Search

Purpose: This paper aims to investigate the differences in hot corrosion behavior of the GTD222 superalloy and TiC/GTD222 composite in a mixed salt of 75% Na2SO4 and 25% K2SO4 at 900°C. Design/methodology/approach: The GTD222 superalloy and TiC/GTD222 nickel-based composite were prepared using selective laser melting (SLM). Subsequently, the hot corrosion behavior of the two alloys was systematically investigated in a salt mixture consisting of 75% Na2SO4 and 25% K2SO4 (Wt.%) at 900°C. Findings: The TiC/GTD222 composite exhibited better hot corrosion resistance compared to the GTD222 superalloy. First, the addition of alloying elements led to the formation of a protective oxide film on the TiC/GTD222 composites 20 h before hot corrosion. Second, TiC/GTD222 composite corrosion surface has a higher Ti content, after 100 h of hot corrosion, the composite corrosion surface Ti content of 10.8% is more than two times the GTD222 alloy 4% Ti. The Ti and Cr oxides are tightly bonded, effectively resisting the erosion of corrosive elements. Originality/value: The hot corrosion behavior of GTD222 superalloy and TiC/GTD222 composites prepared by SLM in a mixed salt of 75% Na2SO4 and 25% K2SO4 was studied for the first time. This study provides insights into the design of high-temperature alloys resistant to hot corrosion. [ABSTRACT FROM AUTHOR]

In this study, the effects of laser power on the microstructure and mechanical properties of Inconel 718 formed by SLM were systematically studied. The results show that with the increase in laser power from 285 W to 360 W, the increase in working temperature in the molten pool promoted the evaporation of gas and the vaporization of the low-melting-point alloy components, and the relative density gradually increased from 99.31% to 99.79%. In addition, with the increase in laser energy density, the microstructure gradually coarsened from columnar dendrites to cellular crystals. The nano-hardness of the material decreased with the increase in laser power. The nano-hardness of four groups of samples from 285 W to 360 W decreased form 3.43 GPa to 2.09 GPa, and the elastic modulus decreased form 205.72 GPa to 199.91 GPa. [ABSTRACT FROM AUTHOR]

This review is focused on the perspectives of the application of Advanced High Strength Steels (AHSSs) in the field of additive technologies directed at the laser powder bed fusion/selective laser melting processes. In principle, AHSSs require significant attention due to their promising mechanical properties for usage in the automotive industry towards reducing the weight of vehicles. Although additive manufacturing represents a promising perspective towards expanding the industrialization of AHSSs in a wider area of their applications, they have not been sufficiently investigated concerning their usage in LPBF/SLM processes. AM techniques enable the fabrication of complex machine parts, including those with a cellular structure, which can contribute to further reducing the weight of vehicles or structures. Maraging steels have recently attracted the attention of researchers, and today are a common grade of steel produced by LPBF techniques. The other group of AHSSs are high-Mn steels with an austenitic matrix characterized by the TRIP and TWIP effects. Less published research has been conducted on medium-Mn steels, which require additional intercritical annealing and preheating during printing. Moreover, the advanced bainitic steels and low-density, high-strength steels represent a new window for further research into the use of the LPBF processes for their fabrication. [ABSTRACT FROM AUTHOR]

This study assesses the geometric distortion of cantilevers fabricated from stainless steel 316L with varying internal structures using Selective Laser Melting (SLM) technology. The cantilevers were printed under identical conditions and subsequently post-processed with Wire Electrical Discharge Machining (WEDM) and heat treatment. The geometric deviations were evaluated using a micrometer and a Coordinate-Measuring Machine (CMM). This research underscores the importance of internal structure selection and post-processing in enhancing the geometric accuracy and mechanical stability of 3D-printed slender structures from stainless steel. By demonstrating that internal geometries can significantly influence the end product's structural performance, the findings provide valuable insights for the design and engineering of Additive Manufactured (AM) components, particularly in applications that involve bending. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) has been widely used for coating metal bone implants. However, HA coating may separate from the metal substrates, resulting in poor performance such as inflammatory reactions which may finally lead to implant failure. Dispersing HA into metal substrate may be a viable solution but such a composite may suffer from inferior mechanical strength. Therefore, a functionally graded material (FGM) with HA dispersing in metal substrate in gradients is introduced to increase surface osteogenic capability and simultaneously maintain a good mechanical strength of the bone implant. In this study, Ti6Al4V(Ti64)-HA composite with different component of HA and their corresponding FGMs were fabricated by selective laser melting (SLM). It was demonstrated that compared with the pure Ti64 and Ti64-2.5%HA composite, Ti64-1%HA composite seemed to have a better osteogenic promoting property in vitro. Both the FGMs significantly promoted the osteogenic activities of the pure Ti64 in vivo. Moreover, functionally graded structure improved the anti-compression properties of composites. [ABSTRACT FROM AUTHOR]

