Powder Feed Research Articles

Introduction of the Experimental Setup for the Investigation of the Novel Selective Melt Dispersion (SMD): A Directed Energy Deposition (DED) Process

This study focuses on developing an experimental setup to investigate the Selective Melt Dispersion (SMD), a Directed Energy Deposition (DED) process. SMD as a means of in-process joining (IPJ) aims to integrate components and assemblies during additive manufacturing, combining the advantages of various processes for eco-friendly and economical resource utilization. The research initially analyzed DED systems and defined requirements for subsystems and the overall system. Critical subsystems, including the energy source, material feed, and others, were sequentially developed, and a proof of concept involved building 20 stacked welded tracks, validated through micrograph analysis. The study concludes by evaluating and discussing the fulfillment of the defined requirements. The system comprises a centrally arranged vibration-assisted powder feed; a laterally arranged laser incidence at a 45° angle; a kinematic structure where all axes are arranged on the workpiece, so the powder supply does not require movement; and a shield gas supply.

Comparison of microstructure, mechanical, and electrochemical performance of laser-deposited FeCrV15 alloy at varying powder feed rates

In the realm of surface modification, repair, and reinforcement of components exposed to challenging operational conditions, such as tillage tools, laser cladding stands out as an innovative manufacturing technique. Employing this additive manufacturing approach, a functionally graded material with outstanding strength and properties is incorporated to enhance the desired attributes of the base material. This comparative investigation scrutinized and assessed the microstructural characteristics, hardness, wear resistance, and corrosion behavior of high carbon ferrochrome FeCrV15 coatings fabricated at two distinct powder feed rates, namely 5 and 6 g/min, respectively. The analysis delved into how the resultant coatings' molten bead deposition, microstructural evolution, hardness, wear resistance, and corrosion resistance were influenced by the powder feed rate. Evaluation of hardness was conducted using a Vickers microhardness testing apparatus, while phase identification was accomplished utilizing an X-ray diffractometer. The morphologies of the microstructures were scrutinized employing optical microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Furthermore, the corrosion response of the deposits in a soil–water environment was probed utilizing an Autolab potentiostat. A comprehensive assessment of the coatings' sliding wear performance was undertaken using an Anton Paar Tribometer. The findings of the study reveal that an escalation in the powder feed rate engenders heightened grain refinement within the microstructure, yielding a defect-free sample and augmenting the wear performance (with a wear rate of 2.42 × 10–6 mm3/N/m for sample B, surpassing 2.39 × 10–5 mm3/N/m for sample A and outstripping 1.72 × 10–3 mm3/N/m for the steel substrate). Additionally, the corrosion resistance is enhanced (with a corrosion rate of 0.0032 mm/yr for sample B, surpassing 0.0036 mm/yr for sample A, which, in turn, exceeds 0.1168 mm/yr for the steel substrate) in the case of sample B.

Process Parameter Optimization of Directed Energy Deposited QT17‐4+ Steel

AbstractThe feasibility of using argon‐atomized QT 17‐4+ stainless steel powder for directed energy deposition (DED) additive manufacturing is studied. The QT 17‐4+ steel is a novel martensitic steel designed based on the compositional modification of the standard 17‐4 precipitation‐hardened (PH) stainless steel. This modification aims to achieve better mechanical properties of as‐deposited components compared to the heat‐treated wrought 17‐4PH steel. In this study, QT 17‐4+ steel powder is used for DED, for the first time. The influence of laser power, laser scan speed, powder feed rate, and hatch overlap on the density is studied. The central composite design is used to determine the experimental matrix of these factors. The response surface methodology is used to obtain the empirical statistical prediction model. Both columnar and equiaxed parent austenite grain structures are observed. X‐ray diffraction analyses reveal a decrease in the percentage of retained austenite from 19% in the powder to 5% after DED. The microhardness of the DED processed sample in the as‐deposited state is slightly higher than that of wrought 17‐4PH steel either solution‐annealed or H900‐aged. A higher 0.2% yield strength, a lower ultimate tensile strength, and lower elongation are observed for the vertically printed test sample, when compared to the horizontal one.

