1、Designation: G 196 08Standard Test Method forGalling Resistance of Material Couples1This standard is issued under the fixed designation G 196; 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 p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory test that ranks thegalling resistance of material couples using a quantitativemeasure. Bare metals, alloys, n
3、onmetallic materials, coatings,and surface modified materials may be evaluated by this testmethod.1.2 This test method is not designed for evaluating thegalling resistance of material couples sliding under lubricatedconditions, because galling usually will not occur underlubricated sliding condition
4、s using this test method.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 s
5、tandard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG98 Test Method for Galling Resistance of Materials3. Terminology3.1 Definition
6、s used in this test method given in Terminol-ogy G40.3.2 Definitions:3.2.1 apparent area of contactarea of contact betweentwo solid surfaces defined by the boundaries of their macro-scopic interface.3.2.2 gallingform of surface damage arising betweensliding solids, distinguished by macroscopic, usua
7、lly localized,roughening and creation of protrusions above the originalsurface; it often includes plastic flow or material transfer, orboth.3.2.3 triboelementone of two or more solid bodies thatcomprise a sliding, rolling, or abrasive contact, or a bodysubjected to impingement or cavitation. (Each t
8、riboelementcontains one or more tribosurfaces.)3.2.4 tribosurfacesany surface (of a solid body) that is inmoving contact with another surface or is subjected to im-pingement or cavitation.3.2.5 tribosystemany system that contains one or moretriboelements, including all mechanical, chemical, and envi
9、-ronmental factors relevant to the tribological behavior. (Seealso triboelement.)3.3 Definitions of Terms Specific to This Standard:3.3.1 galling50stress at which the probability of gallingoccurring on one or both of the test specimens is 50%.4. Summary of Test Method4.1 This test method uses availa
10、ble laboratory equipmentcapable of maintaining a constant, compressive load betweentwo flat specimens, such as hydraulic compression testingmachines. One specimen is slowly rotated one completerevolution relative to the other specimen. The surfaces areexamined for galling after sliding. The criterio
11、n for whethergalling occurs is the appearance of the specimens based onunassisted visual examination.4.2 Appropriate load intervals are chosen to determine thethreshold galling stress within an acceptable range.4.3 The higher the Galling50value, the more galling resis-tant is the test couple.1This t
12、est 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 July 1, 2008. Published August 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
13、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 Thi
14、s 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 has been shown to have higherrepeatability than Test Method G98in determining the gallingresistance. T
15、est Method G98can be used for initial ranking ofgalling resistance.5.3 This test method should be considered when damaged(galled) surfaces render components non-serviceable. Experi-ence has shown that galling is most prevalent in slidingsystems that are slow moving and operate intermittently. Thegal
16、ling and seizure of threaded components is a classicexample that this test method most closely simulates.5.4 Other galling-prone examples include: sealing surfacesof valves that may leak excessively due to galling and pumpwear rings that may function ineffectively due to galling.5.5 If the equipment
17、 continues to operate satisfactorily andloses dimension gradually, then galling is not present, and thewear should be evaluated by a different test method.5.6 This test method should not be used for quantitative orfinal design purposes, since many environmental factors influ-ence the galling perform
18、ance of materials in service. Lubrica-tion, alignment, stiffness, and geometry are only some of thefactors that can affect how materials perform. This test methodhas proven valuable in screening materials for prototypicaltesting that more closely simulates actual service conditions.6. Apparatus6.1 C
19、ommonly available laboratory equipment has beenused to conduct galling tests. Any apparatus that can apply andmaintain a constant compressive load should be acceptable.The use of a displacement controlled machines is generally notacceptable for this test because small variations in displace-ment of
