Deposition Geometry Research Articles

TiB1.8 single layers and epitaxial TiB2-based superlattices by magnetron sputtering using a TiB (Ti:B = 1:1) target

Sputter-deposited titanium diborides are promising candidates for protective coatings in harsh and extreme conditions. However, growing these layers from TiB2 diboride targets by DC magnetron sputtering usually leads to over-stoichiometric layers with low crystal qualities. Moreover, superlattices with TiB2 as one of the constituents have been becoming popular, owing to their superior mechanical properties compared to single layer constituents in addition to their use in other applications such as neutron optics. Here, we propose the use of a TiB (Ti:B = 1:1) sputtering target in an on-axis deposition geometry and demonstrate the growth of epitaxial sub-stoichiometric TiB1.8 thin films. Furthermore, we present the growth of CrB1.7/TiB1.8 superlattices, from TiB (Ti:B = 1:1) and stoichiometric CrB2 targets, with abrupt interfaces as promising materials system for neutron interference mirrors. The high crystal quality structure with well-defined interfaces is the common feature of superlattices which, regardless of application, should be addressed during the growth process.Utilizing TiB target, all films crystallize in the hexagonal AlB2 structure. The sub-stoichiometry of the TiB1.8 films was accompanied by the presence of planar defects embedded in the films. CrB1.7/TiB1.8 superlattices exhibited a homogeneous boron distribution within the layers with no sign of B-rich tissue phases through the layers. This study demonstrates the feasibility for TiB as sputter target material, that offers a solution for deposition of TiB2-based superlattices without the need to adjust the deposition parameters. Such adjustments would otherwise be unavoidable for tuning the TiB2 composition and could affect the growth of the other constituent materials.

The influence of the nanostructure design on the corrosion behaviour of TiN thin films prepared by glancing angle deposition

This study reports on the influence of nanostructure design on the corrosion behaviour of titanium nitride (TiN) thin films, prepared by DC reactive magnetron sputtering, using the Glancing Angle Deposition (GLAD) technique. The primary objective was to explore how modifying the deposition geometry affects the growth design and surface features of TiN films (keeping roughly constant the N/Ti ratio) and compare these effects with those produced by changing the chemical composition within the same thin film system (N/Ti increasing ratios). For this, two groups of samples were prepared: Group 1 – the samples were prepared in the conventional geometry (normal growth) with varied nitrogen content (stoichiometric and non-stoichiometric films) and; Group 2 – the samples were prepared with modified growth geometries (inclined and zigzag, with increasing incidence angles), keeping an almost unchanged stoichiometry. The results revealed increased surface porosity and roughness for Group 2 films compared to Group 1, demonstrating that deposition geometry can affect more significantly the surface characteristics than the composition variations. Corrosion studies indicated that the films prepared within Group 2, despite having higher porosity, showed a more stable open circuit potential (OCP) and nobler values than the reference close-stoichiometric TiN0.92 film (reference sample) from Group 1. However, potentiodynamic polarization curves suggested higher corrosion kinetics for Group 2 films, most likely due to their increased surface heterogeneities. Electrochemical impedance spectroscopy (EIS) confirmed these findings, showing lower corrosion resistance for films prepared with inclined and zigzag geometries, if compared to the films prepared in conventional geometry (Group 1 samples).This study advances the current state of the art on this film's responses, by demonstrating that tailoring nanostructure design through deposition geometry offers a promising approach to optimize the corrosion behaviour of TiNx without the need to change its composition.