Regulation on microstructure and mechanical properties of SiC particles reinforced AZ31 magnesium matrix composites fabricated by synchronous feeding of powder and wire in wire-arc directed energy deposition

Ceramic particles reinforced magnesium matrix composites (CMMCs) have attracted widespread attention and investigation due to their excellent comprehensive performances. However, limited research on additive manufacturing of CMMCs has been performed. In this work, the SiC/AZ31 composites were fabricated by wire-arc directed energy deposition (WA-DED) based on the synchronous feeding strategy of powder and wire. The defects, SiC particle distribution, microstructure and mechanical properties of the prepared WA-DED SiC/AZ31 composites were studied. The results indicated that SiC particles with the content range of 0.3–1.7 wt% have been successfully added into the single-channel monolayer AZ31 matrix by adjusting the turret speed (TS) and the argon gas flow rate (AGFR) flowing through the powder feeder. The mathematical model is established to predict the introduced SiC particle content by correlating the relationship between SiC particle content and process parameters (TS and AGFR) of the powder feeder. The transformation from columnar to equiaxed grains occurs after adding SiC particles, more precipitated phases are formed after introducing more SiC particles. Compared to the AZ31 matrix, the WA-DED SiC/AZ31 composites exhibit the highest yield strength of 92.8 MPa and tensile strength of 213.3 MPa on the premise of almost no loss of elongation, and the maximum improvement efficiency of tensile strength reaches 56%, which is mainly ascribed to refinement strengthening, while thermal mismatch strengthening, Orowan strengthening and load-bearing strengthening play a booster action.

Effect of B4C content and particle sizes on the laser cladded B4C/Inconel 625 composite coatings: Process, microstructure and corrosion property

B4C/Inconel 625 composite coatings were successfully prepared on 20 pipeline steel by laser cladding, in which B4C ceramic was selected as reinforcement phase to improve the microstructure and corrosion property of Inconel 625 coating. The laser cladding parameters were optimized and the effect of B4C content and B4C particle sizes on the microstructure and properties of B4C/Inconel 625 composite coatings were studied in detail. With increasing liner energy density and decreasing powder feeding speed, the crack ratio of the composite coatings reduces. NiB phase forms due to the in-situ reaction of B4C with Ni element in Inconel 625, and a thin layer of planar crystal also forms at the coating/substrate interface. As the addition of B4C content ranged 5 wt.%∼10 wt.% and the particle sizes ranged 10 μm–60 μm, the quantities of equiaxed crystals increase obviously and the coarse columnar crystals are also refined, which contributes to the improved microhardness and corrosion resistance of the B4C/Inconel 625 composite coatings. When the B4C content is 10 wt.% and particle size is 10 μm, the maximum microhardness of the composite coating is about 567HV0.2, which is 241.2% to that of Inconel 625 coating. The optimal corrosion resistance of B4C/Inconel 625 composite coatings is obtained when the B4C content is 5 wt.% and particle size is 60 μm.

Study on shallow configuration preparation and macroscopic and microscopic properties of cemented carbide surface

This study aimed to reduce surface configuration defects and improve the service performance of the configuration surface. The configuration was prepared using the principle of preset powder feeding laser cladding. Macroscopic and microscopic properties of the shallow configuration were tested to understand the mechanism behind the preset cladding material's ability to repair defects and improve surface hardness, and the preparation process of the shallow configuration was obtained. Finally, the method's potential for improving the wear resistance of the configuration surface was evaluated through friction and wear tests. The results indicate that the flow of molten preset powder can fill in pores, leading to the formation of a dense cladding layer on the configuration surface. This process also minimizes the generation of defects and holes. The incorporation of hard phases, such as TiN, Ti2N, and the solid solution (Ti, W)C1-X, positively influences the improvement of surface hardness and wear resistance of shallow configuration. When the average laser energy density ranges from 70 to 120 W·cm−2, the average microhardness of the shallow configuration surface is elevated by 13.4% compared to that of the conventional configuration surface. The friction force on the shallow configuration surface is 13.1% lower than that on the conventional configuration surface when the laser power is set to 80%, the scanning speed is maintained at 1500 mm/s, the scanning passes are 9, the spacing between configurations is 130 μm, and the configuration diameter is 50 μm. This technique presents a novel approach to producing configuration surfaces with enhanced quality.

