PlasmapasteboronidingtreatmentofthestainlesssteelAISI3041.IntroductionAA3003alloysinrecentyears,thedevelopmentofsurfacetreatmentprocesshasbeenextensiveresearchtoimprovetheapplicationofstainlesssteelunderhightemperatureandpressurewearandoxidationresistance.Stainlesssteelsurfacetreatmentmethodsavailable,includingnitrogen2,carburizing,plasmacoating,boronpenetrationInparticular,theborideisboronpenetrationanddiffusionintothesurfaceoftheboridelayer(hardness(HV)betweenin1300-2100)ofthesurfacetreatment.Boridelayerhasexcellentheatresistanceandcorrosionresistance,andboridehavebeenappliedtoimprovethevalve,burners,nozzlesandothersurfaceproperties,whentheyareexposedtohightemperatureandpressurewheninthewaterandoil.Recently,however,improvedtechnologysuchasplasmaBoronizinginfiltrationprocesshasbeenextensivelystudied,becausethetraditionalboronizingprocess,suchastheofficialsalt-bathandgasnitridingboron-boronwillappear,suchasenvironmentalpollution,toxic,explosivenatureoftheproblem.Plasmaboronizinghasmanyadvantagesovertraditionalboronizingprocess.Forexample,expectahighenergyefficiencyasasourceofhigh-energyplasmatobeusedinplasmaboronizingprocess,anddistortioncanbeminimized,becausetheprocessingtemperatureisrelativelylowerthanthetraditionalprocess.However,plasmaboronizingprocessalsohasitsownlimitations.BZH6andBC13gaswasusedasaboronsourcegas,butgasisrelativelyexpensiveandtoxic,explosive.Inavacuumchamberbyboronchloridecorrosionisanotherseriousproblemfortheplasmaboronizing.Inthisstudy,asthedevelopmentofasolutiontotheproblemmentionedaboveandmoreintheprocessofboronpenetrationinoneattempt,involvingtheuseofamorphousboronandborax(Na2B4O7)creamisasimpleprocessofplasmaPastyboronizingmethodshavebeendesigned,thebestplasmaboronizingpastehasconductedasurveyofprocessconditions,thustheformationofboridelayermethodhascertaincharacteristics2.ExperimentalTherealAISI304stainlesssteelspecimens(diameter15mm,thickness2.5mm)wasusedforthistest.Sandpaper(#1200),afterpolishingthesurfaceofthesamplespecimen,cleanoffthedirtafterthesamplesarebroughtintothelaboratory,intheH2atmosphereforsputtercleaningofthespecimenisthefirsttobecarriedout.InAr:H2(2:1)gasenvironment,withdifferentproportionsofboronandboraxmixtureofboronpenetrationagentsdoboronizingplasmatreatmentbegan,in1023,1073,1123,1173and1223Kseveralheatedatdifferenttemperaturesforupto7hours.Usingmicro-scanningelectronmicroscope(Hitachi5-2400)tostudyitsmicroscopicstructure,acceleratingvoltageof20kVelectronmicroprobeanalysisdone.Vickershardnesswasmeasuredusinga0.1kgforceload,usingtheaverageofsevenreadings.CuK-raydiffractionX-raydiffractionanalysiswasused.PlasmaPastyborideofapparatusanddetailsofothertrialsinreference6usingdescription.3.Resultsanddiscussion3.1CreammixtureratioofboridelayerformationFig1Theeffectofvariousratiosofamorphousboronandboraxmixturethicknessoftheboridelayer.Fig.1showstheproportionofpastewithdifferentborideinthe1123Ktemperatureinsulation1.5hoursaftertheboridelayerthickness.Observedwiththemassfractionof20%and70%ofboraxtoformathickboridelayer.Andwiththemassfractionof100%ofamorphousborontoformanymeasurablethicknessofboridelayerisnotobserved,whichmaybeattributedtothepenetrationofboroninplasmaduringtheamorphousboronasthemeltingpointduetosurfacediffusionofthelackofactivityofboron.Whenthemassfractionofboraxto20%,theactiveformoftheboridelayerwasobserved.Duringtheinfiltrationofboron,boronatoms,B0,iscreamoftheboronhydride(BnHm)ofdecomposition,andtheboronatomsintothemoltenboraxorB0glowdischargeintheactiveboronatomsB+1.Finally,theboronatoms,B+1,proliferation,andironreaction,andthentheformationofboridelayer.Withthemassfractionof30%and70%oftheboronpasteofboraxboridelayerformationwasalsoobserved,whichmaybeattributedtotheeffectivemechanismofliquidelectrolyte,whentheboraxwiththecreamintheincreaseinthenumber,themobilityofmoltenboraxincreasethetime.Moreover,themassfractionof40and55%ofthepaste,whentheslowrateofboridewasobserved,asshowninFigure1.Presumably,forincludinggas,electrolysis,electrolysis,etc.,avarietyofnon-liquidboronizingmechanism,theactiveingredientinthisrangewillbedifficultforsomereason,theneedforfurtherinvestigation.Figure1stainlesssteelboridelayerthicknesslessthanmildcarbonsteel,whichconfirmspreviouslyreportedresults7,8.Notonlybecauseofthestainlesssteelsurfacehasaprotectivelayer,butalsoinchrome,nickelborideonthesurfacebutalsotheprotectivelayer,theyformwiththegrainboundary,therebypreventingthediffusionofboron7,8.Itwasalsopointedoutthat,duetotheincreaseinthenumberofboron,pastebecomesexcessive,adhesiveonthesurfacewhentheplasmasamplesPastyboronizingbegan,leadingtotherecoveryofthiscreamisverylow.Consideringthehighcostofboron,thereforeinferplasmaPastyPastyboridecomponentswiththebestmassfractionof30%amorphousboronand70%ofborax.3.2EffectoftemperatureandtimeontherateofformationoftheboridelayerFig.2.RelationbetweentheboronidingtemperatureandtimesontheFigure2showsthetemperatureandtimeontheborideboridelayerdepth.Accordingtotheparabolictheory,withtheinfiltrationtimeandtemperatureincreasedboron,boridelayerdepthwillalsoincrease.Thisshowsthattheboridelayerformationratebecomesslowastimeincreasesboronpenetration.Thiscanbeexplainedbythefactthat:theformationofboridelayeronthesurfaceoftheNi-richlayerbelowandchromium-richlayerplaystheroleofdiffusionbarrier,inhibittheactivityofborondiffusion.Furtherexplanationwillbegivenlaterinthearticle.3.3Changesincross-sectionhardnessdistributionFig.3.HardnesscurvesofAISI304boronizedforvarioustimesat1173K.Plasmaboridespecimensin1023,1073,1123K,holdingsevenhourstogettheboridelayerthicknesscannotbemeasured,andtheirhardnessmeasurementisimpossible.In1173and1223Ktemperatureplasmaboronizing,i