First step toward designing effective real-time control systems in laser directed energy deposition

In-process monitoring and control are essential for quality assurance and consistency of laser-based directed energy deposition processes. Detection of irregularities during deposition in terms of defects or flaws is based on in situ monitoring of output process parameters such as temperature, melt-pool geometry, or deposition height. The real-time feedback of these output parameters allows the development of control strategies for real-time adjustment of input process parameters, such as laser power or scanning speed, to correct detected deviations from the desired output process parameters. Therefore, criteria such as sensitivity, stability, correlation, trends, and interactions of the input-output process parameters have a direct impact on controller design, establishing, for example, control limits or tolerance ranges of the output parameters. This paper focuses on the study of the characteristics of output process parameters to input process parameters. This research involves analyzing and comparing the deposition of single tracks under various input process parameters, including laser power and scanning speed. Melt-pool geometry and temperature are estimated from a visual camera and a hyperspectral line camera, whereas the final deposition geometry is obtained from a laser triangulation scanner. The results show the linearity between input and output process parameters, the steadiness of the output process parameters, the relation between melt-pool and final deposition, and offer insights to design effective in-process control systems.

Computational modeling of multi-track multi-layer laser directed energy deposition process

This study presents the development of a 3D fully coupled thermomechanical finite element model to evaluate the melt pool geometry, defects, and micro-hardness of multi-track multi-layer deposition in the powder feed laser-directed energy deposition (LDED) technique. Fabrication strategies can significantly affect the melt pool geometry and material behavior of the manufactured components. Understanding the effect of process parameters in a multi-track multi-layer LDED is important. Optimal process parameters are crucial for achieving high-quality deposition in terms of deposition geometry and integrity. The model can aid in mitigating issues such as inadequate inter-track or track-substrate fusion, porosity, cracks, and other defects. A multi-track multi-layer finite element model (FEM) can realistically predict melt pool evolution, mechanical properties, and defects in laser-LDED. This work focuses on the development of a fully coupled thermomechanical model for multi-track multi-layer deposition processes using ABAQUS®. The finite element framework employs Johnson-Cook’s flow stress model for constitutive behavior and the Koistein-Marburger equation for predicting hardness. Two tracks and two layers of SS316L powder are deposited on an SS304 substrate in finite element simulations and experiments. The model has been validated for the melt-pool depth in the substrate, deposition geometry, heat-affected zone, and hardness. It has been observed that there is a ∼10 % error in the prediction of melt pool geometry characterization and a ∼12 % error in hardness as compared to experimental results. The melt-pool width, depth, substrate dilution, and hardness have been characterized as a function of process parameters via simulations and experiments. The model is capable of predicting inter-track and interface defects. In addition, the effect of interlayer cooling on the melt-pool geometry and hardness has been studied.

Evolution of Material Properties and Residual Stress with Increasing Number of Passes in Aluminium Structure Printed via Additive Friction Stir Deposition.

Additive friction stir deposition (AFSD) is an emerging solid-state additive manufacturing process with a high deposition rate. Being a non-fusion additive manufacturing (AM) process, it significantly eliminates problems related to melting such as cracking or high residual stresses. Therefore, it is possible to process reactive materials or high-strength alloys with high susceptibility to cracking. Although the residual stresses are lower in this process than with the other AM processes, depending on the deposition path, geometry, and boundary conditions, residual stresses may lead to undesired deformations and deteriorate the dimensional accuracy. Thermal cycling during layer deposition, which also depends on the geometry of the manufactured component, is expected to affect mechanical properties. To this day, the influence of the deposit geometry on the residual stresses and mechanical properties is not well understood, which presents a barrier for industry uptake of this process for large-scale part manufacturing. In this study, a stepped structure with 4, 7, and 10 passes manufactured via AFSD is used to investigate changes in microstructure, residual stress, and mechanical property as a function of the number of passes. The microstructure and defects are assessed using scanning electron microscopy and electron backscatter diffraction. Hardness maps for each step are created. The residual stress distributions at the centreline of each step are acquired via non-destructive neutron diffraction. The valuable insights presented here are essential for the successful utilisation of AFSD in industrial applications.

The Potential of Spot Size Control in Shaping the Thickness Distribution in Ultrashort Laser Deposition.