Microstructural Evolution, Hardness and Wear Resistance of WC-Co-Ni Composite Coatings Fabricated by Laser Cladding.

This study investigated how process parameters of laser cladding affect the microstructure and mechanical properties of WC-12Co composite coating for use as a protective layer of continuous caster rolls. WC-Co powders, WC-Ni powders, and Ni-Cr alloy powder with various wear resistance characteristics were evaluated in order to determine their applicability for use as cladding materials for continuous caster roll coating. The cladding process was conducted with various parameters, including laser powers, cladding speeds, and powder feeding rates, then the phases, microstructure, and micro-hardness of the cladding layer were analyzed in each specimen. Results indicate that, to increase the hardness of the cladding layer in WC-Co composite coating, the dilution of the cladding layer by dissolution of Fe from the substrate should be minimized, and the formation of the Fe-Co alloy phase should be prevented. The mechanical properties and wear resistance of each powder with the same process parameters were compared and analyzed. The microstructure and mechanical properties of the laser cladding layer depend not only on the process parameters, but also on the powder characteristics, such as WC particle size and the type of binder material. Additionally, depending on the degree of thermal decomposition of WC particles and evolution of W distribution within the cladding layer, the hardness of each powder can differ significantly, and the wear mechanism can change.

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.

Influence of processing parameters on the thermal history, microstructure and tensile properties of Inconel 738 produced by laser directed energy deposition

In this paper, laser directed energy deposition (LDED) technology was applied to produce non-weldable Inconel 738 parts. The influence of processing parameters including laser power, scanning speed and powder feeding rate on the thermal history of molten pool and the morphology of single track was evaluated. Considering the surface quality and deposition efficiency, the appropriate processing parameters for multilayer deposition were selected. Then the impact of laser power on the microstructure evolution and tensile properties of IN738 thin-wall parts was investigated. The research results show that increasing the laser power could increase the peak temperature and molten pool lifetime, but decrease the cooling rate. Increasing the scanning speed significantly increased the cooling rate but had little effect on the peak temperature. The thermal history was hardly affected by the powder feeding rate, but a too high powder feeding rate caused the particle adhesion and decline of surface quality. The microstructure of LDED-manufactured IN738 was composed of dense and fine dendrites. The higher laser powers of 800 W and 1000 W created higher temperature gradient within the molten pool, which promoted the epitaxial growth of dendrites. However, the long dendrites were prone to be torn apart under the transverse tensile stress, which was detrimental to the elongation and ductility. By comparison, when the laser power was 600 W, the growth direction of dendrites between adjacent layers was different and exhibited the best ductility.

Effect of processing parameters on the microstructure of laser-clad Stellite 6 on the X19CrMoNbVN11-1 stainless-steel substrate

This investigation aims to study the effect of laser cladding parameters on the microstructure of Stellite 6 on the X19CrMoNbVN11-1 stainless-steel substrate. First, Stellite 6 powder was coated on the X19CrMoNbVN11-1 substrate using the laser cladding method. The effect of laser cladding parameters (i.e., laser power, scanning speed, and powder feed rate) was studied on the microstructure of deposits. The secondary dendritic arm spacing was assessed, and the structural defects were studied (e.g., lack of bonding, porosity, and crack). The results revealed that the microstructure has changed from coating/substrate interface to coating surface, from plate-cellular to columnar and equiaxed dendrites. Also, an increase in the laser power increased the cellular structure in the coating/substrate interface and equiaxed dendrites in the coating surface. The cooling rate (G × R) increased by increasing the scanning and powder injection rates. The microstructure of the Stellite 6 was composed of cobalt solid-solution γFCC.