Laser-based powder bed fusion of metals (PBF-LB/M) is a widely used additive manufacturing process characterized by a high degree of design freedom. As a result, near fully dense complex components can be produced in near-net shape by PBF-LB/M. Recently, the PBF-LB/M process was found to be a promising candidate to overcome challenges related to conventional machining of the Fe64Ni36 Invar alloy being well known for a low coefficient of thermal expansion (CTE). In this context, a correlation between process-induced porosity and the CTE was presumed in several studies. Therefore, the present study investigates whether the unique thermal properties of the PBF-LB/M-processed Fe64Ni36 Invar alloy can be tailored by the selective integration of defects. For this purpose, a full-factorial experimental design, representing by far the largest processing window in the literature, was considered, correlating the thermal expansion properties with porosity and hardness. Furthermore, the microstructure and mechanical properties were investigated by scanning electron microscopy and quasi-static tensile tests. Results by means of statistical analysis reveal that a systematic correlation between porosity and CTE properties could not be determined. However, by using specific process parameter combinations, the microstructure changed from a fine-grained fan-like structure to a coarse columnar structure. [ABSTRACT FROM AUTHOR]

Nowadays, the use of metal processing additive technologies is a rapidly growing field in the manufacturing industry. These technologies, such as metal 3D printing (also known as additive manufacturing) and laser cladding, allow for the production of complex geometries and intricate designs that would be impossible with traditional manufacturing methods. They also offer the ability to create parts with customized properties, such as improved strength, wear resistance, and corrosion resistance. In other words, these technologies have the potential to revolutionize the way we design and produce products, reducing costs and increasing efficiency to improve product quality and functionality. One of the significant advantages of these metal processing additive technologies is a reduction in waste and environmental impact. However, there are also some challenges associated with these technologies. One of the main challenges is the cost of equipment and materials, which can be prohibitively expensive for small businesses and individuals. Additionally, the quality of parts produced with these technologies can be affected by factors such as printing speed, temperature, and post-processing methods. This review article aims to contribute to a deep understanding of the processing, properties, and applications of ferrous and non-ferrous alloys in the context of SLM to assist readers in obtaining high-quality AM components. Simultaneously, it emphasizes the importance of further research, optimization, and cost-effective approaches to promote the broader adoption of SLM technology in the industry. [ABSTRACT FROM AUTHOR]

7050 aluminium alloy is widely used in aerospace industry due to its excellent mechanical properties. 7050 aluminium alloy belongs to Al–Zn–Mg–Cu alloy. Due to the formation of cracks in selective laser melting (SLM) forming of Al–Zn–Mg–Cu alloys, 7050 aluminium alloy is difficult to be applied to forming and manufacturing in this technological field. In order to solve this critical problem, in this paper, titanium dioxide (TiO2) powder was mixed with 7050 aluminium alloy using ball milling method to achieve the effect of eliminating cracks. The cracks in the specimens completely disappeared when the TiO2 additions were 1.5 wt% and 2 wt%. With the addition of TiO2, the grains gradually changed from coarse columnar crystals to fine equiaxed crystals. Combined with the temperature field simulation, the grain refinement and crack elimination mechanism of TiO2 in SLM forming were analysed. The grain refinement is attributed to the formation of Al3Ti. The crack elimination was attributed to the reduction of the intergranular solid-liquid channel length. The maximum values of tensile strength and elongation of 7050 aluminium alloy formed by SLM are achieved at 2 wt% of TiO2. The values are 389 MPa and 8.8 %. The better mechanical properties were attributed to the synergistic effect of crack elimination, Hall-Petch, and Orowan strengthening. This study provides experimental guidance for the preparation of crack-free 7050 aluminium alloy.

Exploring shape memory alloys (SMAs) is like diving into a world of material magic, especially when combined with additive manufacturing techniques. This detailed assessment delves into the fascinating realm of additive manufactured SMAs, examining their complex fabrication processes, captivating internal structures, wide-ranging applications, and unique properties. It is remarkable to observe how the combination of metals, particularly nickel and titanium, creates the very essence of SMA's capabilities and various other material combination for novel SMAs. Additional insights are provided regarding how additive manufacturing parameters and appropriate post-treatments can enable these materials to accomplish extraordinary functionalities. These SMAs also possess the ability to recollect and move, demonstrating superelasticity and the capacity to regain their original shape in various capacities. However, there are promising prospects for the development of novel SMA mixtures, enhanced post-treatments methods, and even more intelligent and responsive products with dimensional accuracy and uniformity. This work presents insights on opportunities in industries for resilient materials, ranging from everyday devices to the immense expanse of space and the human body. Even with the advancements, there is still work to be done in continuously improving their design and pocket comfort. This review not only presents information but also envisions a future in which additive manufactured SMAs are central to advancements in engineering and other fields.