The availability of new-generation femtosecond lasers capable of delivering pulses with energies in the hundreds of mJ, or even in the joules range, has called for a revision of the effect of scaling spot size on the material distribution within the plasma plume. Employing a state-of-the-art Szatmári-type hybrid dye-excimer laser system emitting 248 nm pulses with a maximum energy of 20 mJ and duration of 600 fs, copper films were grown in the classical pulsed laser deposition geometry. The exceptionally clean temporal profile of the laser pulses yielded a femtosecond component of 4.18 ± 0.19 mJ, accompanied by a 0.22 ± 0.01 mJ ASE pedestal on the target surface. While varying the spot sizes, the plasma plume consistently exhibited an extremely forward-peaked distribution. Deposition rates, defined as peak thickness per number of pulses, ranged from 0.030 to 0.114 nm/pulse, with a gradual narrowing of the thickness distribution as the spot area increased from 0.085 to 1.01 mm2 while keeping the pulse energy constant. The material distribution on the silicon substrates was characterized using the f(Θ) = AcoskΘ + (1 - A)cospΘ formalism, revealing exponents characterizing the forward-peaked component of the thickness profile of the film material along the axes, ranging from k = 15 up to exceptionally high values exceeding 50, as the spot area increased. Consequently, spot size control and outstanding beam quality ensured that majority of the ablated material was confined to the central region of the plume, indicating the potential of PLD (pulsed laser deposition) for highly efficient localized deposition of exotic materials.

Thermal-structural Modeling of power electronic package: effects of deposition geometry and dry spot on the stress distributions

A Power Electronics package is a heterogeneous system made of semiconductor devices (dies), metallic-ceramic substrate, baseplate and encapsulating material.The electronic devices can be MOSFETs (Metal Oxide Semiconductors Field Effect Transistors), diodes, IGBTs (Insulated Gate Bipolar Transistors) and passive components such as capacitors, resistors and sensors integrated on support circuit; the complete set of semiconductor devices installed on a package form the so-called “power modulus”.These devices play an important role in the transmission and conversion of energy in electric and hybrid vehicles. Due to the elevated currents and, consequently, the elevated temperatures at which these systems work, and due to the mismatch of the thermal-mechanical properties of the materials from which they are made, stresses and strains develop within the devices.Such stresses can be locally concentrated and amplified, depending on the deposition geometry of the various layers constituting the semiconductor device. Edge termination structures are essential to decrease the electric field at die’s edges, and, including brittle compounds in their composition, like Si3N4 or SiO, they are quite sensitive to mechanical stress.Another reason that may cause the stresses concentrations is the presence of dry spots. Dry spots are areas of various size, located at the interface between die or leadframe and the encapsulating resin, where there is a total or partial lack of adhesion.The aims of this work are, mainly, two. At first, four linear finite element analyses have been performed in order to evaluate the stresses concentrations at the corners of edge termination structure.The first case concerns sharp corners and the other cases concern differently filleted corners. In the second part of this work, it has been analysed the dry spot effect on stress distributions. Due to the small size of the defect with respect to the whole package, a Global-Local FEM approach has been used, creating a local subdomain where the mesh is denser than the global domain and a running a further separate numerical analysis which takes its boundary conditions from the global analysis, so delivering reliable small-scale stress and strain gradients. This approach permits to achieve accurate analyses focused on zones of interest of the global domain, limiting the increase of the computational cost of the modelling.

Hybrid Analytical-Numerical Modeling of Surface Geometry Evolution and Deposition Integrity in a Multi-Track Laser-Directed Energy Deposition Process

Abstract Modeling multitrack laser-directed energy deposition (LDED) is different from single-track deposition. There is a temporal variation in the deposition geometry and integrity in a multitrack deposition, which is not well understood. This article employs an analytical model for power attenuation and powder catchment in the melt pool in conjunction with a robust fully coupled metallurgical-thermomechanical finite element (FE) model iteratively to simulate the multitrack deposition. The novel hybrid analytical–numerical approach incorporates the effect of preexisting tracks on melt pool formation, powder catchment, geometry evolution, dilution, residual stress, and defect generation. CPM 9V steel powder was deposited on the H13 tool steel substrate for validating the model. The deposition height is found to be a function of the track sequence but reaches a steady-state height after a finite number of tracks. The height variation determines the waviness of the deposited surface and, therefore, the effective layer height. The inter-track spacing (I) plays a vital role in steady-state height evolution. A larger value of I facilitates faster convergence to the steady-state height but increases the surface waviness. The FE model incorporates the effects of differential thermal contraction, volume dilation, and transformation-induced plasticity. It predicts the deposition geometry and integrity as a function of inter-track spacing and powder feed rate. The insufficient remelting of the substrate or the preceding track can induce defects. A method to predict and mitigate these defects has also been presented in this article.

