µxct of Selective Laser Melted Components Process Optimisation, Characterisation & Control of Defects

Transcription

1 µxct f Selective Laser Melted Cmpnents Prcess Optimisatin, Characterisatin & Cntrl f Defects M.M. Attallah 1, J.P. White 1, W. Sun 2, P. Wlliams 2 1: Advanced Materials & Prcessing Lab. (AMPLab) 2: Natinal Physical Labratry (NPL)

2 AMPLab

3 Presentatin Outline Intrductin: Defect Frmatin in SLM. Aims & Objectives T characterise defects prduced by different laser parameters T have sme cntrl f the defects Experimental methd: Parts prduced using Selective Laser Melting in aluminium AlSi10Mg ally Scanned using uxct systems at NPL and UB Results Cnclusins

4 Defects ccur in SLM due t materials and prcess factrs. Intrductin Defect Frmatin in SLM Material factrs: Susceptibility t cracking: liquatin, slidificatin (ht tear), reheat, r ductility dip (weldability as a gd indicatr). Slubility f gases (e.g. Hydrgen in Al), gas pre frmatin. Pwder quality: inherent prsity in pwders, r surface xide film in Al-ally pwders.

5 Prcess factrs: Insufficient cnductin: lack f cnslidatin Evapratin/key hle Insufficient remelting Intrductin Defect Frmatin in SLM (Steen and Mazumder, 2010)

6 Aim & Objectives Aim: Highlight the utility f µxct in the characterisatin f the SLM prcess and materials inducted defects Objectives: 1) Characterise the defects prduced by different laser parameters: develpment f a single prcess ptimisatin artefact with multiple parametric cmbinatins. 2) Relate the 3D characterisatin methd t 2D ptical micrscpy techniques: influence f the 2D analysis planes/rientatin. 3) Prduce parts with cntrlled levels f defects: Final cmpnents and test artefacts. 4) Practical applicatins f µxct in SLM research.

7 ALM Technlgies (AMPLab) Selective Laser Melting/SLM (Pwder Bed) CONCEPT M2 CUSING system q Netshape fabricatin f cmpnents f Ni, Ti, NbSi, TiNi, Al, and steels. q Cmpnents have a density f >98+%. Laser system Fibre laser 400 W (cw) Build envelpe 250 x 250 x 280 mm Layer thickness µm Prductin speed 2 20 cm 3 /h Max. scanning speed 7 m/s Fcus diameter µm Semi-autmatic pwder recycle system

8 Develpment f a Multi-Parameter SLM Artefact

9 Cin Array Methd 37x 3mm cube sample array 1 Cin sample designed fr efficient Optical micrscpy analysis, part f a larger set 37 cubes each built with individual parameters Built using AlSi10Mg pwder, with LPW irregular mrphlgy pwder <63 µm Scanning strategy Cube Sample Supprt structure Cmpleted array structure Pwer (W) Scan Speed (mm/s) Hatch Spacing (µm) Increment Increment 45

10 Cin Array Methd µxct Wrk Scan: Perfrmed by NPL n Nikn µm vxel scan achieved Data prcessing: CT Pr fr recnstructin Vlume graphics fr slice utput Slice Analysis: Image J Renyi Entrpy threshlding XY, XZ & YZ plane utput Java macr fr scan subdivisin and area fractin measurement

11 Cin Array Methd Scan Overview Gd Range f samples prduced yielding single tracks, track calescence, and prsity/vids Track mrphlgy shws sme track wetting, but als sme angular scanning errrs Pres frm at track ends Pres frm near centre n lwer energy density samples Z X Z Y Y X

12 Cin Array Methd Scan Overview: Identificatin f Optimum Parameters 250 W Laser Pwer 60, 105, 150, 195, 240 µm hatch spacing 3500mm/s 4000mm/s 500mm/s 1000mm/s Scan speed 300 W Laser Pwer AMPLab mm/s 2000mm/s 2500mm/s Scan speed

13 Distance alng Z-axis (mm) Cin Array Methd High Hatch (300W, 2000 mm/s, 240 µm) XZ-plane: shws hatch gaps and track width alng X-axis YZ-Plane: shws near edge build up alng Y-axis XY-plane: shws verall area 40 fractin alng Z-axis Nte the planar differences XY Plane Distance alng x axis (mm) 4 YZ Plane, Parallel t Scanning Directin Density (%) Distance Alng Y axis (mm) Density (%) Density (%) XZ Plane, Nrmal t Scanning Directin

14 Cin Array Methd Medium Hatch (300W, 2000mm/s, 150 µm) XZ plane: shws hatch gaps are decreasing as tracks calesce alng X-axis. YZ-plane: Y axis shws edge and central build up. XY-plane: shws verall area fractin alng the Z-axis Density (%) XZ Plane, Nrmal t Scanning Directin Distance alng x axis (mm) Z axis height (mm) XY Plane Density (%) Density (%) YZ Plane, Parallel t Scanning Directin Distance Alng Y axis (mm)

