimension is diameter “B of the contact area. The 6.4-mm (0.25-in.) diameter hole accommodates a ball
24、bearing for alignment purposes during the test. All other dimensions may be varied to the users convenience.7.4 The block specimen must have sufficient area to accommodate at least one test; however, most users have found that blocksof length 76 mm (3 in.) to 152 mm (6 in.) are ideal for multiple te
25、sts. A reasonable width is 19 mm (0.75 in.). Thickness is notcritical. Tests have been successfully run on blocks with thicknesses from 1.5 mm (0.06 in.) to 25.4 mm (1 in.).7.5 Maintain block flatness at 0.33 mm/m (0.004 in./ft).Metric Equivalentsin. mm in. mm14 6.4 58 1638 10 34 1912 13 78 220.500
26、0.003 12.7 0.08 118 29FIG. 1 Typical Button GeometriesG98 1727.6 The arithmetic average surface finish of both test surfaces should be between 0.25 and 1.1 m (10 and 45 in.). Leavespecimens as-ground or polished with abrasive paper to achieve the finish.8. Procedure8.1 An overall view of the galling
27、 test set-up is shown in Fig. 2.8.2 CleaningImmediately prior to testing, clean the test surfaces of the specimens using a procedure that will remove anyscale, oil film, or foreign matter. The following cleaning technique is suggested for metallic specimens: clean the button and blockin trichloroeth
28、ane, ultrasonically, if possible; a methanol rinse may be used to remove any traces of trichloroethane residue (seeNote 1). Materials with open grains (some powder metals) must be dried to remove all traces of the cleaning solvent which maybe entrapped in the material. Demagnetize steel specimens ha
29、ving residual magnetism.NOTE 1This cleaning procedure is not appropriate for polymers. If a polymer is being tested, a cleaning procedure that does not alter the chemistryor surface should be determined.8.3 Mount specimens in the loading device and degrease again if possible. Lightly load the specim
30、ens. Twist the button by handto make sure it is seated flat on the block.8.4 Apply the selected load. If there is no estimate of the galling resistance of the test couple, it is advisable to start with 890N (200 lb) and increase the stress in subsequent tests as desired. This will minimize damage to
31、 the specimens so that they maybe remachined and used for further testing.8.5 Immediately rotate one specimen (usually the button, but not necessarily) one revolution. Use an open-end wrench,adjustable wrench, or some other special tool in order to grip the specimen for rotating by hand. A mechanize
32、d system may alsobe used to rotate one specimen relative to the other. This may allow torque measurement during testing which may provide usefuldata on incipient scoring.8.6 Actual sliding time should be between 3 to 20 s. Stopping for regripping the turning tool is permitted, but this elapsed timei
33、s not counted in the 3 to 20 s test time.8.7 Release the load.8.8 Examine both specimens for galling. If the specimens appear smooth and undamaged (burnishing does not constitutedamage) to the unaided eye, repeat the procedure at a higher load with untested specimens.8.9 If the surfaces exhibit scra
34、tch marks, this is not galling. A wavy surface is not considered galled. At least one of thecontacting surfaces must exhibit torn metal for galling to have occurred. If fracture of any cold welded areas has taken place inthe plane of the surfaces and no distinct raised metal (protrusion) is found, g
35、alling has not occurred for the purposes of this testmethod.8.10 If galling has occurred even on just one specimen, test at a lower load to establish an interval between the highestnon-galled stress and the galled stress. This interval should be no greater than 34.5 MPa (5 ksi) for threshold galling
36、 stresses greaterthan 138 MPa (20 ksi) and no greater than 21 MPa (3 ksi) for stresses 138 MPa (20 ksi) or less.8.11 If galling is questionable or borderline, repeat at a higher load to confirm the previous test stress.8.12 A typical series of test specimens is shown in Fig. 3.8.13 Calculate the thr
37、eshold galling stress as the stress midway between the highest non-galled test and the lowest galled test.Use the original diameter of the button to calculate the contact stress. Assume full contact of the button diameter even though insome lightly loaded tests, this may not always be the case.FIG.
38、2 Schematic Diagram of Galling Test Set-UpG98 1739. Report9.1 The following data should be included in the test report:9.1.1 Composition and hardness of specimens,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 surfac
39、e finish, preparation, and cleaning technique,9.1.5 Any unusual event during the test, for example, buckling of the button,9.1.6 Mechanical test system used, such as mechanical or hydraulic, type, size, and9.1.7 Temperature, humidity, atmosphere.10. Precision and Bias410.1 The subjective determinati
40、on of the threshold galling stress by visual examination of surfaces makesprecision of this testmethod is based on an interlaboratory study of Test Method G98it difficult to have high precision in test results from differentlaboratories. However, to minimize subjectivity, several examples of tested
41、specimens are shown for guidance in, conducted in2016. Four laboratories participated in this study. Each of the four labs reported duplicate test results for a single type of stainlesssteel. Every “test result” reported represents an individual determination. Except for the use Fig. 4. This may not
42、 be a seriousdrawback since experience hasof only four laboratories and a single material type, Practice E691 shown that large differences inthe order of 34.5 to 69.0 MPa (5 to 10 ksi) are necessary to achieve noticeable improvements in service.was followed for the designand analysis of the data; th
43、e details given in ASTM Research Report No. G02-1017.10.1.1 Repeatability (r)The difference between repetitive results obtained by the same operator in a given laboratory applyingthe same test method with the same apparatus under constant operating conditions on identical test material within short
44、intervalsof time would in the long run, in the normal and correct operation of the test method, exceed the following values only in one casein 20.10.1.1.1 Repeatability can be interpreted as the maximum difference between two results, obtained under repeatabilityconditions, that is accepted as plaus
45、ible due to random causes under normal and correct operation of the test method.10.1.1.2 Repeatability limits are listed in Table 1 below.4 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:G02-1017. Contact ASTM CustomerService a
46、t serviceastm.org.Gall Buttons appear on top.Gall Block appears underneath.Contact Stress:MPa 131.7 169.6 247.5 193.0(ksi) 19.1 24.6 35.9 28.0Comment OK OK Galled OKNOTE 1Another test at 220.6 MPa (32 ksi) would be necessary to establish the threshold gall stress within acceptable limits.FIG. 3 Typi
47、cal Gall Test SeriesTABLE 1 Threshold Galling Stress (psi)Material AverageA Repeatability StandardDeviationReproducibility StandardDeviationRepeatability Limit Reproducibility Limitx sr sR r RType 303 StainlessSteel 29.85 MPa (4.330 ksi) 9.136 MPa (1.325 ksi) 11.59 MPa (1.682 ksi) 25.58 MPa (3.710 k
48、si) 32.46 MPa (4.709 ksi)AThe average of the laboratories calculated averages.FIG. 4 Test SpecimensG98 17410.1.2 Reproducibility (R)The difference between two single and independent results obtained by different operators applyingthe same test method in different laboratories using different apparat
49、us on identical test material would, in the long run, in thenormal and correct operation of the test method, exceed the following values only in one case in 20.10.1.2.1 Reproducibility can be interpreted as the maximum difference between two results, obtained under reproducibilityconditions, that is accepted as plausible due to random causes under normal and correct operation of the test method.10.1.2.2 Reproducibility limits are listed in Table 1 below.10.1.3 The above terms (repeatability limit and reproducibility limit) are used as specified in P
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