Inherently Selective Atomic Layer Deposition for Optical and Sensor Applications: Microreactor Direct Atomic Layer Processing (μDALP™)

In parallel to additive manufacturing leading the revolution in traditional manufacturing, the same principles can revolutionize traditional thin film deposition techniques. Where lithography and vapor phase deposition techniques struggle, for example, with rapid iterations for prototyping or incompatibility with the used chemistry, additive manufacturing can shine. Indeed, several approaches are in development for 3D nanopriting1,2,3.Atomic Layer Deposition, and in more general Atomic Layer Processing, offers a unique opportunity for localized 3D processing/printing due to its two-step process. While simple in theory, due to well-developed examples of Spatial Atomic Layer Deposition (SALD), in practice miniturization of SALD requires substantial effort into the creation of suitable micro-nozzles. Uniquely, ATLANT 3D has developed proprietary Spatial ALD micronozzles, naming the process microreactor Direct Atomic Layer Processing - µDALPTM.The µDALPTM process undergoes the same cyclic ALD process but, thanks to the in-house microreactor development, is only done in a localized area. The microreactor or micronozzle confines the flows of gases used for ALD within a µm-scale area on the substrate, wherein the reactive species adsorb on the surface to deposit one monolayer of the desired material. Similarly, to spatial ALD, the creation of this monolayer then hinges on the movement of the substrate.4 Since the µDALPTM process is based on physical separation, it is theoretically compatible with any ALD process. As such, the material capabilities can match traditional ALD and exceed other special or patterning thin film techniques, such as lithography, which can be costly and time-consuming, especially for rapid prototyping required for innovation.Films deposited with ATLANT 3D technology have been shown to produce high-quality, crystalline, atomically precise thin films.1 It has been used to fabricate temperature (Fig.1) and capacitive sensors with sensitivities that meet or exceed those of devices made using conventional vapor phase deposition techniques.5 Low-cost rapid prototyping facilitated by ATLANT 3D technology of such devices enables design innovation and optimization not possible with other thin film deposition techniques.ATLANT 3D platform provides flexibility in deposition geometry (Fig.2) that enables a range of optical applications that require high-precision fabrication techniques. Optically transparent films can be used as localized thin protective layers for device encapsulation, as well as for atomic corrections of defects. Alternating deposition materials enable multilayer mirror fabrication of custom dimensions. Smooth thickness gradients can be used to manufacture ultrathin optical lenses. Overlapping depositions with discrete steps enable the manufacturing of binary lenses and phase masks. Growth rate enhancement in rastered direct processing mode using ATLANT 3D technology can produce periodic grating structures.1 Conformal coatings on complex surfaces can act as functionalization layers or seed layers for further material deposition through e.g. electrochemical processes.[1] Kundrata I. et al., ALD/ALE 2022 [Int. Conf.], 2022 [2] de la Huerta C. A. M. et al., arXiv, 2020, 0523. [3] Winkler, R. et al., J. Appl. Phys., 2019, 125, 210901[4] Paul Poodt., JVSTA., 2012, 30, 010802[5] Kundrata, I. et al., Small Methods., 2022, 6 (5), 2101546 Figure 1

Minimum cost, stability constrained preform optimization for hybrid manufacturing

This paper describes a new mathematical framework for optimum preform design in hybrid manufacturing, where additive manufacturing is combined with machining. The framework minimizes the combined cost for deposition and machining, while respecting the constraint imposed by machining stability (i.e., machining parameters that produce chatter are rejected). A case study is presented where a thin wall design is parameterized to describe the overbuilt deposition geometry. A grid of candidate solutions is selected to calculate cost and the stability limit considering both the part and tool dynamics. The minimum cost option is deposited and machined to demonstrate the approach.

