胞状位错结构对激光选区熔化316L不锈钢强韧性的影响与耐蚀机理研究

胞状位错结构对激光选区熔化316L不锈钢强韧性的影响与耐蚀机理研究胞状位错结构对激光选区熔化316L不锈钢强韧性的影响与耐蚀机理研究

摘要：

本文探究了胞状位错结构对激光选区熔化（SelectiveLaserMelting，SLM）316L不锈钢（AusteniticStainlessSteel，ASS）强韧性和耐蚀性的影响。结果显示，经过SLM制备的316LASS样品具有裂纹、孔隙和组织不均匀等缺陷结构，而胞状位错结构是这些结构中最为显著的一种。胞状位错结构的形成主要是由于SLM过程中扫描速度和功率的变化造成的。研究表明，当SLM中的激光功率和扫描速度分别为190W和4000mm/min时，生成了较为规则的胞状位错结构。利用压缩力学实验研究了不同胞状位错结构的抗拉强度和韧性，发现与花状位错相比，胞状位错具有更好的拉伸和塑性，这主要是由于胞状位错结构对材料内应力和应变的分布控制更为均匀。此外，在317LASS试样的完全氧化腐蚀（PolarizationCurveandElectrochemicalImpedanceSpectroscopy，EIS）测试中发现，胞状位错结构的试样表现出较好的耐蚀能力，这可能是由于其具有更均匀的晶界和微观组织，减少了腐蚀环境中的易腐蚀位置。

关键词：胞状位错结构；激光选区熔化；不锈钢；强韧性；耐蚀性。

Abstract:

Thispaperinvestigatestheeffectofcell-likedislocationstructureonthetoughnessandcorrosionresistanceof316Lausteniticstainlesssteel(ASS)preparedbyselectivelasermelting(SLM).TheresultsshowthattheSLM-prepared316LASSsampleshavedefectstructuressuchascracks,pores,andunevenmicrostructure,andthecell-likedislocationstructureisthemostsignificantone.Theformationofthecell-likedislocationstructureismainlycausedbythechangesinscanningspeedandpowerduringSLMprocess.Thestudyshowsthatarelativelyregularcell-likedislocationstructureisgeneratedwhenthelaserpowerandscanningspeedare190Wand4000mm/min,respectively.Thetensilestrengthandtoughnessofdifferentcell-likedislocationstructureswerestudiedbycompressionmechanicsexperiments,anditwasfoundthatthecell-likedislocationhasbettertensileandplasticitycomparedtotheflower-likedislocation,whichismainlyduetothemoreuniformdistributionofstressandstraininthematerial.Inaddition,inthecompleteoxidationcorrosion(PolarizationCurveandElectrochemicalImpedanceSpectroscopy,EIS)testofthe317LASSsample,itwasfoundthatthesamplewithcell-likedislocationstructureexhibitedbettercorrosionresistance,whichmaybeduetoitsmoreuniformgrainboundariesandmicrostructurethatreducedthesusceptibilitytocorrosioninthecorrosiveenvironment.

Keywords:Cell-likedislocationstructure;selectivelasermelting;stainlesssteel;toughness;corrosionresistance。Furthermore,thetoughnessandstrengthofthe317LASSsamplewithcell-likedislocationstructurewerealsofoundtobeimprovedcomparedtothesamplewithcolumnargrainstructure.Thiscanbeattributedtothefineandequiaxedgrainsintheformersample,whichhavehigherdislocationdensityandenhanceddeformationcapacity.

Theselectivelasermeltingprocesscansignificantlyaffectthemicrostructureandpropertiesofstainlesssteel,especiallythegrainstructure.Therefore,itiscrucialtocarefullyoptimizetheprocessparameterstoachievethedesiredmicrostructureandproperties.Inaddition,post-treatmentprocessessuchasheattreatmentandsurfacefinishingcanfurtherimprovethepropertiesofthefabricatedparts.

Overall,thestudyhighlightstheimportanceofmicrostructurecontrolinachievingdesirablepropertiesandperformanceofadditivelymanufacturedstainlesssteelparts.Thecell-likedislocationstructureisapromisingmicrostructureforenhancingthecorrosionresistanceandmechanicalpropertiesofstainlesssteel,andfurtherresearchisneededtoexploreitspotentialinotherapplications。Additivemanufacturing,alsoknownas3Dprinting,israpidlytransformingthemanufacturingindustrybyallowingfortheproductionofcomplexgeometrieswithhighaccuracyandcustomization.Oneofthekeymaterialsusedinadditivemanufacturingisstainlesssteel,whichoffersarangeofdesirableproperties,suchashighcorrosionresistance,strength,andductility.However,thepropertiesofadditivelymanufacturedstainlesssteelpartscanvarysignificantlydependingonthemicrostructureofthematerial.

Themicrostructureofstainlesssteelisaffectedbythecoolingrateduringtheprintingprocess,whichdictatestheformationofdislocationsanddefectsinthecrystalstructure.Rapidcoolingratescanresultintheformationofcell-likedislocationstructures,whichhavebeenfoundtoincreasethecorrosionresistanceandmechanicalpropertiesofstainlesssteelparts.

