简介:Inthisstudy,twokindsofWC–Cocoatingswithdifferentdecarburizationlevelsweredepositedbyhigh-velocityoxy-fuel(HVOF)sprayingusingtheultrafineWC–Cocompositepowderandcommercialmicronsizedpowder,respectively.Thehardnessandelasticmodulusweremeasuredonthetopsurfaceandcrosssectionsofthepreparedcoatingsbythenanoindentationmethod.Theresultsshowthattheultrafine-structuredcoatinghasmuchhigherdensityandinhibiteddecarburizationthantheconventionalcoating,whichthusresultsinhigherhardnessandelasticmodulusvaluesthanthemicronsizedcoating.Thewearresistanceofthermal-sprayedcermetcoatingsgreatlydependsonthecross-sectionalhardnessandelasticmoduluswhichreflectsthebondstrengthbetweensplatstosomeextent.Basedontheanalysis,abetterunderstandingofthemicrostructureandpropertiesincermetcoatingmaterialswasobtained.
简介:Thetungsten-inert-gas(TIG)arcweldingexperimentsofcementedcarbideYG30andsteel45werecarriedoutusingtheNi-Fe-Cfillingalloys.Theetaphasesandmechanicalpropertiesofweldedjointswereanalyzedbymeansofscanningelectronicmicroscope(SEM),transmissionelectronicmicroscope(TEM)coupledwithselecteddiffraction,electronicprobemicroanalysisandbendingstrengthmethods.Theexperimentalresultsshowthatthechemicalcompositionofthefillingalloysaffectsetaphaseformation.Whenthecarbonandnickelcontentsinfillingalloysare0.61wt%and55.29wt%,respectively,noetaphasesform.Andthejointbendingstrengthisthehighestto1.352GPa.Butiftheyare0.01wt%and55.38wt%,theetaphasesareformedattheboundariesofthecementedcarbideandtheweld,andthethicknessofetaphaselayerisabout110micrometers.Andthejointbendingstrengthislow.Usually,theseetaphasesareanomalouslygranular,andeasytoaccumulateattheboundariesbetweencementedcarbidesandtheweld.TheyaremultipleM6Crichintungstenandiron.
简介:研究了立方碳化物Cr3C2、VC以及稀土La添加剂对WC-Co合金中WC晶粒形貌以及合金硬度与韧性的影响。为了强化烧结过程中WC晶粒生长的驱动力,采用具有高烧结活性的纳米W和纳米C为原料。为了获得合金中WC晶粒的三维形貌,采用扫描电镜直接观察合金烧结体的自然表面。结果表明,合金添加剂对WC晶粒形貌及其粒度分布特征以及合金的硬度与韧性有较大影响。由于均质三角棱柱形板状WC晶粒的形成,WC-10Co-0.6Cr3C2-0.06La2O3合金具有极佳的硬度与韧性组合。讨论了合金中WC晶粒形貌的调控机制以及合金中WC晶粒形貌特征对合金性能的影响。
简介:采用扫描电镜、能谱仪以及X射线衍射仪对具有WC+β(β为钴基粘结相)两相结构的WC-11Co-0.71Cr3C2-0.06RE(RE为含La、Ce、Pr、Nd的混合稀土)硬质合金烧结体表面进行观察与分析。结果表明,在烧结过程中合金中的La、Ce、Pr、Nd通过定向迁移与烧结炉内气氛中的S、O等杂质元素结合,在合金烧结体表面形成RE2S3(主)和RE2O2S(少量)弥散相。从合金中Cr3C2的热力学稳定性、Cr在Co中的溶解度特性以及稀土原子激发等3个方面,对稀土迁移活性的激发机制和稀土原子的定向迁移机制进行分析与讨论。
简介:ESD(electrosparkdeposition)isapromisingprocesstoproducehardandwear-resistingcoatingsonmetallicsubstrates.InthispapermicrostructureandinterfacialcharacteristicsoftheWC92-Co8coatedontitaniumandcarbonsteelarepresented.Ametallurgicalbondingbetweenthecoatingandsubstrateisobtained.TheTielementwasfoundtodistributeinWC92-Co8atthemetalpool,aswellastheinterfacebydiffusion.SomenewphaseswereproducedinthecoatinglayerduetothechemicalreactionduringtheESDprocess.ExperimentalobservationandthermodynamicanalysiswereutilizedtostudythemechanismofESD.