20、the specimens leads to large changes in the appliedload.6.2 The alignment of the specimens is accomplished via thealignment pin shown in Fig. 1. This pin is readily fabricated bypress fit of a tooling ball into a drill rod or similar shaft with anappropriately sized hole machined into the end of the
21、 pin.Tooling balls are relatively inexpensive and readily availablefrom industrial suppliers.6.3 A hardened steel ball with a diameter of 9.53 mm isrequired for the testing procedure.7. Test Specimen7.1 This test method uses two concentric hollow cylindricalspecimens with the ends mated. This result
22、s in area contact inthe shape of an annulus. One specimen is rotated about its axisand the other is held fixed.7.2 A typical geometry of the specimen is shown in Fig. 2.7.3 The critical dimensions of the specimens are the12.70-mm outer diameter and the 6.375-mm hole. All otherdimensions may be varie
23、d to the users convenience. The hexshape shown on the specimen is not required, however, it doesprovide a convenient means of gripping the specimens duringtesting.7.4 A critical feature of the specimens is the flatness. Thecontact surface of the specimen shall be flat within 0.005 mmto ensure area c
24、ontact. Flatness can be measured using a dialindicator.8. Procedure8.1 An overall view of the galling test setup is shown in Fig.3.8.2 CleaningImmediately prior to testing, clean the testsurfaces of the new specimens using a procedure that willremove any scale, oil film, or foreign matter. The follo
25、wingcleaning technique is suggested for metallic specimens:8.2.1 Clean the specimens in an ultrasonic cleaner usingmild ultrasonic cleaning detergent and warm water for 10 min.8.2.2 Rinse the specimens thoroughly with water.8.2.3 Repeat this process using fresh solution.8.2.4 After the final cleanin
26、g, dry the specimens with alint-free wipe.8.2.5 Remove any spotting with acetone and a lint-freewipe.8.3 Mount the new specimens in the loading device. Lightlyload the specimens. Twist the specimens relative to each otherapproximately 45 to ensure proper seating of the wearsurfaces.8.4 Apply the sel
27、ected load and rotate one specimen onerevolution using an open-end wrench or other tool in order togrip the specimens. A mechanized system may also be used toFIG. 1 Geometry of Alignment Pin (all dimensions are in mm)G196082rotate one specimen relative to the other. This may allow torquemeasurement
28、during testing which may provide useful data onincipient scoring.8.5 Sliding time should be approximately 10 s. Stopping forre-gripping of the turning tool is permitted, but re-grippingshould minimized. The elapsed time to re-grip is not counted inthe 10 s test time.8.6 Release the load.8.7 Examine
29、both specimens for galling. A photograph oftypical galled specimens is shown in Fig. 4. If the specimensappear smooth and undamaged (burnishing does not constitutedamage) to the unaided eye then galling is said to not haveoccurred. If any galling is present, regardless of the magnitude,then galling
30、is said to be present. In this method, there are nodegrees of galling. Galling is said to either exist on the testspecimens or not. If the surfaces exhibit scratch marks, this isFIG. 2 Geometry of Specimen (all dimensions are in mm)FIG. 3 Schematic Diagram of Galling Test SetupG196083not galling. A
31、wavy surface is not considered galled. At leastone of the contacting surfaces shall exhibit torn metal forgalling to have occurred.8.8 A minimum of 12 replicates shall be tested at each loadlevel.8.9 Aminimum of four load levels shall be tested in order toperform the data analysis. At least two load
32、 levels shall beabove the load where 50% of the specimens would gall. Atleast two load levels shall be below the load where 50% of thespecimens would gall.8.10 At least two data points shall lie within the gallingfrequency range of 0.2 to 0.8, or one data point within thegalling frequency range of 0
33、.35 to 0.65.8.11 A data point at the origin, (0,0) should be included inthe data set.9. Presentation of Data and Calculations9.1 The data collected using this test method are to beplotted on a galling frequency versus applied stress diagram. Asample diagram depicting the results of three types of ma
34、terialsis shown in Fig. 5. The applied stress on the x-axis is found bydividing the applied force by the apparent area of contact, thatis, the cross-sectional area of the specimen. For the givenspecimen geometry, this area is 14.96 mm2. The gallingfrequency shown on the y-axis quantifies the percent