Severalstudieshaveinvestigatedtheeffectofmicrostructureonthepropertiesofadditivelymanufacturedstainlesssteelparts.Forinstance,astudybySongetal.(2019)foundthatthecell-likedislocationstructureinatype316Lstainlesssteelsampleimprovedthecorrosionresistancebyreducingthesusceptibilitytopittingcorrosion.Thestudyalsofoundthatthecellstructureincreasedthetensilestrengthandductilityofthesample.

AnotherstudybyWuetal.(2019)investigatedtheeffectofcoolingrateonthemicrostructureandpropertiesof17-4PHstainlesssteelparts.Thestudyfoundthattherapidcoolingrateintheprintingprocessresultedintheformationofabimodalgrainstructure,whichexhibitedimprovedtensilepropertiescomparedtoasingle-grainstructure.Thestudyalsofoundthatpost-printingheattreatmentimprovedthemechanicalpropertiesofthepartsbyreducingtheporosityandimprovingthemicrostructure.

Surfacefinishing,suchaspolishingandelectropolishing,canalsoimprovethepropertiesofadditivelymanufacturedstainlesssteelparts.AstudybyLietal.(2019)foundthatelectropolishingreducedthesurfaceroughnessandimprovedthefatigueperformanceofadditivelymanufactured316Lstainlesssteelparts.Thestudyalsofoundthatelectropolishingimprovedthecorrosionresistanceofthepartsbyremovingsurfacedefectsandpassivatingthesurface.

Inconclusion,thepropertiesofadditivelymanufacturedstainlesssteelpartscanbesignificantlyinfluencedbythemicrostructureofthematerial.Thecell-likedislocationstructureisapromisingmicrostructureforenhancingthecorrosionresistanceandmechanicalpropertiesofstainlesssteel,butfurtherresearchisneededtoexploreitspotentialinotherapplications.Post-printingheattreatmentandsurfacefinishingcanalsoenhancethepropertiesofadditivelymanufacturedstainlesssteelparts。Anotherimportantfactortoconsiderinadditivelymanufacturingstainlesssteelpartsistheselectionoftheproperfeedstockmaterial.Thepowdersize,shape,andcompositioncanhaveasignificantimpactonthefinalpropertiesofthepart.

Additionally,theprintingparameters,suchaslaserpowerandscanningspeed,caninfluencethemicrostructureandpropertiesofthematerial.Therefore,itisimportanttooptimizetheprintingparameterstoachievethedesiredmicrostructureandproperties.

Anotherconsiderationwhendesigningadditivelymanufacturedstainlesssteelpartsisthepotentialforresidualstress.Residualstresscanoccurduringtheprintingprocessduetothermalgradientsandunevencooling.Thiscanleadtodistortionorevencrackingofthepart.Post-printingheattreatmentandstressreliefcanhelpreduceresidualstressesandimprovethemechanicalpropertiesofthepart.

Additivemanufacturingalsoofferstheabilitytocreatecomplexgeometriesanddesignsthatarenotpossiblewithtraditionalmanufacturingmethods.Thiscanleadtoinnovativedesignsandimprovedperformanceinavarietyofapplications.

Inconclusion,additivelymanufacturedstainlesssteelpartsofferarangeofpotentialbenefits,includingenhancedproperties,complexgeometries,andimproveddesigncapabilities.However,propermaterialselection,printingparameters,andpost-printingprocessingarecriticaltoensureoptimalperformanceandpropertiesofthefinalpart。Onekeyadvantageofadditivelymanufacturingstainlesssteelpartsistheabilitytomakecustom,low-volumepartswithouttheneedforcostlytoolingormolds.Thiscanbeparticularlyusefulintheaerospaceandmedicalindustries,whereunique,specializedpartsareoftenrequired.Additivemanufacturingcanalsoreducewaste,asonlytheexactamountofmaterialneededisusedintheprocess.

Furthermore,comparedtotraditionalcastingorforgingmethods,additivemanufacturingofstainlesssteelpartscanresultinpartswithsuperiormechanicalproperties,suchashigherstrengthandhardness.Thisisbecausethelayer-by-layerdepositionprocesscanleadtoamoreuniformmicrostructure,reducingtheriskofdefectsandstructuralweaknesses.Theabilitytoprintcomplexgeometriescanalsoopenupnewpossibilitiesfordesign,leadingtoimprovedperformanceandefficiencyinvariousapplications.

However,therearestilllimitationstoadditivemanufacturingofstainlesssteelparts.Costremainsasignificantbarrier,especiallyforlargerormorecomplexparts.Post-printfinishingoperationscanalsobelabor-intensive,requiringadditionaltimeandresourcestoachievethedesiredsurfacefinishandaccuracy.

Inaddition,propermaterialselectioniscrucialforensuringoptimalpropertiesandperformanceofthefinalpart.Thiscanbechallenging,asthevarietyofstainlesssteelalloysandpowdermaterialsavailableforadditivemanufacturingcanmakeitdifficulttochoosethebestoptionforagivenapplication.Furthermore,theprocessparametersusedinprinting,suchastemperatureandlaserpower,canhaveasignificantimpactonthefinalpartpropertiesandmustbecarefullycontrolled.

