Page - 42 - in 3D Printing of Metals

Metals 2016,6, 284 Figure 3. (a) Schematic of EBM-built Ti64 sampleswith thicknesses of 0.5, 1, 5, 10, and 20mm; (b)Schematicconfigurationof theball-on-discmicro-tribometer. 2.2. PowderAnalysis Morphological characteristicsof theTi64powderweredeterminedusingaMalvernMorphologi G3 S (Malvern Instruments Ltd., Worcestershire, UK). Powder samples of 5 mm3 in volume were dispersed on the glass plate. A 5× objectivewas used for themeasurement of this study. Fourparametersofparticle sizeviz.D10,D50,D90, andDaverage (sizebelowwhich10%,50%,90%,and averageparticle sizearepresent, respectively)werecalculatedfromtheparticle sizedistributioncurve. 2.3. SurfaceAnalysis Surfaceroughnessofas-builtandas-polishedTi64samples,andwornsurfaceswereexamined usingasurfaceprofilometer (Talyscan150) (TaylorHobsonInc.,RollingMeadows, IL,USA)witha diamondstylusof4μmindiameter.Chemical compositionsofas-built andas-polishedsurfaceswere analyzedwith theaidofX-rayphotoelectronspectroscopy(XPS;KratosAXISUltra,KratosAnalytical Ltd.,Manchester,UK).Both theas-built andtheas-polishedsampleswereslicedfromtheothersideof thesquaresandcut intopiecesof10mm×10mm×2mm.Allof theTi64sampleswereultrasonically cleaned inacetoneandethanol for30minrespectivelyandstored indryboxovernightbeforeanalysis wascarriedout. 2.4.MicrostructuralCharacterisationTechniques Microstructure,wearmorphologyandweardebriswere examinedusinga scanningelectron microscope(SEM;JEOL-JSM-5600LV;20kV, JEOLLtd.,Akishima, Japan).Chemicalcompositionof the weardebriswasexaminedbyenergy-dispersiveX-rayspectroscopy(EDX) (OxfordInstrumentsPlc., Abingdon,UK)equippedwithin theSEM. Inaddition,X-raydiffraction (XRD;PANalyticalEmpyrean; CuKα; 40mA;40mV;stepsizeof0.01◦) (PANalytical,Almelo,TheNetherlands)wasemployedfor phase identification. 2.5.MechanicalPropertiesEvaluation Vickersmicrohardness testswere carried out on the slightly-etched samples using aVickers micro-indentor (Future-techFM-300e) (FUTURE-TECHCorp.,Fujisaki, Japan)withanapplied load 42