A powder-bed-based additive manufacturing process called electron beam melting (EBM) is defined by high temperature gradients during solidification, which produces an extremely fine microstructure compared to the traditional cast material. However, porosity and segregation defects are still present on a smaller scale which may lead to a reduction in mechanical properties. It is important to have a better knowledge of the influence of post-fabrication treatments on the microstructure and mechanical characteristics before the use of additive manufacturing parts in specific applications. In this study, the effects of solution heat treatment (SHT) and hot isostatic pressing (HIP) on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by the EBM process have been investigated. The SHT and HIP treatments can significantly improve the ductility of EBM Ti-6Al-4V due to the coarsening of α laths and the formation of β grains.

The present study investigates the synergistic enhancement of hot corrosion resistance (900 °C, 75%Na2SO4+25%NaCl) and mechanical properties of IN738LC alloy prepared by selective laser melting after heat treatment. The results indicate that the M23C6 precipitation at the grain boundaries coupled with smaller-sized γ′ phase distribution in the inner grain is conducive to the formation of thicker Cr2O3 outer layer and Al2O3 inner layer for the samples, which effectively hinders the diffusion of S and Cl elements penetrate to the matrix, enhancing the hot corrosion resistance. Additionally, the presence of small-sized γ′ phase and re-crystallization-induced grain refinement contribute to an increase in yield strength (σYS = 1261 MPa) and ultimate tensile strength (σUTS = 1360 MPa) for the alloy.

Selective laser melting (SLM) offers the advantages of a short production cycle and high material utilization in manufacturing components with complex geometric features. It is extensively utilized in aerospace, medical, and energy fields. The accuracy of SLM formed workpieces usually cannot directly meet the requirements, and micro-milling can significantly improve surface accuracy. However, an unreasonable micro-milling process can lead to issues like high energy consumption and compromised surface morphologies of chip and workpiece. In this paper, the relationship between effective specific cutting energy, chip morphology, and surface morphology in the micro-milling process of additive manufacturing workpiece, Inconel 718 formed by SLM, is studied, and the process optimal selection based on energy efficiency is explored. This study is an innovative exploration that bridges the relationship between energy consumption and machining quality in micro milling of additively manufactured parts. The results show that energy efficiency will increase with the increase in feed per tooth and spindle speed. Moreover, when f/r increases, the chip length and width increase significantly from 78.3 μm to 0.35 μm–395.6 μm and 2.76 μm, respectively, and the energy efficiency gradually increases to nearly 100%. At the same time, the surface roughness initially decreases and then increases, indicating that increasing the spindle speed can reduce surface roughness and improve surface quality. Based on analyzing the relationship between energy efficiency and surface morphologies of chip and workpiece, the optimal selection of micro-milling process parameters for SLM Inconel 718 is explored to ensure that the process considers both energy efficiency and surface morphologies. This work sheds new light on understanding the cutting mechanism of the micro-milling process of additive manufacturing part, providing theoretical support for future research on relationship between energy efficiency and surface morphologies in micro-milling.

In the present work, the influence of defects on the compressive response of octet‐truss AlSi10Mg lattice structure specimens produced with a selective laser melting process is investigated. The defect population in one cell, in two cells, and cubic specimens composed of 27 cells has been assessed with micro‐computed tomography (micro‐CT) analyses. The statistical distributions of the characteristic defect sizes, i.e., the equivalent diameter, the volume, and the surface, assessed in the lattice structure specimens and in volumes randomly extracted from a rectangular bar have been compared. Finally, the compressive behavior of lattice structure specimens has been simulated with a simplified damage‐tolerant finite element model accounting for the influence of defects and compared with experimental results. The analyses have proven that the defect population in volumes extracted from a rectangular bar can provide reliable simulated results, even if micro‐CT inspections of a unit cell or specimens made of several cells are suggested. Highlights: Manufacturing defects strongly influence the structural integrity of lattice structures.Defect volume, surface, and equivalent diameter are reliable characteristic defect sizes.The defect population should be assessed on multiple cells for damage‐tolerant design.Finite element analyses should model the influence of defect size. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is a rapidly evolving technology that requires extensive knowledge and management for broader industrial adoption due to the complexity of phenomena involved. The selection of parameters and numerical analysis for the SLM process are both costly and time-consuming. In this paper, a three-dimensional radial basis function-finite difference (RBF-FD) meshless model is introduced to accurately and efficiently simulate the molten pool size and temperature distribution during the SLM process for austenitic stainless steel (AISI 316L). Two different volumetric moving heat source models were presented, namely the ray-tracing method heat source model and the double-ellipsoidal shape heat source model. The temperature-dependent material properties and phase change process were also considered, based on experiments and effective models. Results of the model for the molten pool size were validated with those of the literature. The proposed approach can be used to predict the effect of different laser power and scan speed on the molten pool size and temperature gradient along the depth direction. The result reveals that the depth of the molten pool is more sensitive to laser power than scan speed. Under the same scan speed, a 22% change in laser power (45 ± 10 W) affects the maximum temperature proportionally by about 9%. The developed algorithm is computationally efficient and suitable for industrial applications. [ABSTRACT FROM AUTHOR]