Anomalous twin boundary formation in magnesium alloys by rapid solidification

The aim of this work is to investigate the formation of an anomalously high fraction of twin boundaries (TBs) during laser directed energy deposition (DED) of a Mg-3Al-1 Zn (wt.%) alloy. With that goal, single tracks are deposited using different combinations of scan speed and powder feed rate. The melt pool dimensions are related to the DED parameters. Irrespective of the processing conditions, the resulting microstructures are always formed by fine grains with a very weak texture. However, some DED parameter combinations give rise to a fraction of TBs that is significantly higher than that corresponding to a random texture. These TBs are characterized by an irregular morphology and by the presence of segregated atoms, solute clusters, and nanoparticles. Additionally, the lattice in the vicinity of the TBs is highly distorted and contains a high population of stacking faults. All these characteristics set them apart from conventional tensile TBs, which exhibit a large degree of coherency and limited segregation. Rapid solidification is thus presented here as a novel avenue to design TBs with unique properties in Mg alloys. This work paves the way for future studies on grain boundary design via additive manufacturing methods, a field that is still in its infancy.

Effect of Abnormal Powder Feeding on Mechanical Properties of Fabricated Part in Directed Energy Deposition

Effect of Abnormal Powder Feeding on Mechanical Properties of Fabricated Part in Directed Energy Deposition

Investigation of Deposition Parameters for Near-Beta Alloy Ti-55511 Fabricated by Directed Energy Deposition

The directed energy deposition (DED) parameters were determined for near-β alloy Ti-55511 by employing statistical design of experiments (DOEs) methods. Parameters resulting in fully dense freeform deposits were identified using two sequential DOEs. Single laser tracks were printed with several laser power, traverse rate, and powder feed rate settings in an initial DOE to identify promising build parameters. The capture efficiency and effective deposition rate were used to characterize and rank the single track deposits. The best parameters were then used to print a solid cube with various X–Y and Z overlaps (different hatch spacing, HS, and layer thickness, ZS) in a second DOE. Suitable deposition parameters were selected based on the cube density and microstructure and were used to fabricate larger tensile samples for mechanical testing. Multiple parameter sets were found to provide dense Ti-55511 deposits with acceptable mechanical properties and the parametric models showed statistical significance.

Influences of makiang (Syzygium nervosum) seed powder on growth performance, immunological response, antioxidant and immune related gene expression in juvenile Nile tilapia (Oreochromis niloticus)

A makiang seed powder (MSP) feeding trial was performed on Nile tilapia (Oreochromis niloticus) for eight weeks to evaluate the effects on growth performance, immune response, and gene expression. Three hundred fingerlings (13.20 ± 0.04 g) were fed five diets with various amounts of MSP at 0, 5, 10, 20 and 40 g kg−1. After four and eight weeks of the feeding trial, growth rates and immune responses were tested, while relative immune and antioxidant gene expression were performed after eight weeks of MSP feeding. Accordingly, the growth indices (SGR, WG) and immune activity (skin mucus and serum lysozyme, skin mucus and serum peroxidase, alternative complement, phagocytosis and respiratory burst activities) in Nile tilapia were significantly increased in the treated diets compared with the control diet (P < 0.05). The maximum (P ≤ 0.05) growth and immune activity values were noted in fish fed 5 g kg−1 MSP. IL1, IL8, LBP, GPX, GSTa and GSR gene expressions were also shown to be upregulated in fish on MSP diets, with the highest value reported in fish fed 5 g kg−1 MSP. Finally, MSP has the potential to be employed as a feed supplement in the biofloc system for the cultivation of Nile tilapia.

