Designation:B390–92(Reapproved2006)StandardPracticeforEvaluatingApparentGrainSizeandDistributionofCementedTungstenCarbides1ThisstandardisissuedunderthefixeddesignationB390;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticeforthevisualcomparisonandclassifica-tionoftheapparentgrainsizeanddistributionofcementedtungstencarbidesislimitedtocementedtungstencarbidesthatcontainapproximately6,10,and18%cobalt.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2B657GuideforMetallographicIdentificationofMicro-structureinCementedCarbidesB665GuideforMetallographicSamplePreparationofCementedTungstenCarbides3.Terminology3.1DefinitionsofTermsSpecifictoThisStandard:3.1.1apparentgrainsize—theaveragediameterofatung-stencarbideparticleasmeasuredonanetchedmetallographi-callypolishedsurfaceofaspecimenofsinteredcementedcarbide.Theapparentgrainsizeisexpressedinmicrometresandisgenerallyreportedasarange.4.SignificanceandUse4.1Theapparentsizeanddistributionoftungstencarbidegrainsincementedcarbidesaffectsthematerial’swearresis-tanceandfracture.Foragivenchemicalcomposition,anincreaseintheaveragegrainsizewillresultinincreasedtoughnessanddecreasedwearresistance.Thispracticeillus-tratesrepresentativemicro-structuresforawiderangeoftungstencarbide-cobaltgrades.Thisisnotintendedtobeusedasaspecificationforcarbidegrades;producersandusersmayusethemicrographsandthegrainsizechartasaguideindevelopingtheirownspecifications.5.SpecimenPreparation5.1Specimensshallbepreparedformetallographicexami-nationinaccordancewithaproceduresuitableforthistypeofcementedca...