简介:这份报纸在极其细小的颗粒的WC-12%Co合金的磁性、机械的性质上处理codopedVC/Cr3C2和sintering温度的效果。结果证明在最佳的比例的做的VC/Cr3C2的synergistic行动提高坚硬和合金的横向的破裂力量(TRS),与更多的同类的微观结构。当合金是在1430点的sintered时?C并且与0.5%Cr3C2/0.2%VC,TRS到达3786MPa,坚硬是91.7HRA和比0.6m小的谷物尺寸。谷物生长上的数字分析在sintering过程期间证明在WC谷物边界并且Cr3C2溶解在公司上猛抛的两VC分阶段执行减少固体/液体的界面的精力,溶解和降水的过程极大地被延迟,WC谷物变粗被禁止。
简介:采用超音速火焰(HVOF)喷涂制备了一种新型的由纳米、亚微米、微米WC颗粒和CoCr合金组成的多尺度WC-10Co4Cr金属陶瓷涂层,对比了双峰和纳米结构WC-10Co4Cr涂层,在分析了涂层组织的基础上,研究了多尺度涂层的孔隙率、显微硬度、开裂韧性和抗空蚀性能,并分析了多尺度WC-10Co4Cr涂层的空蚀行为和机理。结果表明,HVOF喷涂制备的多尺度WC-10Co4Cr涂层具有≤0.32%的孔隙率和高的开裂韧性,涂层中未发现明显的纳米WC脱碳现象。与双峰与纳米结构涂层相比,多尺度WC-10Co4Cr涂层表现出最优异的抗空蚀性能,在淡水中的抗空蚀性能分别比双峰涂层和纳米结构涂层提高了大约28%和34%。多尺度WC-10Co4Cr涂层的优异抗空蚀性能归结于其独特的微纳米结构和优良的性能,能有效阻碍空蚀裂纹的形成和扩展。
简介:Theexchangecouplingattheferromagnetic/antiferromagnetic(FM/AFM)interfaceisinfluencedbyboththemagneticstructureandthecrystallinemicro-structure.Co/FeMn/Cothinfilmswith0.4nmPtspacerlayerinsertedintotheCo/FeMnandFeMn/Cointerfacerespectivelyweredepositedbymeansofmagnetronsputtering.ThetwointerfacesuponandbeneaththeFeMnlayershowdistinctbehaviorsbeforeandafterthePtspacerinserted.ThereisaremarkableshrinkoftheinterfacialuncompensatedspinswithintheFeMnbottominterfacialmonolayers,whereasarelaxationofthepinningstrengthoftheFeMninterfacialspinsalongtheout-of-planedirectionoccursatthetopinterface.XRDanalysisindicatesthePtlayerupontheFeMnlayerformsanfcc(002)texture,implyingthemagneticdiscrepancybetweenthetopandbottomFeMninterfaceshascrystallinestructuralorigins.
简介:TheCurietemperatureof(Nd1-xPrx)2Fe14CoyBcompounds(x=0,0.2,…,1.0andy=O,2,4,6,14)hasbeendeterminedwithACinitialsusceptibilitymeasurement.ItwasfoundthatthevariationsofCurietempera-turewithxisnotlinearfory=0and14,whereasitislinearforothervaluesofy.Thelatticeconstantsof(Nd1-xPrx)2Fet14BweredeterminedbyusingX-raydiffraction.Thelatticeexpansionwasmostlyalongthecaxis,whereasthatalongthea-axisremainedpracticallyzeroforthewholeseries.ItissuggestedthatPratomsmayshowsitepreferenceinR2M14Bcompounds(M=FeorCo).DuetothesubstitutionofCoforFe.thetendencyofsitepreferenceofPrbecomeslesspronounced,whichmaybeattributedtothedecreaseofdiffer-enceofcrystalelectricfield(CEF)actingonthetworareearthsiteswiththeintroductionofCoorFe.Incon-trasttothatofthePratoms,thesitepreferenceofCoiu(Nd(1-x)Prx)2Fe(14-y)CoyBcompoundsdoesnotdependonthecompositionoftherareearthsublattice(R=NdorPr).
