Page - 124 - in 3D Printing of Metals

Metals 2017,7, 64 Figure6.Alignedporesat successivesolidified layers for: (a)un-etchedand(b) etchedspecimenscut alongthex–zplane. Similar resultswereobservedforspecimens in they–zplane. Ontheotherhand,after the initial scanningofoneSLMsamplewhichhadarelativelycomplex geometry (Figure7a)byusingadvancedX-raycomputedtomography(XCT)undera lowresolution, asmall regionnear the innercircleprofileof thesamplewasfoundtohavethehighestporositycontent compared to other regions throughout the sample (Figure 7b). Throughdetailed scanningof this regionunderhighresolution, theporosity contentwas found tobe0.61%,withpore sizes ranging from5μmto~74μm,asshowninFigure8. Theporositycontent in thescannedregionwasalsonot evenlydistributed,with themajorityof theporesconcentratedclose to thesurface (innerwall)of the scannedregion(Figure9).However,acomparativestudyonporositycouldnotbecarriedoutbecause onlyonesamplewassubjectedto theXCTscan.Hence, theresultsobtainedwerenot representative forall316LSSsamples fabricatedbySLM. Figure7. (a)Three-dimensionalviewof theAM-fabricatedsamplewitharelativelycomplexgeometry; (b) 3Dviewof thesmall regionnear the innercircleprofile (redcircle in7a) furtherobservedunder highresolution. 124