This study investigated the temperature dependence of IN718 corrosion behavior in 3.5 wt. % NaCl solution, comparing conventionally rolled (Roll) and SLM-manufactured (SLM) samples. While both exhibited degradation with increasing temperature, the Roll sample presented a significantly higher susceptibility to corrosion by increasing the temperature from 25 to 70 °C. Rapid corrosion current density (icorr) of the Roll sample, which increased from 0.25 to 1.3 μA cm2, suggested the preferential γ-matrix dissolution and microgalvanic attack triggered by Laves phases and carbides acting as preferential dissolution sites. Conversely, the SLM sample showcased less segregation and fewer carbide phases due to its high cooling rate, resulting in a milder icorr rise (0.45–0.6 μA cm2). The findings hold promise for a more comprehensive understanding of IN718 performance and can guide the selection of optimal fabrication methods for components exposed to corrosive and high-temperature environments. [ABSTRACT FROM AUTHOR]

The mechanical properties of 10Kh12N10Т and 08Kh18N9 stainless steel components in additive manufacturing are investigated. Selective laser melting (SLM) and wire arc additive manufacturing (WAAM) are considered. Components produced by selective laser melting are found to be stronger than those produced by wire arc additive manufacturing. Additional heat treatment reduces the strength but improves the plasticity, especially in wire arc additive manufacturing. The influence of structural porosity on the mechanical properties of the components is assessed. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) technologies enable near-net-shape designs and demand-oriented material usage, which significantly minimizes waste. This points to a substantial opportunity for further optimization in material savings and process design. The current study delves into the advancement of sustainable manufacturing practices in the automotive industry, emphasizing the crucial role of lightweight construction concepts and AM technologies in enhancing resource efficiency and reducing greenhouse gas emissions. By exploring the integration of novel AM techniques such as selective laser melting (SLM) and laser metal deposition (LMD), the study aims to overcome existing limitations like slow build-up rates and limited component resolution. The study's core objective revolves around the development and validation of a continuous process chain that synergizes different AM routes. In the current study, the continuous process chain for DMG MORI Lasertec 65 3D's LMD system and the DMG MORI Lasertec 30 3D's was demonstrated using 316L and 1.2709 steel materials. This integrated approach is designed to significantly curtail process times and minimize component costs, thus suggesting an industry-oriented process chain for future manufacturing paradigms. Additionally, the research investigates the production and material behavior of components under varying manufacturing processes, material combinations, and boundary layer materials. The culmination of this study is the validation of the proposed process route through a technology demonstrator, assessing its scalability and setting a benchmark for resource-efficient manufacturing in the automotive sector. [ABSTRACT FROM AUTHOR]

Aluminum–air batteries are characterized as "green energy for the 21st century" due to their clear advantages in terms of high current discharge, high specific energy, low cost, and easy-to-obtain electrode materials. This study develops the SLM aluminum anode quality prediction model and evaluates its learning and training results using the BP neural network architecture. By altering the network topology of the SLM aluminum anode quality prediction model, we create a process parameter backpropagation model that takes advantage of the extremely adaptable capabilities of artificial neural networks. The quick and exact selection of process parameters meets the goals of density, self-corrosion current, and anode usage, hence improving the forming quality and processing efficiency of SLM aluminum anodes. The experimental results show that the process parameter backpropagation model's parameter configurations match to the real densities and self-corrosion currents, which are somewhat higher than the specified target values. The maximum error rate for the aluminum anode forming quality prediction model is 8.23%. Furthermore, the actual anode utilization rate is somewhat lower than the projected target value, indicating that the backpropagation model can satisfy actual production needs. [ABSTRACT FROM AUTHOR]

The utilization of 3D printing metals has gained considerable traction as a manufacturing technique within the automotive and aerospace sectors, leading to a demand for more efficient and cost-effective methods. In this article, the connecting rod (CR) of the two-wheeler's four-stroke engine underwent a redesign, analysis, and printing process using SS17-4PH gas atomized stainless steel powder through selective laser melting (SLM). The redesign aimed to reduce weight while maintaining strength in SolidWorks. Ansys 18.1® was used to perform finite element analysis (FEA). A comparison was made between the overall deformation, elastic strain, Von-Mises stress, safety factor, life, damage, and weight reduction of the optimized CRs and the original CR. The analysis was conducted under a load of 616 N, which is double the actual load on the CR. Subsequently, the optimized CR was printed using SLM. The study revealed that the weight of the optimized CR is significantly lower than that of the original. Furthermore, the modified CR is expected to have a similar lifespan to the original CR. [ABSTRACT FROM AUTHOR]