简介:Aseriesoftheelectrochemicalandlong-termcorrosiontestswascarriedoutina3.5wt%Na2SO4solutiononthermal-sprayedWC-17CoandWC-10Co-4Crcermetcoatingsinordertoexaminetheeffectofcompositionofbindermaterialsonthecorrosionbehavior.TheresultsrevealthattheoverallcorrosionresistanceoftheWC-17CocoatingisinferiortothatoftheWC–Co–CrcoatingsduetothecorrosionofbindermaterialswhichinduceWCparticlestofalloff.CoOandWO3oxidefilmsformonthesurfaceofWC-17CocoatinginNa2SO4solutionelectrochemicalcorrosionprocess,whichwillprotectthecoatingintheprocessofcorrosion.Cr2O3oxidefilmformedontheWC-10Co-4Crcoatingsurfacehasastronghinderedroletocorrosion.ThecorrosionmechanismofWC-17CocoatinginNa2SO4solutionisentirecorrosionofComatrix,whileitisfilm-holecorrosionmechanismforWC-10Co-4Crcoating.
简介:以MoO3粉、Mo粉、Si粉及Al粉为原料,采用机械合金化法合成了纳米Mo5Si3-20%Al2O3(质量分数)复合粉体。采用XRD、SEM、TEM和DTA等对复合粉体在球磨过程中结构变化进行了研究。结果表明:球磨10h后合成的Mo5Si3-20%Al2O3复合粉体,反应以爆炸模式进行。球磨30h后,Mo5Si3和Al2O3的晶粒尺寸分别为36.3nm和21.9nm。随着球磨时间的延长,Mo5Si3和Al2O3的晶粒尺寸变小,衍射峰宽化程度降低。DTA和XRD分析结果表明,复合粉体具有好的热稳定性,球磨30h后再在1000℃退火1h后复合粉体没有发生物相转变。更多还原
简介:Compositeplatingcontainingnanometer-sizedparticlesfromanon-aqueouselectrolyte;CompositeplatingofNi/SiCusingazo-cationicsurfactantsandwearresistanceofcoatings;Developmentofrapidcompositeplatingsystemformotorcycleenginecylinders;DynamicResponseofLaminatedCompositePlateusingFirstOrderShearDeformationTheory
简介:[篇名]Anewhybrid-enhanceddisplacement-basedelementfortheanalysisoflaminatedcompositeplates,[篇名]Atheoreticalandexperimentalinvestigationintomultilayeredpiezoelectriccompositetransducers,[篇名]AnalysisofacompositepiezoelectriccircularplatewithinitialstressesforMEMS,[篇名]AnalysisofStressandLoadTransferinanAdhesionBondBetweenCompositePlatesandConcrete,[篇名]Applicationoflaminationparametertorcliability-bascdoptimizationofsymmctriclaminatedcompositcplatc,[篇名]Bucklingbehaviorofagraphite/epoxycompositeplateunderparabolicvariationofaxialloads,[篇名]COMBINEDEFFECTSOFANISOTROPYANDHETEROGENEITYOFMATERIALSONULTRASONICFIELDRADIATION.
简介:Low-CoLa1.8Ti0.2MgNi8.9Co0.1alloyswerepreparedbymagneticlevitationmeltingfollowedbyannealingtreatment.TheeffectofannealingonthehydrogenstoragepropertiesofthealloyswasinvestigatedsystematicallybyX-raydiffraction(XRD),pressure-compositionisotherm(PCI),andelectrochemicalmeasurements.TheresultsshowthatallsamplescontainLaNi5andLaMg2Ni9phases.LaCo5phaseappearsat1,000℃.Theenthalpychangeofallhydridesiscloseto-30.6kJ·mol-1H2ofLaNi5compound.Annealingnotonlyincreaseshydrogencapacityandimprovescyclingstabilitybutalsodecreasesplateaupressureat800and900℃.Afterannealing,thecontractionofcellvolumeandtheincreaseofhydridestabilitycausethehighratedischargeabilitytoreduceslightly.Theoptimumalloyisfoundtobeoneannealedat900℃,withitshydrogencapacityreachingupto1.53wt%,anddischargecapacityremaining225.1mAh·g-1after140charge–dischargecycles.