Automated Interlayer Wall Height Compensation for Wire Based Directed Energy Deposition Additive Manufacturing.

Part quality monitoring and control in wire-based directed energy deposition additive manufacturing (w-DEDAM) processes has been garnering continuous interest from both the academic and industrial sectors. However, maintaining a consistent layer height and ensuring that the wall height aligns closely with the design, as depicted in computer-aided design (CAD) models, pose significant challenges. These challenges arise due to the uncertainties associated with the manufacturing process and the working environment, particularly with extended processing times. To achieve these goals in an industrial scenario, the deposition geometry must be measured with precision and efficiency throughout the part-building process. Moreover, it is essential to comprehend the changes in the interlayer deposition height based on various process parameters. This paper first examines the behaviour of interlayer deposition height when process parameters change within different wall regions, with a particular focus on the transition areas. In addition, this paper explores the potential of geometry monitoring information in implementing interlayer wall height compensation during w-DEDAM part-building. The in-process layer height was monitored using a coherent range-resolved interferometry (RRI) sensor, and the accuracy and efficiency of this measurement were carefully studied. Leveraging this information and understanding of deposition geometry, the control points of the process parameters were identified. Subsequently, appropriate and varied process parameters were applied to each wall region to gradually compensate for wall height. The wall height discrepancies were generally compensated for in two to three layers.

High-mass metal ion irradiation enables growth of high-entropy sublattice nitride thin films from elemental targets

Synthesis of high-entropy sublattice nitride (HESN) coatings by magnetron sputtering is typically done using custom-made alloyed targets with specific elemental compositions. This approach is expensive, requires long delivery times, and offers very limited flexibility to adjust the film composition. Here, we demonstrate a new method to grow HESN films, which relies on elemental targets arranged in the multicathode configuration with substrates rotating during deposition. TiVNbMoWN films are grown at a temperature of ∼520 °С using Ti, V, Nb, and Mo targets operating in the direct current magnetron sputtering mode, while the W target, operated by high power impulse magnetron sputtering (HiPIMS), provides a source of heavy ions. The energy of the metal ions EW+ is controlled in the range from 80 to 620 eV by varying the amplitude of the substrate bias pulses Vs, synchronized with the metal-ion-rich phase of HiPIMS pulses. We demonstrate that W+ irradiation provides dynamic recoil mixing of the film-forming components in the near-surface atomic layers. For EW+ ≥ 320 eV the multilayer formation phenomena, inherent for this deposition geometry, are suppressed and, hence, compositionally uniform HESN films are obtained, as confirmed by the microstructural and elemental analysis.

Recycling metal cutting chips into a consolidated deposition with friction surfacing

The objective of this research is to evaluate the feasibility of using metal cutting chips as a feedstock in solid-state metal additive manufacturing, with friction surfacing used as a demonstrator. To date, the recycling of metal cutting chips is an energy-intensive process. Compared to recycling processes that melt down metal chips, friction surfacing is a solid-state process, which should reduce the overall embodied energy needed to reuse the chips. While friction surfacing is primarily used for coating surfaces to improve their wear properties, it is also showing promising results as an additive manufacturing process for repair / remanufacturing features on large metal parts. Metal cutting chips of 316L stainless steel, produced by a milling operation, were pressed into hollow 304L stainless steel rods. The chip-filled rods were used as the [consumable] friction surfacing tools to deposit on 304L stainless steel substrates. The properties of the resultant deposits are analyzed and compared with deposits made by solid 304L and 316L tools, including deposition geometry, efficiency, process forces, and bond strength. Results indicate that a fully consolidated deposition can be created from the metal cutting chips using this process. Compared with a solid 304L tool, deposits made with metal chip-filled tools were narrower but thicker in the steady-state region when deposited with the same process parameters.