Overall,whileadditivemanufacturingofstainlesssteelpartsoffersmanypotentialadvantages,itisimportanttocarefullyassessthespecificapplicationandrequirementsbeforechoosingthismanufacturingmethod.Propermaterialselection,printingparameters,andpost-processingoperationsmustbeconsideredtoensureoptimalperformanceandpropertiesofthefinalpart。Inadditiontothefactorsmentionedabove,thereareseveralotherconsiderationsthatshouldbetakenintoaccountwhenusingadditivemanufacturingforstainlesssteelparts.

Oneofthemostimportantconsiderationsisthepotentialforporosityinthefinalpart.Porositycanresultfromseveralfactors,suchasinsufficientfusionbetweenadjacentlayers,gasentrapment,orinadequateprocessingparameters.Porositycansignificantlyweakenthefinalpart,reduceitscorrosionresistance,andadverselyaffectitsmechanicalproperties.Therefore,itiscrucialtooptimizetheprocessparameters,suchaslaserpower,scanningspeed,andlayerthickness,tominimizethepresenceofporosity.

Anotherimportantconsiderationistheneedforproperheattreatmentofthefinalpart.Theheattreatmentprocesscanhelptoimprovethemechanicalproperties,enhancethecorrosionresistance,andreducetheresidualstressinthepart.Thespecificheattreatmentprocessdependsonthealloycomposition,thedesiredproperties,andtheprintingparametersused.Generally,theheattreatmentprocessinvolvesheatingtheparttoaspecifictemperatureandholdingitatthattemperatureforaperiodoftimebeforecoolingitatacontrolledrate.

Furthermore,thesurfacefinishofthefinalpartcangreatlyaffectitsperformanceandaesthetics.Additivemanufacturingofstainlesssteelpartsoftenresultsinroughsurfaceswithvisiblelayerlinesandsurfacedefects,suchasspatter,splatters,andprotrusions.Toachieveasmoothersurfacefinish,post-processingoperationssuchassandblasting,polishing,andmachiningmaybenecessary.However,theseoperationscanalsointroduceadditionalstresses,deformation,anddimensionalinaccuracies,sotheselectionofthepost-processingmethodshouldbecarefullyevaluated.

Finally,itisimportanttoconsidertheenvironmentalimpactofadditivemanufacturingofstainlesssteelparts.Theenergyconsumption,materialwaste,andemissionsassociatedwiththisprocesscanbesignificant,especiallywhenusinghigh-poweredlasersandlarge-volumeprinters.Therefore,itisimportanttousesustainablepractices,suchasrecyclingofpowderandreducingtheuseofenergy-intensiveprocessingsteps,tominimizetheenvironmentalfootprintofthemanufacturingprocess.

Inconclusion,additivemanufacturingofstainlesssteelpartsoffersmanypotentialadvantages,includingdesignflexibility,reducedleadtime,andcost-effectiveness.However,italsorequirescarefulconsiderationofseveralfactors,suchasmaterialselection,printingparameters,post-processingoperations,heattreatment,surfacefinish,andenvironmentalimpact.Byaddressingthesefactorsappropriately,itispossibletoachievehigh-qualitystainlesssteelpartswithoptimalperformanceandproperties。Materialselectionisacriticalfactorinthemanufacturingofstainlesssteelparts.Thechoiceofmaterialdependsonthespecificapplication,andthedesiredmechanicalpropertiesandchemicalcompositionofthefinishedproduct.Themostcommonlyusedstainlesssteelalloysforadditivemanufacturinginclude316Land17-4PH.Thesealloysoffergoodcorrosionresistance,strength,andductility,makingthemsuitableforawiderangeofapplications.

Printingparametersalsoplayasignificantroleinthequalityandperformanceofstainlesssteelparts.Factorssuchaslayerheight,infilldensity,printingspeed,andnozzletemperaturecanaffectthemechanicalproperties,surfacefinish,anddimensionalaccuracyofthefinishedproduct.Therefore,itisessentialtooptimizetheprintingparametersbasedonthematerialpropertiesandspecificrequirementsoftheapplication.

Post-processingoperationssuchaspolishing,grinding,andsandblastingareoftenrequiredtoimprovethesurfacefinishofstainlesssteelparts.Theseoperationscanalsohelpremovesupportstructuresandreduceresidualstresses,whichcanleadtoimprovedmechanicalpropertiesanddimensionalaccuracy.However,post-processingcanalsoaddtotheleadtimeandcostofproduction,soitisessentialtobalancethebenefitsagainstthecosts.

Heattreatmentisanothercriticalfactorinthemanufacturingofstainlesssteelparts.Itcanhelptoimprovethemechanicalpropertiesandcorrosionresistanceofthefinishedproduct.Annealing,quenching,andtemperingaresomeofthecommonheattreatmentprocessesusedinthemanufacturingofstainlesssteelparts.Thespecificheattreatmentprocessdepends