Process parameter optimization for laser powder directed energy deposition of Inconel 738LC

Processing nickel-based superalloys is one of the major challenges in the additive manufacturing (AM) field. Nickel-based superalloys consist of several alloying elements, which make them prone to the formation of undesired phases and cracking due to the complex thermodynamics during the metal AM processes. In order to produce defect-free parts from nickel-based superalloys via metal AM processes, optimization of process parameters is required. In this study, the effect of laser powder directed energy deposition (LP-DED) process parameters on the geometrical properties and porosity ratio of Inconel 738 LC (low carbon) is investigated. Geometrical specifications, including the track height, width, and wetting angle are the major factors that indicate the quality of the final product. The analysis of variance (ANOVA) and response surface methodology (RSM) were developed in order to predict the geometrical specifications of single tracks from the key process parameters, namely laser power, scan speed, and powder feed rate. An optimum set of process parameters was obtained through multi-objective optimization by minimizing the porosity ratio, crack formation and maximizing the deposition rate. The results were verified and a good agreement with the experimental measurements was achieved. The produced bulk sample showed less than one percent porosity content, which indicates the effectiveness of single-track optimization prior to bulk sample production. The overall microstructure of the bulk sample showed a high content of MC carbides resulting from the abundance of alloying elements.

Incremental Feeding of Perovskite Powders: Angstrom‐Precision Growth for Single‐Source Solar Cell Fabrication

Vacuum‐based deposition of halide perovskites receives a lot of attention for its proven scalability and conformal depositions. Co‐evaporation has remarkable success, but efficiencies continue to lag behind their solution‐based counterparts. This is in part attributed to the complex sublimation behavior of some organic ammonium precursor salts and the increased complexity of the absorber materials, requiring the use of four or more sources in a conventional co‐evaporation setup. The latter has driven work into single‐source methods with flash evaporation presented as one such method. However, flash evaporation processes typically evaporate all material in a single batch, leading to short deposition times at high temperatures. Particle sputtering effects seen at these high temperatures drive processes toward low temperatures where prolonged exposure causes degradation. Here, a pulse‐driven incremental powder feeding system is presented. This method is capable of stable flash evaporation rates for &gt;1 h, with controlled rates as low as 1.5 Å per pulse (±0.89). The feasibility of this method is demonstrated for three different perovskite compositions: FAPbBr3, MAPbI3, and FA1−xMAxPbSnI3:SnF2. Furthermore, FAPbBr3 and MAPbI3 are integrated into all vacuum‐processed thin‐film solar cells leading to power conversion efficiencies (PCE) of ~4% and 10%, respectively.

Mechanical Behavior and Shape‐Memory Effects of NixTi1−x Alloys with Tunable Mixing of Ni/Ti Powders by Laser‐Directed Energy Deposition

As it is known, controlling NiTi alloy's microstructure is an urgent problem in additive manufacturing, which directly affects the mechanical properties of the alloy. In laser‐directed energy deposition (LDED) technology, the simultaneous powder feeding equipment with double powder barrels can effectively control the material ratio and realize the generation of NixTi1−x alloys with different atomic ratios. First, the performance differences of NiTi alloy under different thermal treatments are explored. Based on this, the optimal thermal treatment process is used to adjust the microstructure of NiTi alloy fabricated by LDED by changing the Ni/Ti atomic ratio to improve mechanical properties. The results indicate that Ni4Ti3 precipitates can induce the R phase, change the phase transition, and improve the mechanical properties in Ni‐rich NiTi alloys. Besides, the mechanical properties of NixTi1−x alloy can be enhanced by adjusting the Ni/Ti atomic ratio to change the content of Ni4Ti3 precipitates. Ni52Ti48 alloy has a tensile strength of 771 MPa, an elongation of 11.6%, and a recovery rate of 95.2%.

Surface modification of AZ61 Magnesium Alloy with Stelcar Alloy Powder Using Laser Cladding Technique