15 Z axis height (mm) Cin Array Methd Lw Hatch (300 W, 2000 mm/s, 60 µm) XZ-plane: shws prsity prduced inside the melt pl alng X-axis (material-related). YZ-plane: shws prsity prduced at edges f cmpnent. XY-plane: axis shws verall area fractin variance. XY Plane Density (%) Density (%) Density (%) XZ Plane, Nrmal t Scanning Directin Distance alng x axis (mm) YZ Plane, Parallel t Scanning Directin Distance Alng Y axis (mm)

16 Cin Array Methd Discussin & Cnclusins Different planes can see different defects; Hatch-induced defects are best detected n the XY plane,. Meltpl defects are best detected in the XZ plane. Edge/build up defects and the YZ plane shws. The cin array methd reduces the effrt invlved in prcess ptimisatin and meltpl bservatins. Ideally, a cylindrical (vertical) array, with multi parametric cmbinatins, will give mre cnsistent X-ray paths.

17 Develpment f SLM Test Artefacts (Benchmarks)

18 SLM Test Artefacts Tailred defects 3: keyhle high energy density 2: regular vids hatch spacing is slightly insufficient 1: gd sme spatter induced vids 5: heat exchanger with sme pwder in the cavities. 4: Sinterin g Partially bnded particles

19 SLM Test Artefacts Prductin f Graded-Defects

20 SLM Test Artefacts Prductin f Equispaced Meshes Aim: t prduce a mesh with an equal track and gap width Different meshes frm um prduced Fine cntrl f laser parameters required t prduce equal track and gap size

21 Applicatins f µxct in SLM Investigatins

22 Research Highlights Selective Laser Melting f Lattice structures Aim: Investigate the influence f SLM parameters n the strut size, internal prsity and cmpressive strength f lattice structures. Apprach: Characterisatin f the size and internal prsity f lattices. Micrstructural and mechanical prperties characterisatin. (a)150w-3500mm/s, (b) 400W-3500mm/s, (c) 400W-1000mm/s C Qiu, S Yue, NJE Adkins, RM Ward, H Hassanin, PD Lee, PJ Withers, MM Attallah. Materials Science and Engineering A, 2015, vl. 628, pp

23 Influence f Pst-Prcessing using HIPping µxct Visualisatin f Crack Clsure in Ni-Superallys Island Scanning Strategy in SLM LN Carter, C Martin, PJ Withers, MM Attallah. Jurnal f Allys and Cmpunds, 2014, Vlume 615, pp

24 SEM Observatin f Crack Pattern In the As-fabricated cnditin it can be seen that the cracks when when bserved by SEM fall in the same 1mm x 1mm pattern.

25 HIP Treatment (Crack Cnslidatin) Small trial verified the HIP cnditin apprpriate T Slvus -T C; p MPa; x h This HIP cnditin appeared t wrk very successfully n the vertically built blcks Purely by gemetry and the directinality f the grain grwth, the hrizntally built bars appear t be susceptible t greater surface cnnectivity f cracks. Outer regin vulnerable t surface cnnected cracks (Apprx. 1mm-1.5mm wide) Build Directin

26 Influence f Pst-Prcessing using HIPping µxct Visualisatin f Crack Clsure in Ni-Superallys As-fabricated HIPped AMPLab 2015 LN Carter, C Martin, PJ Withers, MM Attallah. Jurnal f Allys and Cmpunds, 2014, Vlume 615, pp

27 Research Highlights Visualisatin f Defect Mrphlgy Large, multi layer near- Hrizntal vids can be seen due t pr wetting caused by xide films and lw melt penetratin. Smaller vids intersperse the main vids shwing a near randm rientatin, indicating these are melt pl (lack f fusin) defects. 1.7 µm vxel allws mrphlgy f 17 µm vids in each axis t be analysed.

28 Mnitring Drug Release in SLMed Implants Implants with Embedded Therapeutics (NIDMET) The use f ALM in the manufacture f drug-delivering metallic implants. Drugs will be fed int the implants during fixatin, and will be dispensed during their life t decrease the likelihd f infectin. SC Cx, H Hassanin, MM Attallah, DE Shepherd, O Addisn, U Gbureck, LM Grver. Materials Science & Engineering C: 2016.

29 Cnclusins & Future Wrk XCT is a pwerful tl t characterise SLM defects and track mrphlgy in 3D. The crrect analysis planes shuld be used t assess different defect levels (edge defects, melt pl, r hatching defects). Small vxel scans shw pres may span multiple layers and can cntribute t mechanical prperty anistrpy. Future wrk will be carried ut t lk int errr in the CT measurement n cmplex mesh gemetries.

30 Acknwledgements NPL: Peter Wlliams, Wenjuan Sun, Stephen Brwn Manufacturing Technlgy Centre (MTC) Dr. Mark Ward, UB Metallurgy & Materials UB science city labratry Students: Uriel Tradwsky

31 Fllw