简介：

简介：

简介：

简介：

简介：Sinceamorphousalloyshavewiderapplication,theycannotbefabricatedusingtheconventionalcoolingvelocity.ThebarmaterialplasmasprayingisadoptedtofabricateFebaseamorphousalloyinthisinvestigation.Thecrystallizationdegree,microstructure,micro-hardness,composition,crystallizationtemperatureoftheamorphousalloyandtheflyingrulesoftheatomizedparticlesintheprocessoftheplasmasprayaretested.Theresultsshowthatthealloypreparedhasthehighamorphousdegreeandhomogeneousmicrostructure,micro-hardnessandthecrystallizationtemperaturecanreach1187HVand531℃respectively.Theatomizationisverywellduringtheprocessofplasmaspraying;andthereishighthermalgradient,thecoolingvelocityreaches6.07×107K/s.

简介：TheenergymodelwasfoundedtocalculatethecriticalpowerofkeyholeformationbyusingthelimitprincipleinCW(continuouswave)Nd:YAGlaserdeeppenetrationweldingprocess.Themodelwasvalidatedbyexperiments.Theresultsshowthattherearetwoerrorsbetweenthecalculatedcriticalpowerofkeyholeformationandthatofexperiments:oneisthatthecalculatedresultsislessthanthoseofexperiments,whichiscausedbynotconsideringtheenergylossby!heatconductioninthemodelofkeyholeformation.Theotheristhatthereis0/9mmerrorbetweentheaxisofthecalculatedcurveofcriticalpowerwithlocationoflaserfocusandthatofexperimentalcurve,whichisinducedbytheexcursionoflaserfocusinlaserdeeppenetrationwelding.Atlast,thetwoerrorswererevisedaccordingtotheanalysesoftheerrors.

简介：

简介：

简介：ThefrictionandwearbehaviorofFe-Alintermetallicsbasedcoatingproducedbyhighvelocityarcsprayingtechniqueunderdryslidingatroomtemperaturewereinvestigatedusingaball-on-disctribotester.Theeffectofslidingspeedonfrictioncoefficientandwearofthecoatingwasstudied.Thewornsurfaceofthecoatingwasanalyzedbyscanningelectronmicroscope(SEM)toexploreslidingfrictionandwearmechanism.Theresultsshowthatthevariationsoffrictioncoefficientcanbedividedintothreedistinctstepsduringthetrail.Boththefrictioncoefficientandthewearofthecoatingincreasewithincreasedslidingspeedduetoacceleratedcrackpropagationrateandlamellarstructurewithpoorductilityofthecoating.Thecoatingsurfaceissubjectedtoalternatelytensilestressandcompressionstressduringslidingwearprocess,andthepredominantwearmechanismofthecoatingsappearstobebrittlefractureanddelamination.

简介：AnexperimentalsetupofacquiringthecoaxialvisualimageofthemoltenpoolandkeyholeinhighpowerNd:YAGlaserweldingisintroducedinthispaper.Itisoneofthemostdifficultproblemsinacquiringcoaxialimagethatthecoaxialimagingsignalofmoltenpoolandkeyholemustbeseparatedfromthelaserbeamwithhighpower.Thisproblemwasresolvedbydesigningadichroiticspectroscope.Thecharacteristicsofimagingsignalwereanalyzedandthecoaxialimageofmoltenpoolandkeyholewasacquired.Asmoothingfilterandahomomorphicfilterweredesignedtoremovethelowfrequencynoiseandtoenhancetheimageaccordingtothecharacteristicsofimagingsignal.Atlast,edgesofmoltenpoolandkeyholeweredetectedandextractedbasedonimagesegmentationwiththreshold.

简介：

简介：Inordertosolvethehigh-priceandshort-lifetimeproblemsofthecutterofagriculturalmachinery,andimprovethewearresistanceofthecutter,theTiCN/FemetalceramiccompositecoatingwaspreparedonthesubstrateofQ235steelbyreactionnitrogenarccladdingtechnique.ThemixturepowderoftitaniumandgraphitewaspreplacedontheQ235steelsurfaceafterintensivemixingbyplanetaryballmillandgluingwithstarchbinder.Themicrostructureandphaseofthecoatings,interfacebehaviorbetweencoatingsandthesubstratewereinvestigatedbyscanningelectronicmicroscopeandX-raydiffractometer.Themicro-hardnessdistributionofthecoatingsectionwastestedbymicro-hardnesstester.Frictioncoefficientandwearweightlossweremeasuredbyabrasionmachine.Wearingsurfacemorphologywasinvestigatedbyscanningelectronicmicroscope.TheresultsshowthatanexcellentbondingbetweenthecoatingsandtheQ235steelsubstrateisensuredbythestrongmetallurgicalinterfaceandphaseofthecoatings.ThecoatingsaremainlycomposedofTiCN.Thehighestmicrohardnessofthecoatingsreaches1089HVO.2,whilethemicro-hardnessofQ235steelsubstrateisonlyabout286HVO.2.Theanti-abrasivetestresultsshowthatthewearresistanceofthecladdingcoatingisbetterthanthatofquenchedandtempered65Mnsteelwhichisoftenusedascutterofagriculturalmachinery.ThefieldtestresultsshowthattheTiCN/Femetalceramiccompositecoatingpreparedbyreactionnitrogenarccladdingisfeasibletothemanufactureandremanufactureofthecutterofagriculturalmachinery.

