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1、InfluenceofcyclictemperaturechangesonthemicrostructureofAISI4140afterlasersurfacehardeningT.Miokovića,V.Schulze,a,,O.VöhringeraandD.LöheaaInstituteofMaterialsScienceandEngineeringI,UniversityofKarlsruhe,76131Karlsruhe,GermanyReceived22February2006; revised14Jul
2、y2006; accepted22August2006. Availableonline15November2006.AbstractInrecentyearslasersurfacehardeningusingpulsedlasersourceshasbecomeanincreasinglyestablishedtechnologyinengineeringindustryandhasopenedupwiderpossibilitiesfortheapplicationofselectivesurfaceharde
3、ning.However,thechoiceoftheprocessparametersisgenerallybasedonexperienceratherthanontheirempiricalinfluenceontheresultingmicrostructure,andforhardeningprocesseswithcyclictemperaturechanges,almostnocorrelationsbetweenprocessparametersandhardeningresultsareknown.
4、Therefore,someproblemsregardingthechoiceoftheprocessparametersandtheirinfluenceontheresultingmicrostructurestillremain.Inparticular,thereisalackofdataconcerningtheeffectofcyclictemperaturechangesonhardening.Tofacilitateprocessoptimization,thispaperdealswithadet
5、ailedcharacterizationofthemicrostructurescreatedinquenchedandtemperedAISI4140(Germangrade42CrMo4)steelfollowingatemperature-dependentlasersurfacehardeningtreatment.Thestructurepropertieswereobtainedfrommicrohardnessmeasurements,scanningelectronmicroscopyinvesti
6、gationsandX-raydiffractionanalysisofretainedaustenite.Keywords:Austeniteformation;Martensitictransformation;Laserhardening;Cyclictemperaturechanges;MicrostructuralcharacterizationArticleOutline1.Introduction2.Experimental3.Microstructuralcharacterization3.1.Las
7、ersurfacehardeningwithsingleheatingandcooling3.2.Lasersurfacehardeningwithcyclictime–temperaturechanges4.Discussion5.SummaryAcknowledgementsReferences1.IntroductionDuringlasersurfacehardeningrapidthermalchangesareimposedonthematerial.Comparedwithconventionaltec
8、hniquesforselectivehardening,themainadvantageoflasersurfacehardeningistheintenseenergyfluxwhichpromotesextremelyhighheatingrates.Thisleadstocomplexchangesintheprocessedmater
