A new method for assessing the recyclability of powders within Powder Bed Fusion process

Abstract Recycling metallic powders used in the additive manufacturing (AM) process is essential for reducing the process cost, manufacturing time, energy consumption, and metallic waste. In this paper, the focus is on pore formation in recycled powder particles of stainless steel 316L during the selective laser melting process. We have introduced the concept of optimizing the powder bed's printing area in order to see the extent of the affected powders during the 3D-printing process. X-ray Computed Tomography (XCT) is used to characterize the pores inside the particles. The results from image processing of the tomography (rendered in 3D format) indicate a broader pore size distribution and a higher pore density in recycled powders compared to their virgin counterparts. To elucidate on this, the Electron Dispersion spectroscopy (EDX) analysis and Synchrotron-based Hard X-ray Photoelectron Spectroscopy (HAXPES) were performed to reveal the chemical composition distribution across the pore area and bulk of the recycled powder particles. Higher concentrations of Fe, Cr, and Ni were recorded on the interior wall of the pore in recycled particles and higher Mn, S and Si concentrations were recorded in the outer layer around the pore area and on the surface of the recycled particle. The pore formation in recycled powder is attributed to out-diffusion of Mn, S and Si to the outer surface as a result of the incident laser heat during the AM process due to higher electron affinity of such metallic elements to oxygenation. HAXPES analysis shows a higher MnO concentration around the pore area which impedes the in-diffusion of other elements into the bulk and thereby helps to creates a void. The inside wall of the pore area (dendrites), has a higher concentration of Fe and Cr oxide. We believe the higher pore density in recycled powders is due, at least in part to composition redistribution, promoted by laser heat during the AM process. Nanoindentation analyses on both virgin and recycled powder particles shows a lower hardness and higher effective modulus in the recycled powder particles attributed to the higher porosity in recycled powders.

[1]  Ryan R. Dehoff,et al.  Recyclability Study on Inconel 718 and Ti-6Al-4V Powders for Use in Electron Beam Melting , 2016, Metallurgical and Materials Transactions B.

[2]  F. Calignano,et al.  A study of the microstructure and the mechanical properties of an AlSiNi alloy produced via selective laser melting , 2017 .

[3]  Josiah Cherian Chekotu,et al.  Advances in Selective Laser Melting of Nitinol Shape Memory Alloy Part Production , 2019, Materials.

[4]  R. Pelletier,et al.  High resolution pore size analysis in metallic powders by X-ray tomography , 2016 .

[5]  S. Babu,et al.  Localized Changes of Stainless Steel Powder Characteristics During Selective Laser Melting Additive Manufacturing , 2019, Metallurgical and Materials Transactions A.

[6]  Dermot Brabazon,et al.  Recyclability of stainless steel (316 L) powder within the additive manufacturing process , 2019 .

[7]  Brad Barnhart Characterization of Powder and the Effects of Powder Reuse in Selective Laser Melting , 2017 .

[8]  R. Hague,et al.  Quantification and characterisation of porosity in selectively laser melted Al–Si10–Mg using X-ray computed tomography , 2016 .

[9]  Ma Qian,et al.  Effect of Powder Reuse Times on Additive Manufacturing of Ti-6Al-4V by Selective Electron Beam Melting , 2015 .

[10]  Sonia Mariel Vrech,et al.  Advances in additive manufacturing for bone tissue engineering scaffolds. , 2019, Materials science & engineering. C, Materials for biological applications.

[11]  L. Murr A Metallographic Review of 3D Printing/Additive Manufacturing of Metal and Alloy Products and Components , 2018, Metallography, Microstructure, and Analysis.

[12]  M. Peltz,et al.  Characterization of Metal Powders Used for Additive Manufacturing , 2014, Journal of research of the National Institute of Standards and Technology.

[13]  W. Niu,et al.  Processing and properties of porous titanium using space holder technique , 2009 .

[14]  Julie M. Schoenung,et al.  Reuse of powder feedstock for directed energy deposition , 2018, Powder Technology.

[15]  Gunther Reinhart,et al.  Powder recycling in laser beam melting: strategies, consumption modeling and influence on resource efficiency , 2018, Prod. Eng..

[16]  Ana Paula Serro,et al.  Additive manufacturing of ceramics for dental applications: A review. , 2019, Dental materials : official publication of the Academy of Dental Materials.

[17]  C. Willson,et al.  Quantification of Grain, Pore, and Fluid Microstructure of Unsaturated Sand from X-Ray Computed Tomography Images , 2012 .

[18]  Jose Arturo Garza-Reyes,et al.  Exploring Industry 4.0 technologies to enable circular economy practices in a manufacturing context , 2019, Journal of Manufacturing Technology Management.

[19]  J. Rodelas,et al.  Evolution of 316L stainless steel feedstock due to laser powder bed fusion process , 2019, Additive Manufacturing.

[20]  G. Hughes,et al.  Hard x-ray photoelectron spectroscopy study of copper formation by metal salt inclusion in a polymer film , 2019, Journal of Physics D: Applied Physics.

[21]  J. S. Zuback,et al.  Additive manufacturing of metallic components – Process, structure and properties , 2018 .

[22]  Kurosh Darvish,et al.  Reducing lack of fusion during selective laser melting of CoCrMo alloy: Effect of laser power on geometrical features of tracks , 2016 .

[23]  Prahalada K. Rao,et al.  Layer-wise spatial modeling of porosity in additive manufacturing , 2018, IISE Trans..

[24]  Michael R. Hespos,et al.  Metallurgical and Mechanical Evaluation of 4340 Steel Produced by Direct Metal Laser Sintering , 2015 .

[25]  M. A. Donmez,et al.  Effects of powder recycling on stainless steel powder and built material properties in metal powder bed fusion processes , 2017 .

[26]  Prateek Saxena,et al.  Tooling for Production of the Green Fiber Bottle , 2018 .

[27]  A. Kimura,et al.  Reduction mechanism of surface oxide in aluminum alloy powders containing magnesium studied by x-ray photoelectron spectroscopy using synchrotron radiation , 1997 .

[28]  Julian R. Jones,et al.  Laser-matter interactions in additive manufacturing of stainless steel SS316L and 13-93 bioactive glass revealed by in situ X-ray imaging , 2018, Additive Manufacturing.

[29]  A. Shukla,et al.  The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range. , 2018, Journal of synchrotron radiation.

[30]  Brian A. Hann,et al.  Powder Reuse and Its Effects on Laser Based Powder Fusion Additive Manufactured Alloy 718 , 2016 .

[31]  M. Yakout,et al.  On the characterization of stainless steel 316L parts produced by selective laser melting , 2018 .

[32]  Michael F Toney,et al.  Dynamics of pore formation during laser powder bed fusion additive manufacturing , 2019, Nature Communications.

[33]  A. Clare,et al.  Spatter and oxide formation in laser powder bed fusion of Inconel 718 , 2018, Additive Manufacturing.

[34]  S. Biamino,et al.  An investigation on the effect of powder recycling on the microstructure and mechanical properties of AISI 316L produced by Directed Energy Deposition , 2019, Materials Science and Engineering: A.

[35]  Ken Gall,et al.  The effect of surface topography and porosity on the tensile fatigue of 3D printed Ti-6Al-4V fabricated by selective laser melting. , 2019, Materials science & engineering. C, Materials for biological applications.

[36]  R. Hague,et al.  A Study on the Laser Spatter and the Oxidation Reactions During Selective Laser Melting of 316L Stainless Steel, Al-Si10-Mg, and Ti-6Al-4V , 2015, Metallurgical and Materials Transactions A.