简介：Anewhardfacingprocess,reactivebrazecoatingprocess(RBCC)wasstudied,and(TiC+Cr3C2)/FecompositecoatingswerepreparedbyRBCCusingcarbon,Cr3C2,iron,ferrochromiumandtitaniumpowderastherawmaterialsinvacuumbrazefurnace.TheresultsshowthatTiCisin-situsynthesizedinthecoatings.ThemethodsofintroducingCr3C2havegreateffectsonthedistributionofTiC.AddingCr3C2directlytotherawmaterialsforcoatings,fineTiCparticlesaggregateintodiscoidsparalleltothecoatingsurface,whereas,in-situsynthesizingCr3C2incoatings,theaggregationsofTiCarelumpish.Duringbrazecoating,Cr3C2particlesdirectlyaddeddissolveandprecipitatetobecomeneedle-shaped.Thecoatingshaveanevenandsmoothsurfaceandarecombinedwiththeirmildsteelsubstratesbyametallurgicalbonding.

简介：本试验利用CMT-TWIN双丝焊接技术,在Q235基体上堆焊Φ1.2ER5356和Φ1.2ER50S-6,以获得致密、无裂纹孔洞等缺陷的Fe-Al堆焊层。堆焊层主要由柱状晶组成,内部析出了细小的弥散相,EDS表明堆焊层存在Fe3Al。硬度测试表明：熔合区硬度分布不均匀,硬度峰值达450HV,而焊缝中心区硬度大致在350-400HV之间,表明此区域可能含Fe3Al较多。

简介：EffectsofalloyelementsonthemicrostructureandcrackresistanceofFe-C-Crweldsurfacinglayerwereinvestigated.Theresultsshowthatmicrostructuresofthelayermainlyconsistofcarbidesandaustenitematrix.IncreasingCandCrcontentsimpairthecrackresistanceofthelayerduetoincreasedamountofbrittlecarbides.TheadditionofNi,NborMoimprovesthecrackresistanceofFe-C-CrweldsurfacinglayerbyincreasingtheamountofausteniteandformingfineNbCorM7C3carbidesinthelayer.But,theexcessiveNb(>2.50wt%)orMo(>1.88wt%)impairsthecrackresistanceofthelayer,whichhasrelationwithincreasedcarbidesorcarbidecoarseningandaustenitematrixsolidsolutionstrengthening.ThepropercombinationofC,Cr,Ni,NbandMocanfurtherimprovenotonlythecrackresistanceofFe-C-CrweldsurfacinglayerbutalsotheerosionresistanceasaresultoffineNbCandM7C3carbidesdistributinguniformlyinaustenitematrix.Theoptimallayercompositionsare3.05wt%C,20.58wt%Cr,1.75wt%Ni,2.00wt%Nband1.88wt%Mo.

简介：

简介：

简介：

简介：Fe3AlandCr18-Ni8steelwerebondedinvacuumandaninterfacewasformedbetweenFe3AlandCr18-Ni8steel.Stressdistributionatthediffusion-bondedinterfacewasresearchedbynumericalsimulationandfiniteelementmethod(FEM).TheresultsindicatedthatthepeakstressappearedattheinterfacenearCr18-Ni8steelside.Thisisthekeyfactortoinducecrackatthisposition.Withtheenhancementofheatingtemperature,thepeakstressatthebondedinterfaceincreases.Whenthetemperatureis1100℃,thepeakstressisupto65.9MPa,whichisbiggerthanthatat1000℃by9.4%.Inaddition,thepeakstressbecomesbiggerwiththeincreaseofthethicknessofbasemetalfrom1mmto8mm.Whilethethicknessismorethan8mm,thepeakstressvariesslightlywiththechangeofthethickness.

简介：Comparisonsofparticle'sthermalbehaviorbetweenFe-basealloyandboroncarbideinplasmatransferred-arc(PTA)spacewasmadebasedontheoreticalevaluationresultsinthisarticle.ItwasfoundthatmostoftheFebaseparticleswouldbefullymeltedwhiletheytransportingthroughthecentralplasmafieldwith200Asurfacingcurrents.Andtheparticleswithadiameterlessthan0.5×10-4mmightbefullyevaporated.However,fortheboroncarbide(B4C)particles,onlytheonewithadiameterlessthan0.5×10-4mcouldbemeltedinthesamePTAspace.MostofB4CparticlesareonlypreheatedatitssolidstatewhentheywerefedthroughthecentralfieldofPTAplasmawhenthesurfacingcurrentisequaltoorlessthan200A.Whenthearccurrentwassmallerthan100A,onlytheparticlessmallerthan0.5×10-4mcouldbemeltedinthePTAspacefortheFe-basealloy.AlmostnoneofthediscussedB4Cparticlescouldbemeltedinthe100APTAspace.