Objective: To examine the tribological and mechanical characteristics of the AZ61 alloy reinforced with Stelcar alloy powder by surface modification through laser cladding. Methods: Surface modification was done by using a laser cladding machine, where the input parameters including Scanning Speed (SS), Laser Power (LP) and Powder Feed Rate (PFR) were adjusted. Experimental design followed a L9 Taguchi approach, and optimization of input parameters for the surface modified AZ61 alloy reinforced with Stelcar alloy particles was achieved using Grey Relational Analysis (GRA). Output responses, namely wear volume and micro hardness were measured to assess the effectiveness of the optimization process. Findings: From the results obtained through the experiments, powder feed rate contributes to 82.81% of the variability in wear volume, whereas the laser power mostly impacts micro hardness; influencing it by 89.46% confirmed with ANOVA. In order to determine the optimal processing parameters among various objectives, this research applies the grey relational method. The results showed that the wear volume and micro hardness of the composite were significantly affected by the Stelcar reinforcement. Employing Grey relational analysis combined with several optimization objectives into a transparent method, resulting in a clad material with the lower wear volume and higher micro hardness. The optimized processing parameters predicted grey relational grades with an error rate of 1.39% and a significant contribution of 63.60% from laser power. This study confirmed that multi-objective optimization could enhance laser-cladded surface mechanical characteristics and laid out the theoretical foundation for this approach. Novelty: This study introduces an innovative approach to surface modification by employing the laser cladding technique to reinforce Stelcar alloy particles, thereby creating a dense coating on the substrate. Keywords: Laser Cladding, AZ61 magnesium alloy, Stelcar alloy, Coating, Optimization

EXPLORING EPITAXIAL GRAIN GROWTH AND MARANGONI-INDUCED CONVERSION IN COLUMNAR DENDRITES: A STUDY OF INCONEL 718 ADDITIVE MANUFACTURING VIA DIRECT LASER ENERGY DEPOSITION

This study characterizes the microstructure changes of Inconel 718 (IN718) by laser cladding (LC). Well-bonded pore-free, crack-free, single-layer, and multi-layer (overlapped) LC was done on IN718 with the same powder. The basic microstructure illustrates the presence of [Formula: see text], [Formula: see text], and [Formula: see text] -phases. The precipitation of an irregularly shaped laves phase was observed with dendritic grains in the top and bottom regions of the single-track LC. Further, the epitaxial grain growth of columnar dendrites was observed in the interdendritic region along the laves phase. High leveraging of quick-dissolving behaviors of the laves phase in multi-track LC enhances the high-temperature mechanical performance. Modified grain morphology of the multi-track LC in terms of size, shape, and orientation is reported. Columnar dendrites (short and long) are the most common grains, with varied sizes and orientations reported in line with the Marangoni effect. The microhardness at the top layer of single and multi-track exhibited a higher value of 490.6[Formula: see text]HV and 500.7[Formula: see text]HV, respectively, which is comparatively lower than the bottom layer of single and multi-track samples. The influencing process parameter over clad width is scan speed, and over clad height is powder feed. The nonlinear mathematical model is proposed with a reliability of 99.22% and 99.52% for clad width and height, respectively.

Comparative assessment of supervised machine learning algorithms for predicting geometric characteristics of laser cladded inconel 718

Laser cladding, an innovative surface modification and coating preparation process, has emerged as a research hotspot in material surface modification and green remanufacturing domains. In the laser cladding process, the interaction between laser light, powder particles, and the substrate results in a complicated mapping connection between process parameters and clad layer quality. This work aims to shed light on this mapping using fast evolving machine learning algorithms. A full factorial experimental design was employed to clad Inconel 718 powder on an A286 substrate comprising 64 groups. Analysis of variance, contour plots, and surface plots were used to explore the effects of laser power, powder feeding rate, and scanning speed on the width, height, and dilution rate of the cladding. The performance of the predictive models was evaluated using the index of merit (IM), which includes mean square error (MSE), mean absolute error (MAE), and coefficient of determination (R2). By comparing the performance of the models, it was found that the Extra Trees, Random forest regression, Decision tree regression, and XGBoost algorithms exhibited the highest predictive accuracy. Specifically, the Extra Trees algorithm outperformed other machine learning models in predicting the cladding width, while the RFR algorithm excelled in predicting the associated height. The DTR algorithm demonstrated the best performance in predicting the cladding dilution rate. The R2 values for width, height, and dilution rate were found to be 0.949, 0.954, and 0.912, respectively, for these three models.