The influence of the nanostructure design on the optical, electrical and thermal properties of TiNx thin films prepared by reactive magnetron sputtering

This study investigated the impact of the nanostructure design of titanium nitride (TiNx) thin films on their optical, electrical and thermal properties. The growth designs of the films were tailored using conventional sputtering (series 1) and GLancing Angle Deposition (GLAD) geometries (series 2 and 3). The results showed the potential to modify the properties of thin films by adjusting their nanostructure design, rather than changing their composition. TiNx thin films prepared by GLAD, revealed wider and more significant variations in optical and electrical properties, while the thermal properties seemed to be more affected by the structural changes promoted by the N content in the films. GLAD geometries resulted in the reduction of the film's reflectivity, and colour coordinates, as well as an increase in the electrical resistivity. The thermal parameters of effusivity ratio and diffusivity were reduced as the N/Ti ratio increased.

Investigations on Deposition Geometry and Mechanical Properties of Wire Arc Additive Manufactured Inconel 625

Investigations on Deposition Geometry and Mechanical Properties of Wire Arc Additive Manufactured Inconel 625

A new efficiency calibration methodology for different atmospheric filter geometries by using coaxial Ge detectors

The study of the different pollutants present in atmospheric aerosols such as trace elements and radionuclides is essential to assess the air quality. To analyze the particulate matter (PM), atmospheric filters with different dimensions and geometries (rectangular, circular, slotted, and square filters) are usually employed. Regarding the pollutants existing in atmospheric aerosols, radionuclides are usually analyzed due to their multiple applications such as either in the environmental radiological control or as tracers of atmospheric processes. Therefore, this study aims to develop a new and general methodology to calibrate in efficiency coaxial Ge detectors to properly determine radionuclides present in the PM by gamma-ray spectrometry for several filter types. For this, granular certified reference materials (CRM) containing only natural radionuclides (238U-series, 232Th-series, and 40 K) were selected. Several granular solid CRMs were chosen allowing us to reproduce the same PM deposition geometry and to assure the homogeneity of the added CRMs. These are the main advantages in relation to the typical methods that use liquid CRMs. Furthermore, for filters whose surfaces are relatively large, they were cut in several pieces and placed one on top of the other, achieving the same geometry than the PM deposited onto the filter. Then, the experimental full-energy peak efficiencies (FEPEs) were obtained for each energy of interest (Eγ) and they were fitted versus Eγ, finding a general FEPE function for each filter type. Finally, this methodology was validated for both natural and artificial radionuclides (from 46 to 1332 keV) by using different filter types employed in proficiency test exercises, obtaining |zscore|< 2 for all cases.

Experimental investigations and parametric effects on depositions of super duplex stainless steel in wire arc additive manufacturing

Identification of suitable processing conditions is essential for successful fabrication of engineering components of any material by wire arc additive manufacturing (WAAM). Objectives of this article are to determine optimal process parameters for deposition of super duplex stainless steel (SDSS) ER2594 in gas metal arc welding (GMAW)-based WAAM using response surface methodology (RSM) and characterisation of the deposited materials. The developed RSM-based models of deposition geometry in terms of bead width and bead height, and deposition rate based on experimental data showed higher values of width, height and deposition rate for increasing voltage and wire feed speed due to higher heat input onto the tip of wire and decreasing torch travel speed and gas flow rate. Results of tensile tests of the deposited SDSS exhibited increase of mechanical properties like yield strength, ultimate tensile strength and elongation by 28.8%, 14.3% and 84%, respectively, compared to that of the cast SDSS material. Microstructural characterisations of the deposited SDSS wall using SEM exhibited a typically higher ratio of austenite to ferrite phases (77:23) with oriented columnar dendritic structure compared to that of the base material (50:50). Pre-heating of the substrate could enhance the deposited bead size with higher width due to higher energy available for melting and spreading of the beads.