Lattice structures have emerged as promising materials for aerospace structure applications due to their high strength-to-weight ratios, customizable properties, and efficient use of materials. These properties make them attractive for use in anti-ice systems, where lightweight and heat exchange are essential. This paper presents an extensive experimental investigation into mechanical compression properties of lattice trusses fabricated from AlSi10Mg powder alloy, a material commonly used in casted aerospace parts. The truss structures were manufactured using the additive manufacturing selective laser melting technique and were subjected to uniaxial compressive loading to assess their performance. The results demonstrate that AlSi10Mg lattice trusses exhibit remarkable compressive strength with strong correlations depending upon both topology and cells' parameters setup. The findings described highlight the potential of AlSi10Mg alloy as a promising material for custom truss fabrication, offering customizable cost-effective and lightweight solutions for the aerospace market. This study also emphasizes the role of additive manufacturing in producing complex structures with pointwise-tailored mechanical properties. [ABSTRACT FROM AUTHOR]

Three-cycle minimum surface structures show excellent lightweight and energy absorption capabilities, and additive manufacturing techniques provide a unique degree of freedom for lattice structure design. Therefore, in this study, three-period minimum surface (TPMS) structures of Schwarz-P boron steel alloys were prepared by Selective Laser Melting (SLM) technique. By investigating the effect of lattice structure design, we have analyzed the deformation behavior, mechanical properties and energy absorption capacity under compression. In addition, tensile properties and fracture morphology were analyzed to gain insight into the performance characteristics of these structures, and the effect of structural design on hardness was explored. The results of the study show that the structural design has a small effect on the microstructure and hardness. Under compressive loading, the P (0.5 1) structure exhibits a uniform deformation behavior, while the other four structures show a crushing deformation pattern. In particular, the P (0.5 1) structure exhibits excellent compressive performance, with an energy absorption work per unit mass as high as 296.2 J/mm^3, and its stiffness reaches 1627 MPa. Meanwhile, the P (0.35 1) structure exhibits excellent tensile performance with the tensile strength of 687 MPa. The morphological analysis of the tensile fracture reveals that the fracture mainly occurs in the strut nodes, and it mainly exhibits ductile tensile fracture.

This study offers significant insights into the multi-physics phenomena of the SLM process and the subsequent porosity characteristics of ZK60 Magnesium (Mg) alloys. High-speed in-situ monitoring was employed to visualise process signals in real-time, elucidating the dynamics of melt pools and vapour plumes under varying laser power conditions specifically between 40 W and 60 W. Detailed morphological analysis was performed using Scanning-Electron Microscopy (SEM), demonstrating a critical correlation between laser power and pore formation. Lower laser power led to increased pore coverage, whereas a denser structure was observed at higher laser power. This laser power influence on porosity was further confirmed via Optical Microscopy (OM) conducted on both top and cross-sectional surfaces of the samples. An increase in laser power resulted in a decrease in pore coverage and pore size, potentially leading to a denser printed part of Mg alloy. X-ray Computed Tomography (XCT) augmented these findings by providing a 3D volumetric representation of the sample internal structure, revealing an inverse relationship between laser power and overall pore volume. Lower laser power appeared to favour the formation of interconnected pores, while a reduction in interconnected pores and an increase in isolated pores were observed at higher power. The interplay between melt pool size, vapour plume effects, and laser power was found to significantly influence the resulting porosity, indicating a need for effective management of these factors to optimise the SLM process of Mg alloys.

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability. [ABSTRACT FROM AUTHOR]

The potential of digital image analysis based on the Segment Anything Model (SAM) in analyzing the morphology of single tracks obtained by selective laser melting (SLM) is considered. A digital microscope produces images of single tracks obtained at different scanning speeds and different laser source power. The images are automatically analyzed: the single tracks are classified by external appearance and their width is recorded. The quality of the initial digital images and the presence of thermal influence zones significantly affect the agreement of the measurements obtained by automatic analysis and the measurements obtained by microscopy of transverse sections. [ABSTRACT FROM AUTHOR]

Determining the thermal stress in selective laser melting (SLM) of a metal–powder composite within a single layer requires the solution of an auxiliary problem: analysis of the nonsteady heating of an isotropic half-space by a mobile laser source. The results are used in creating a surface influence function for a thermoelastic half-space. [ABSTRACT FROM AUTHOR]

This study examined the compatibility of an orthopedic implant made from polyamide 12 sintering, coupled with a composite made from Ti6Al4V/ST316L laser fusion, both in vitro and in vivo. SLM 3D printing was used to construct the composite implant of Ti6Al4V/ST316L, while SLS 3D printing was used for the polyamide 12 implant. SEM analysis, X-ray diffraction analysis, and energy dispersive spectroscopy (EDS) were used to characterize the fabricated implants. Mechanical properties of the implants were evaluated using a universal testing machine. Using finite element modeling, von Mises stresses within implants and human bones could be examined. It involved increasing the cell count and implanting MC3T3-E1 preosteoclasts on implants for a week. Biocompatibility was determined using an AlamarBlue® fluorescence test. After six weeks of implantation, rabbit femurs were stained with Hematoxylin and Eosin to determine in vivo biocompatibility of the implant. Based on the findings, both the polyamide 12 implant and the Ti6Al4V/ST316L composite SLM-3D printed by SLS-3D printing were biocompatible. Finite element analysis revealed that the maximum Von Misses stress was within acceptable limits. [ABSTRACT FROM AUTHOR]

