ASTM_G_196_-_08_2016.pdf

Designation:G19608(Reapproved 2016)Standard Test Method forGalling Resistance of Material Couples1This standard is issued under the fixed designation G196;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 parentheses 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,nonmetallic 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 conditions 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 standard 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 Definitions used in this test method given in Terminol-ogy G40.3.2 Definitions:3.2.1 apparent area of contactarea of contact between twosolid surfaces defined by the boundaries of their macroscopicinterface.3.2.2 gallingform of surface 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.3.2.3 triboelementone of two or more solid bodies thatcomprise a sliding,rolling,or abrasive contact,or a bodysubjected to impingement or cavitation.(Each triboelementcontains 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-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 available 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 criterion 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.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 has been shown to have higherrepeatability than Test Method G98 in determining the gallingresistance.Test Method G98 can be used for initial ranking ofgalling resistance.1This 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.1,2016.Published November 2016.Originallyapproved in 2008.Last previous edition approved in 2008 as G196 08.DOI:10.1520/G0196-08R16.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 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.Thegalling 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 continues to operate satisfactorily andloses dimension gradually,then galling is not present,and thewear should be evaluated by a different te