简介:Widegapbrazing(WGB)experimentsusingthebuttedspecimenwitha1.5mmgapwerecarriedoutfortherepairofthefailedK418Bsuperalloylow-pressureturbinevanes.Thehightemperaturecreeprupturestrengthsofthebrazedjointsweretested,andthemicrostructuresandfracturesurfacesofthejointswereobserved.TheresultsshowthatthemicrostructureofK418Balloyjointiscomposedofdenseequiaxedgrain,smallanddiscretecompoundswithafewmicro-pores.Duringthecreeprupturetest,thecracksinitiatepreferentiallyatthemicro-poreorthegrainboundary,thenpropagatealongthegrainboundarytillthefracturehappens.Thecreeprupturestrengthat700℃ofthebrazedjointswith50%brazemetalintheworkingpartcouldexceed90%thatoftheK418Bsuperalloy,andthejointswith100%brazemetalintheworkingpartachieve70%to80%ofthecreeprupturestrengthsfortheK418Bbasemetal.
简介:Anewtechnology,thetwo-steptransientliquidphasediffusionbonding(TLP-DB)technologyforcobalt-basedK640superalloy,wasinvestigated.Themethodconsistsofashort-timehightemperatureheatingtomeltinterlayerfollowedbyisothermalsolidificationofliquidphaseatalowertemperaturethanthatoftheconventionalTLP-DB.Theresultindicatesthatthetwo-stepTLP-DBcanreliablyproduceanidealjointwithuniformchemicalcomposition,whichissuperiortothejointweldedbyconventionalTLP-DBinmicrostructureandmechanicalproperties.Bondingparametersofnewprocessare1250℃for0.5hand1180℃for3h.Thehigh-temperaturetensilestrengthofthejointbytwo-stepTLP-DBreaches74%ofthatofthebasematerialonanequalbasis,butthehigh-temperaturetensilestrengthofthejointbyconventionalTLP-DBisonly58%ofthatofthebasematerial.
简介:Inthispaper,thebrazingmechanismofLY12aluminumalloyatmiddlerangetemperaturewaspresented.TheCsF-AlF3non-corrosivefluxwasutilizedtoremovethecomplexoxidefilmonthesurfaceofLY12aluminumalloy.TheresultsrevealedthattheoxidefilmwasremovedbytheimprovedCsF-AlF3fluxaccompaniedwiththeoccurrenceofreactionaswellasdissolutionandthecompoundsCsFplayedanimportantroletoremovetheoxidefilm.Actually,thehighactivityofflux,say,theabilitytoremovetheoxidefilm,wasduetothepresenceofthecompounds,suchasNH4F,NH4AlF4andcompositemoltensalt.TheproductionofHFwasthekeyissuetoacceleratethereactionandenhancetoeliminatetheoxidefilmbydissolution.ItwasfoundthattherareearthelementLaatsmallpercentagewasnotenrichedattheinterface.Moreover,therareearthfluorideenhancedthedissolutionbehavior.
简介:Ni-basedsuperalloyK465isbrazedwithBNi-2fillermetalbyvacuumelectronbeambrazing(VEBB).InprocessofVEBB,effectsofprocessingprimaryparametersonshearstrengthofjointsareinvestigated.MicrostructureofthebrazedjointwithBNi-2fillermetalisstudiedbymeansofscanningelectronmicroscopy(SEM),energydispersivespectroscopy(EDS)andX-raydiffraction(XRD).TheresultsshowthatthestructureofbrazedseamconsistsofalargeamountofNi-basedγsolidsolution,Ni3Al(γ′),Ni3B,WB,CrB,andasmallquantityofWC,NbC.Themaximumshearstrengthofthejointis398MPawhenthebeamcurrentofweldingis2.6mA,heatingtimeis480sandfocusedcurrentis1800mA.
简介:ThevacuuminductionbrazingofSiCparticulatereinforcedLY12alloymatrixcompositeusingAl-28Cu-5Si-2Mgfillermetalhasbeencarriedout.Themicrographofthejointinterfacewasobservedbyscanningelectronmicroscopy.Thejointstrengthwasdeterminedbysheartests.Theresultsshowthatbrazingtemperature,holdingtime,SiCparticlevolumepercentageandpostheattreatmentinfluencejointstrength.SiCparticleshappeninthebrazingseamandthedistributionofSiCparticlesinthejointisnotuniform.Particle-poorzonesinthejointexistnearthebasemetal,andparticleconcentratezonesexistinthecenterofthebrazingseam.Inaddition,thefailureofthecompositeispredominantlyinitiatedbytherootingofSiCparticleinthebrazingseamandthemicro-crackexpandedalongthebrazingseamwithlowenergy.
简介:Inthispaperanewmethodforpreventingweldinghotcracking—theinversestrainmethod(ISM)isdevelopedontheprincipleofweldingmechan-ics.EffectivenessandfeasiblityofmethodinpreventingweldinghotcrackingofhighstrengthaluminumalloyLY12CZbysynchronousrollingduringwelding(SRDW)alongbothsidesoftheweldatasuitabledistancebehindtheweldingarcareexamined.ExperimentalresulteindicatethatweldinghotcrackingofLY12CYcanbeeffectivelypreventedandthemechanicalpropertiesofweldedjointcanalsobeimprovedbythemethod.Itisanimportantnewsolutionforpreventinghotcrackinginweldingofsheetmetal.
简介:Themechanicalproperties,creepdamage,creeprupturestrengthandfeaturesofinterfacialfailuresofweldedjointsbetweenmartensite(SA213T91)andpearlitesteel(12Cr1MoV)havebeeninvestigatedbymeansofargontungstenpulsedarcwelding,hightemperatureacceleratedsimulation,creeprupture,mechanicalpropertytestsandscanningelectronicmicroscope(SEM).Theresearchresultsindicatethatthemechanicalpropertiesofovermatchedandmediummatchedjointdeteriorateobviously,andtheyaresusceptibletocreepdamageandfailureafteracceleratedsimulationoperation500h,intheconditionofpreheat250℃,andpostweldingheattreatment750℃×1h.However,themechanicalpropertiesofundermatchedjointarethebest,theinterfacialfailuretendencyofundermatchedweldedjointislessthanthoseofmediumandovermatchedweldedjoint.Therefore,itisreasonablethatlowalloymaterialTR31isusedasthefillermetalofweldbetweenSA213T91and12Cr1MoVsteel.