简介:Sinceamorphousalloyshavewiderapplication,theycannotbefabricatedusingtheconventionalcoolingvelocity.ThebarmaterialplasmasprayingisadoptedtofabricateFebaseamorphousalloyinthisinvestigation.Thecrystallizationdegree,microstructure,micro-hardness,composition,crystallizationtemperatureoftheamorphousalloyandtheflyingrulesoftheatomizedparticlesintheprocessoftheplasmasprayaretested.Theresultsshowthatthealloypreparedhasthehighamorphousdegreeandhomogeneousmicrostructure,micro-hardnessandthecrystallizationtemperaturecanreach1187HVand531℃respectively.Theatomizationisverywellduringtheprocessofplasmaspraying;andthereishighthermalgradient,thecoolingvelocityreaches6.07×107K/s.
简介:Forthedevelopmentofalow-melting-pointfillermetalforbrazingaluminumalloys,aseriesofAl-Si-Cu-(Ni,Sn,Zn)fillermetalshavebeenstudied.Throughdifferentialthermalanalysis(DTA),themeltingtemperaturesofsuchAl-Si-Cu-(Ni,Sn,Zn)fillermetalsweredetermined.Theresultsshowthattheadditionof3wt.%-5wt.%SnintotheAl-6Si-15Cufillermetalcausesitssolidustemperaturetodecreasebyabout12℃.ThefillermetalwiththecompositionAl-6Si-l5Cu-2Niisproposed,whichpossessesameltingtemperaturerangeof512℃to520℃andamicrostructarethatincludesanAl-Cueutecticphases,Al-Si-Cueutecticphases,siliconparticlesandCu_2Al,AlNi_3,Al_7Cu_4NiandAl_3Ni_2intermetalliccompounds.Anadditionof5wt.%-7wt.%ZnintosuchAl-Si-Cufillermetalscausetheirsolidustemperaturestodropfurthertoavaluelowerthan498℃.MetallographicobservationsindicatethattheadditionofZnintotheAl-Si-CufillermetalinhibitstheformationoftheAl-Si,Al-CuandAl-Si-Cueutecticphases.TheremainingphasesareaAl_2Cuintermetalliecompound,anα-Alsolidsolutionandsiliconparticles.
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简介:ThefrictionandwearbehaviorofFe-Alintermetallicsbasedcoatingproducedbyhighvelocityarcsprayingtechniqueunderdryslidingatroomtemperaturewereinvestigatedusingaball-on-disctribotester.Theeffectofslidingspeedonfrictioncoefficientandwearofthecoatingwasstudied.Thewornsurfaceofthecoatingwasanalyzedbyscanningelectronmicroscope(SEM)toexploreslidingfrictionandwearmechanism.Theresultsshowthatthevariationsoffrictioncoefficientcanbedividedintothreedistinctstepsduringthetrail.Boththefrictioncoefficientandthewearofthecoatingincreasewithincreasedslidingspeedduetoacceleratedcrackpropagationrateandlamellarstructurewithpoorductilityofthecoating.Thecoatingsurfaceissubjectedtoalternatelytensilestressandcompressionstressduringslidingwearprocess,andthepredominantwearmechanismofthecoatingsappearstobebrittlefractureanddelamination.
简介:Dynamicsinpartialtransientliquidphasebonding(PTLPbonding)ofSi3N4ceramicwithTi/Cu/Timulti-interlayerwassystematicallystudiedthroughmicro-analysisofjointinterfaces.Theresultsshowthatgrowthofreactionlayerandisothermalsolidificationprocessiondoatthesametime.GrowthofreactionlayerandmovingofisothermalsolidificationinterfaceobeytheparaboliclawgovernedbythediffusionofparticipatingelementsduringthePTLPbonding.Coordinationoftheabovetwodynamicsprocessisdonethroughtimeandtemperature.Whenreactionlayerthicknessissuitableandisothermalsolidificationprocessisfinished,thehighbondingstrengthatroomtemperatureandhightemperatureareobtained.
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:我国是铝的第一生产大国,但是在上世纪80年代初,因铝导体生产工艺低下严重影响了铝导体的使用。主要制约铝导体推广和使用因素是达不到国际公认的61%IACS导电率水平,以及与导电率相矛盾的断裂强度与伸长率,这就严重地制约了铝导体的使用。随着科学技术的不断发展,铝导体加工工艺的不断进步,人们想出了可在铝的熔炼过程中加入一些其他元素,来弥补铝导体性能的不足,发展到今天就形成了铝合金导体。从2005年开始,铝合金导体在电缆中的使用逐步发展起来,由于铝合金导体除了在导电率上与铜存在差距,在导体压蠕变、柔韧性、抗腐蚀以及电缆敷设方面都优于铜导体电缆,同时,在导电率上也可以通过扩大导体截面来弥补载流量的缺陷,从而人们也慢慢开始使用铝合金材料作为电缆导体。
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: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.