This study offers significant insights into the multi-physics phenomena of the SLM process and the subsequent porosity characteristics of ZK60 Magnesium (Mg) alloys. High-speed in-situ monitoring was employed to visualise process signals in real-time, elucidating the dynamics of melt pools and vapour plumes under varying laser power conditions specifically between 40 W and 60 W. Detailed morphological analysis was performed using Scanning-Electron Microscopy (SEM), demonstrating a critical correlation between laser power and pore formation. Lower laser power led to increased pore coverage, whereas a denser structure was observed at higher laser power. This laser power influence on porosity was further confirmed via Optical Microscopy (OM) conducted on both top and cross-sectional surfaces of the samples. An increase in laser power resulted in a decrease in pore coverage and pore size, potentially leading to a denser printed part of Mg alloy. X-ray Computed Tomography (XCT) augmented these findings by providing a 3D volumetric representation of the sample internal structure, revealing an inverse relationship between laser power and overall pore volume. Lower laser power appeared to favour the formation of interconnected pores, while a reduction in interconnected pores and an increase in isolated pores were observed at higher power. The interplay between melt pool size, vapour plume effects, and laser power was found to significantly influence the resulting porosity, indicating a need for effective management of these factors to optimise the SLM process of Mg alloys. [ABSTRACT FROM AUTHOR]

The prediction of porosity is a crucial task for metal based additive manufacturing techniques such as laser powder bed fusion. Short wave infrared thermography as an in-situ monitoring tool enables the measurement of the surface radiosity during the laser exposure. Based on the thermogram data, the thermal history of the component can be reconstructed which is closely related to the resulting mechanical properties and to the formation of porosity in the part. In this study, we present a novel framework for the local prediction of porosity based on extracted features from thermogram data. The framework consists of a data pre-processing workflow and a supervised deep learning classifier architecture. The data pre-processing workflow generates samples from thermogram feature data by including feature information from multiple subsequent layers. Thereby, the prediction of the occurrence of complex process phenomena such as keyhole pores is enabled. A custom convolutional neural network model is used for classification. The model is trained and tested on a dataset from thermographic in-situ monitoring of the manufacturing of an AISI 316L stainless steel test component. The impact of the pre-processing parameters and the local void distribution on the classification performance is studied in detail. The presented model achieves an accuracy of 0.96 and an f1-Score of 0.86 for predicting keyhole porosity in small sub-volumes with a dimension of (700 × 700 × 50) µm3. Furthermore, we show that pre-processing parameters such as the porosity threshold for sample labeling and the number of included subsequent layers are influential for the model performance. Moreover, the model prediction is shown to be sensitive to local porosity changes although it is trained on binary labeled data that disregards the actual sample porosity. [ABSTRACT FROM AUTHOR]

The feasibility of manufacturing high-performance components with complex structures is limited due to cracks in some superalloys fabricated by selective laser melting (SLM). By controlling the main process parameters such as scanning strategy, the adverse effects of cracks can be effectively reduced. In this paper, the effects of two different SLM scanning strategies with island and 'back-and-forth' and post-heat treatment on the cracks and mechanical properties of selective-laser-melted (SLMed) K438 alloy were investigated. The results show that the SLM method of the 'back-and-forth' scanning strategy had better lap and interlayer rotation angles and a more uniform distribution of laser energy compared with the island scanning strategy. The residual stress accumulation was reduced and crack formation was inhibited under this scanning strategy owing to the cooling and shrinkage process. In addition, the dislocation motion was hindered by the formation of uniformly dispersed MC carbides and γ' phases during the SLM K438 alloy process, which resulted in the density of the as-built SLMed K438 alloy being up to 99.34%, the hardness up to 9.6 Gpa, and the tensile strength up to 1309 MPa. After post-heat treatment, the fine secondary γ' phases were precipitated and dispersed uniformly in the Ni matrix, which effectively improved the Young's modulus and tensile strength of the alloy by dispersing the stress-concentrated area. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) of heat-resistant nickel alloy VZh159 is used to show that at constant energy density the key factor determining the texture and the internal stresses is the hatching distance. At multiple increase in the exposure rate and decrease in the hatching distance, the micropore proportion increases exponentially due to enhancement of the dissipation of the laser radiation caused by reflection in the track overlapping zone. [ABSTRACT FROM AUTHOR]