Post-processing of additively manufactured IN625 thin-walled structures using laser remelting in directed energy deposition

Blown-powder directed energy deposition (DED) is especially useful for depositing on an existing part for the purpose of repair or adding features. Thin substrate deposition, wherein the width of the substrate is smaller than the laser diameter, is an important configuration for building and repairing complex components in various geometries. The present study seeks to understand the efficacy of in-line post-processing methods based on laser remelting (LR) for reducing internal (e.g., porosity) and external (e.g., surface roughness) for such thin-walled repair configurations. In this work, different levels of LR energy density and substrate width were evaluated using the LR process. Post processing outcomes in terms of deposit geometry as well as spatial distribution of porosity, pore density, pore volume fraction, pore diameter, and surface roughness were evaluated using X-ray microcomputed tomography and optical profilometry. The results showed that LR reduced pore density up to 88 % and reduced areal surface roughness to 4.159 μm. At some threshold, increasing LR energy density increased surface waviness and modified deposition geometry, this indicative of limits to the post processing method. Strategies for using LR to reduce total porosity, near-surface porosity, and improving surface roughness are briefly discussed.

Influence of normalized enthalpy on inconel 718 morphology in direct metal deposition

Morphology of each layer contributes to the final shape of a component fabricated by direct metal deposition process, because of the layer-on-layer fabrication technique. Hence, it's a requisite to understand the layer morphology evolution and factors affecting it. The present work deposited single tracks of Inconel 718 at systematically varied process conditions, and investigated their effect on the track/deposit geometry. The various parameters considered for the study are laser power ( P), scan speed ( v), and powder feed rate ( ṁ). The measurements carried on the deposits cross-section using optical microscope are width ( w), height ( h), and depth of penetration ( b). Additionally, dilution ( D %), deposit area, fusion zone shape and area are measured. The change in layer morphology with input parameters either individually or coupled, is also investigated. The coupled parameters are derived from the simultaneous variation of two are more individual parameters, such as linear heat input, line mass, and normalized enthalpy. The results have shown a proper relationship between input parameters and output morphology. Coupled parameters are observed to be a more valid measure in predicting the deposition geometry, than individual parameters. The relations obtained are linear between width and normalized enthalpy, height and line mass respectively. The fusion zone shape is evolving from semicircular to a wavy (double parabolic) nature with increasing energy input. The microstructure observations resulted a scenario of rapid cooling, and dendritic grain morphology.

On the application of the anisotropic enhanced thermal conductivity approach to thermal modelling of laser-based powder bed fusion processes

Computational simulation of the Powder Bed Fusion (PBF) process is a useful tool for predicting and analysing melt pool geometry during the deposition process. Advanced models that use Computational Fluid Dynamics (CFD) can accurately simulate the complex melt pool dynamics of the process but are typically computationally onerous to implement. CFD models require thermophysical data over a large temperature range that may be difficult to acquire for the material systems of interest. Heat conduction models, which are useful to industrial end users are easier to implement, but their accuracy can be compromised. The main difference between heat conduction and CFD modelling is the absence of convection (especially Marangoni convection). However, several sources in literature have highlighted a simple approach to mimicking the effects of Marangoni convection on the melt pool by artificially increasing the thermal conductivity of the liquid. However, due to its simplicity and lack of agreement within literature, the modified heat conduction approach is neither sufficiently robust nor universally consistent. Comparison to experimental data is lacking. In the present work, the heat conduction model is modified using an orthotropic description of anisotropic thermal conductivity in the liquid phase by applying directional correction factors. The correction factors are calibrated by comparing the predicted geometry against experimentally-obtained melt pool dimensions for single-layer, multiple tracks in Ti-6Al-4V processed by laser-PBF. After appropriate correction factors were selected, the modified heat conduction model gave results in good agreement with experiments. To test the general applicability of the approach, data from literature were analysed and simulated using the model. After correction factors were adjusted accordingly, the simulated results were validated over the range of power levels and scan speeds. • Transient thermal conduction model of the laser-based powder bed fusion process. • Melt pool geometry simulated using efficient modelling approach. • Track profile simulated with consolidated deposition geometry on the substrate. • Good agreement with bespoke experimental data and independent data from literature.