35、age ofspecimens that experienced galling at each applied load. Forexample, if 8 of the 12 specimens tested at a given loadexperienced galling, then the galling frequency for the associ-ated stress would be 8/12 or 0.667.9.2 Each of the load levels tested will result as a single datapoint on the gall
36、ing frequency versus stress diagram.9.3 A best fit curve can be fitted to the data once all of thedata points have been plotted on the diagram. This can beaccomplished by fitting a two parameter sigmoid equation tothe data. The two parameter sigmoid has the following form:f 511 1 e2Ss G50bD(1)where:
37、f = galling frequency,s = applied stress,G50= Galling50value, andb = related to the steepness of the curve.Parameters G50and b shall be fitted to the galling frequencyversus applied stress data. The best fit curve can also be drawnwith a French curve or similar drawing instrument in lieu ofmathemati
38、cally fitting the data to the sigmoid equation.9.4 The Galling50value, the stress at which 50% of thespecimens are expected to gall, can be determined using eitherthe parameters of the curve fit or the graphical results.9.4.1 The Galling50value is parameter G50in Eq 1.9.4.2 The Galling50value is det
39、ermined graphically byfinding the applied stress that corresponds to a point on thecurve where the galling frequency is 0.50. This galling fre-quency is shown with a bold line on Fig. 5.10. Report10.1 The following data should be included in the testreport:10.1.1 Material composition of specimens,10
40、.1.2 Hardness of specimens,10.1.3 Flatness of specimens10.1.4 Thermal history of specimens,10.1.5 Surface roughness, Ra, of contact surfaces prior totesting,10.1.6 Cleaning process used,10.1.7 Surface treatment history such as passivation, etc.,10.1.8 The Galling50value,10.1.9 Number of replicates p
41、erformed at each load,10.1.10 Magnitude of loading,10.1.11 Test system used, type, size, and10.1.12 Temperature, humidity, atmosphere.11. Precision and Bias11.1 Absolute magnitudes of galling resistance of materialcouples are not available because of the wide range variables inany given tribosystem
42、that influence galling resistance.FIG. 4 Photograph of Typical Specimens after TestingG19608411.2 No rigorous statement can be made regarding biassince there is no independent measure of galling resistance ofa given tribosystem.11.3 The wear measurement conditions established by thistest method are
43、designed to facilitate obtaining precise andreproducible data.11.4 The repeatability of the results using this test methodimprove with the number of replicates used to generate eachdata point and with the number of data points used to create thegalling frequency versus applied stress graph. Table 1
44、indicatesthe repeatability standard deviation and the coefficient ofvariation for various numbers of replicates and data points.11.5 The reproducibility standard deviation and coefficientof variation will be determined upon completion of an inter-laboratory testing program and will be available on o
45、r beforeJune 2011.12. Keywords12.1 adhesive wear; galling; galling resistance; macroscopicsurface damage; seized components; sliding metallic surfacesNOTESpecimens used in this sample test had a flatness of 0.002 mm, no heat treatment or surface treatment, and a surface roughness of 80 m. Thespecime
46、ns were cleaned using the process described in this test method. Twelve replicates were run at each load. The testing was performed in aservo-hydraulic universal testing machine. The hardness of the Type 303, 304, and 316 stainless steel specimens was 98, 107, and 102 Rockwell B,respectively.FIG. 5
47、Graphical Results of Three Different MaterialsTABLE 1 RepeatabilityANumber ofReplicatesper DataPointNumber ofDataPoints inData SetLevel of AppliedStress, MPaRepeatabilityStandardDeviation, s, MPaCoefficient ofVariation,CV, %12 4 2.0, 4.0, 6.0, 8.0 0.46 9.212 5 2.0, 4.0, 5.0, 6.0, 8.0 0.38 7.620 4 2.
48、0, 4.0, 6.0, 8.0 0.38 7.620 5 2.0, 4.0, 5.0, 6.0, 8.0 0.33 6.6AThe data in the table above is for a material couple with following parametersfor the sigmoid function shown in Eq 1: b = 1.2, and G50= 5.0.G196085ASTM International takes no position respecting the validity of any patent rights asserted
49、 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 any 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