Analysis of published data on the effect of the exposure algorithms, energy, and scanning speed on the geometric characteristics of the molten pool and its fine structure, on the texture and grain structure of metallic materials synthesized by selective laser melting (SLM) is presented. A regression model describing the correlation between the required laser energy density and the powder composition characteristic temperatures during SLM of heat-resistant nickel- and cobalt-based alloys is obtained. [ABSTRACT FROM AUTHOR]

Although experimental research demonstrates the feasibility of processing glass via selective laser melting (SLM), achieving SLM precision manufacturing of fused silica is still a challenging but promising field. Therefore, a numerical model was developed in this work to predict the densification kinetics of glass powder monolayer under SLM, which provided a simulation tool for the optimization design of processing parameters. To be particular, the relative neck diameter and density of the powder bed under SLM were calculated using a cluster model to simulate the degree of consolidation, from which the thermal diffusivity of the powder bed was determined and the corresponding results of heat transfer were obtained through the numerical model implemented by using finite difference method (FDM). The experimental results for the SLM of glass with different processing parameters from other references validated the simulation results with a prediction error of less than 2%. Hence, the effects of processing settings, such as the influence of particle size and preheating temperature, could be accurately investigated by using this numerical modelling method. It was found that using powders with smaller particle sizes and setting a higher preheat temperature could improve the manufacturing quality of the obtained glass parts. From the densification results of the numerical modelling, we also introduced a novel optimization criterion, which could be utilized to optimise the processing parameters and fabricate the high-purity glass parts via SLM. [ABSTRACT FROM AUTHOR]

Samples produced from AlSi10Mg alloy powder by three-dimensional printing (selective laser melting) with different parameters are experimentally investigated. The samples produced are tested in extension, compression, and three-point flexure. The test results are graphically displayed. [ABSTRACT FROM AUTHOR]

Additive manufacturing makes the production of bulk metallic glasses possible in thicknesses exceeding the critical casting thickness. However, a crucial challenge is the build-up of thermally induced stress, often resulting in printed parts suffering from cracking. In this study, the process parameters are optimised for printing soft-magnetic metallic glass samples of an Fe-based alloy (Fe73.8P10.6Mo4.2B2.3Si2.3C6.7), using laser beam powder bed fusion. In addition, the structural and magnetic properties of as-received and heat-treated powder are investigated and compared to those of the printed samples. Kerr microscopy is used for imaging the magnetic domains on single track cross-sections produced on top of a polished printed sample. This reveals the shape of the melt pool of a single laser track, as well as the magnetic domains around it and in other regions of the printed sample. The shape and size of the magnetic domains reflect the residual stress in the sample through the effect of magneto-elastic coupling. This magnetic contrast could be used to get further insights into how to control the development of stress during the printing process.

Structural morphology, defects, compressibility and permeability properties studied by finite element analysis, selective laser melting technology and micromorphology, mainly to analyze the effect of porosity on the performance of porous skeletal scaffolds. The results showed that during the preparation process, there are construction errors. The designed structures were able to meet the requirements of cancellous and cortical bone in terms of compressive stress and elastic modulus. The compressive stresses of the diagonal cubic compact row and octahedron are more similar at the same porosity, the elastic modulus and compressive stress decrease with increasing porosity for three structures. In the hydrodynamic analysis, the maximum flow velocity appears in octahedron up to 0.001m/s. Permeability increases with increasing porosity for all structures. The maximum permeability was obtained at 75% porosity for all structures, the pressure drop for three structures at this porosity was most similar to that of natural bone (4.153 E3 N/m3).

Objectives: This study aimed to evaluate the effect of multiple baking cycles of porcelain on its shear bond strength to a cobalt-chromium (Co-Cr) alloy that is three-dimensionally printed using Selective Laser Melting (SLM) technique. Materials and methods: The research sample comprised forty-eight discs measuring 5 mm × 3 mm, divided into four groups according to: the manufacturing method (SLM, casting) and the number of porcelain baking cycles (1, 3) as follows: Group A: Co-Cr alloy by SLM with one baking cycle; Group B: Co-Cr alloy by SLM with three baking cycles; Group C: Ni-Cr alloy by casting with one baking cycle; Group D: Ni-Cr alloy by casting with three baking cycles. Then, porcelain was melted on disks, shear testing was performed and the values of the Shear Bond Strength (SBS) in MegaPascals (MPa) were calculated. Results: The mean SBS values for each group were (A: 25.69 - B: 19.51 - C: 35.72 - D: 28.67 MPa). Statistical analysis showed that the manufacturing method and the number of porcelain baking cycles had a significant influence on shear bond durability (P > 0.05): the strength of this bond decreased when baking cycles increased. The Co-Cr samples manufactured by SLM also showed a decrease in binding strength compared to the Ni-Cr samples made by casting. Conclusion: Repeated baking of porcelain reduces the strength of the porcelain bond with the Co-Cr alloy made by Selective Laser Melting (SLM) technique.

