Heat and fluid flow in additive manufacturing – Part II: Powder bed fusion of stainless steel, and titanium, nickel and aluminum base alloys

Abstract The most important metallurgical variables that affect the structure and properties of components produced by powder bed fusion (PBF) are examined using a model, proposed and validated in part-I of this paper. These variables include the temperature and velocity fields, build shape and size, cooling rates, solidification parameters, dendrite arm spacing, hardness, distortion and lack of fusion defects for four common alloys used in additive manufacturing (AM), stainless steel 316 (SS 316), Ti-6Al-4V, Inconel 718 and AlSi10Mg. The process parameters examined include laser power, scanning speed, powder layer thickness, packing efficiency and hatch spacing. Among the four alloys, the largest molten pool of AlSi10Mg ensures good fusional bonding among layers and hatches but exhibits high solidification shrinkage. Therefore, AlSi10Mg is the most susceptible to distortion among the four alloys. SS 316 exhibits the opposite trend because of its smallest molten pool among the four alloys. For a particular alloy, lack of fusion and distortion can be minimized by careful selection of hatch spacing and scanning speed. For the dendritic growth of SS 316 and AlSi10Mg, refinement of the solidification microstructure through close spacing of the dendrite arms can be achieved using thinner layers and faster scanning. Asymmetry in liquid pool geometry because of the difference in the thermal properties of powder bed and solidified build can be minimized by reducing the scanning speed.

[1]  Wei Zhang,et al.  Building digital twins of 3D printing machines , 2017 .

[2]  A. De,et al.  Spatial variation of melt pool geometry, peak temperature and solidification parameters during laser assisted additive manufacturing process , 2015 .

[3]  K. Mills.  Recommended Values of Thermophysical Properties for Selected Commercial Alloys , 2001 .

[4]  D. Gu,et al.  Tailoring surface quality through mass and momentum transfer modeling using a volume of fluid method in selective laser melting of TiC/AlSi10Mg powder , 2015 .

[5]  Jean-Pierre Kruth,et al.  Determination of geometrical factors in Layerwise Laser Melting using optical process monitoring , 2011 .

[6]  Mustafa Megahed,et al.  Metal additive-manufacturing process and residual stress modeling , 2016, Integrating Materials and Manufacturing Innovation.

[7]  Leilei Wang,et al.  A pathway to microstructural refinement through double pulsed gas metal arc welding , 2017 .

[8]  Radovan Kovacevic,et al.  The influence of heat accumulation on the surface roughness in powder-bed additive manufacturing , 2015 .

[9]  A. Foroozmehr,et al.  Finite Element Simulation of Selective Laser Melting process considering Optical Penetration Depth of laser in powder bed , 2016 .

[10]  J. S. Zuback,et al.  Building blocks for a digital twin of additive manufacturing , 2017 .

[11]  Amitava De,et al.  Dimensionless numbers in additive manufacturing , 2017 .

[12]  Bo Cheng,et al.  On Process Temperature in Powder-Bed Electron Beam Additive Manufacturing: Model Development and Validation , 2014 .

[13]  J. Schoenung,et al.  In-situ characterization of laser-powder interaction and cooling rates through high-speed imaging of powder bed fusion additive manufacturing , 2017 .

[14]  D. Mynors,et al.  A three-dimensional finite element analysis of the temperature field during laser melting of metal powders in additive layer manufacturing , 2009 .

[15]  Radovan Kovacevic,et al.  Numerical Modeling of Heat Distribution in the Electron Beam Melting® of Ti-6Al-4V , 2013 .

[16]  D. Gu,et al.  Influence of hatch spacing on heat and mass transfer, thermodynamics and laser processability during additive manufacturing of Inconel 718 alloy , 2016 .

[17]  Tarasankar DebRoy,et al.  Residual stresses and distortion in additively manufactured compositionally graded and dissimilar joints , 2018 .

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

[19]  J. Beuth,et al.  Rapid Solidification: Selective Laser Melting of AlSi10Mg , 2016, JOM.

[20]  T. Mukherjee,et al.  Printability of alloys for additive manufacturing , 2016, Scientific Reports.

[21]  Sainan Cao,et al.  Effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of TiC/Inconel 718 composites , 2016 .

[22]  Xu Han,et al.  Melt-pool motion, temperature variation and dendritic morphology of Inconel 718 during pulsed- and continuous-wave laser additive manufacturing: A comparative study , 2017 .

[23]  Carolin Körner,et al.  Defect generation and propagation mechanism during additive manufacturing by selective beam melting , 2014 .

[24]  Stan A David,et al.  Physical processes in fusion welding , 1995 .

[25]  Wei Zhang,et al.  Modeling of heat transfer, fluid flow and solidification microstructure of nickel-base superalloy fabricated by laser powder bed fusion , 2016 .

[26]  M. S. Wahab,et al.  Mechanical and Physical Properties of AlSi10Mg Processed through Selective Laser Melting , 2016 .

[27]  Alastair A. MacDowell,et al.  Damage evolution and failure mechanisms in additively manufactured stainless steel , 2016 .

[28]  Konda Gokuldoss Prashanth,et al.  Microstructure and mechanical properties of Al-12Si produced by selective laser melting: Effect of heat treatment , 2014 .

[29]  L. Ladani,et al.  Finite element simulation of laser additive melting and solidification of Inconel 718 with experimentally tested thermal properties , 2017 .

[30]  K. Zhou,et al.  Heat transfer and phase transition in the selective laser melting process , 2017 .

[31]  Amitava De,et al.  Mitigation of thermal distortion during additive manufacturing , 2017 .

[32]  C. Körner,et al.  Mesoscopic simulation of selective beam melting processes , 2011 .

[33]  Tarasankar DebRoy,et al.  An improved prediction of residual stresses and distortion in additive manufacturing , 2017 .

[34]  Carolin Körner,et al.  Fundamental consolidation mechanisms during selective beam melting of powders , 2013 .

[35]  S. Wang,et al.  Characterization of stainless steel parts by Laser Metal Deposition Shaping , 2014 .

[36]  A. Rubenchik,et al.  Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones , 2015, 1512.02593.

[37]  Yu-Che Wu,et al.  Parametric study of surface morphology for selective laser melting on Ti6Al4V powder bed with numerical and experimental methods , 2018 .

[38]  B. Stucker,et al.  Comparison of 3DSIM thermal modelling of selective laser melting using new dynamic meshing method to ANSYS , 2015 .

[39]  Zemin Wang,et al.  A comparison on metallurgical behaviors of 316L stainless steel by selective laser melting and laser cladding deposition , 2017 .

[40]  Amitava De,et al.  Heat transfer and material flow during laser assisted multi-layer additive manufacturing , 2014 .