Designation:B874−96(Reapproved2013)StandardSpecificationforChromiumDiffusionCoatingAppliedbyPackCementationProcess1ThisstandardisissuedunderthefixeddesignationB874;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisspecificationcoverstherequirementsforchromiumdiffusionofmetalsbythepackcementationmethod.Packdiffusionemploysthechemicalvapordepositionofametalwhichissubsequentlydiffusedintothesurfaceofasubstrateathightemperature.Thematerialtobecoated(substrate)isimmersedorsuspendedinapowdercontainingchromium(source),ahalidesalt(activator),andaninertdiluentsuchasalumina(filler).Whenthemixtureisheated,theactivatorreactstoproduceanatmosphereofchromiumhalideswhichtransferschromiumtothesubstrateforsubsequentdiffusion.Thechromium-richsurfaceenhancescorrosion,thermalstability,andwear-resistantproperties.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2B374TerminologyRelatingtoElectroplatingB487TestMethodforMeasurementofMetalandOxideCoatingThicknessbyMicroscopicalExaminationofCrossSectionB602TestMethodforAttributeSamplingofMetallicandInorganicCoatingsB697GuideforSelectionofSamplingPlansforInspectionofElectrodepositedMetallicandInorganicCoatingsB762TestMethodofVariablesSamplingofMetallicandInorganicCoatingsC664TestMethodsforThicknessofDiffusionCoatingD3951PracticeforCommercialPackagingE766PracticeforCalibratingtheMagnificationofaScan-ningElectronMicroscopeE1077TestMethodsforEstimatingtheDepthofDecarbur-izationofSteelSpecimensF1330GuideforMetallicAbrasiveBlastingtoDescaletheInteriorofPipe3.Terminology3.1Definitionsusedinthisspecific...