The study in this work fully utilized the computational advantages of various numerical methods and established a SPH-PFM coupling model for the 316 L SLM process. The temperature field, melt pool changes, and microstructure evolution of the 316 L SLM process were simulated and calculated. The correctness of the simulation results was verified through the comparison with experiments, and a calculation platform for melt pool evolution and microstructure simulation of metal material SLM process with independent intellectual property rights was developed. (1) Establish the mathematical model required for the dynamic simulation of the molten pool in the metal material SLM process based on the SPH method. (2) Extract the temperature field data and molten pool shape from the calculation results based on the SPH method, and then substitute them into the phase field model for molten pool modeling. The formation mechanism of the microstructure morphology inside the molten pool and the micro-segregation mechanism of solute elements at different positions during solidification were analyzed and discussed. The article compared the simulation results with the experimental results. The simulation results showed good consistency with the experimental results in terms of primary dendrite spacing, secondary dendrite spacing, and melt pool microstructure morphology, proving the correctness of the model established in this article. At the same time, the SPH-PFM coupling model established in this article can effectively solve the problem of predicting the microstructure of the melt pool in the SLM process, providing a new method for the study of microstructure prediction in the SLM process.

The use of additive technology—in particular, selective laser melting (SLM)—in producing wire electrodes for electrical discharge machining is considered. By this means it is possible to produce electrodes of high precision and complex geometry, with distinctive properties. In addition, the results of topological optimization in electrode design are presented. Topological optimization permits the production of wire electrodes that are more efficient in the given operating conditions. It is shown that, on the basis of additive technology and optimized electrode geometry with internal supply channels for dielectric liquid, the removal of sludge from the machining area may be improved, with consequent stabilization of the machining process. [ABSTRACT FROM AUTHOR]

This research addresses the metallurgical and mechanical response during the annealing of Ti6Al4V parts fabricated by selective laser melting. The as-manufactured Ti6Al4V exhibited a very fine α´ martensitic structure with low ductility of less than 10%. It was observed that the fine α´ martensitic structure transformed into two phases of α and β by applying heat treatments at 850 and 1020 °C followed by furnace cooling. The experimental results demonstrated that 850°C/2h/FC heat treatment has optimum mechanical performance in terms of tensile strength and ductility.

In this study, the effects of laser power on the microstructure and mechanical properties of Inconel 718 formed by SLM were systematically studied. The results show that with the increase in laser power from 285 W to 360 W, the increase in working temperature in the molten pool promoted the evaporation of gas and the vaporization of the low-melting-point alloy components, and the relative density gradually increased from 99.31% to 99.79%. In addition, with the increase in laser energy density, the microstructure gradually coarsened from columnar dendrites to cellular crystals. The nano-hardness of the material decreased with the increase in laser power. The nano-hardness of four groups of samples from 285 W to 360 W decreased form 3.43 GPa to 2.09 GPa, and the elastic modulus decreased form 205.72 GPa to 199.91 GPa.

This review is focused on the perspectives of the application of Advanced High Strength Steels (AHSSs) in the field of additive technologies directed at the laser powder bed fusion/selective laser melting processes. In principle, AHSSs require significant attention due to their promising mechanical properties for usage in the automotive industry towards reducing the weight of vehicles. Although additive manufacturing represents a promising perspective towards expanding the industrialization of AHSSs in a wider area of their applications, they have not been sufficiently investigated concerning their usage in LPBF/SLM processes. AM techniques enable the fabrication of complex machine parts, including those with a cellular structure, which can contribute to further reducing the weight of vehicles or structures. Maraging steels have recently attracted the attention of researchers, and today are a common grade of steel produced by LPBF techniques. The other group of AHSSs are high-Mn steels with an austenitic matrix characterized by the TRIP and TWIP effects. Less published research has been conducted on medium-Mn steels, which require additional intercritical annealing and preheating during printing. Moreover, the advanced bainitic steels and low-density, high-strength steels represent a new window for further research into the use of the LPBF processes for their fabrication.

Nowadays, the use of metal processing additive technologies is a rapidly growing field in the manufacturing industry. These technologies, such as metal 3D printing (also known as additive manufacturing) and laser cladding, allow for the production of complex geometries and intricate designs that would be impossible with traditional manufacturing methods. They also offer the ability to create parts with customized properties, such as improved strength, wear resistance, and corrosion resistance. In other words, these technologies have the potential to revolutionize the way we design and produce products, reducing costs and increasing efficiency to improve product quality and functionality. One of the significant advantages of these metal processing additive technologies is a reduction in waste and environmental impact. However, there are also some challenges associated with these technologies. One of the main challenges is the cost of equipment and materials, which can be prohibitively expensive for small businesses and individuals. Additionally, the quality of parts produced with these technologies can be affected by factors such as printing speed, temperature, and post-processing methods. This review article aims to contribute to a deep understanding of the processing, properties, and applications of ferrous and non-ferrous alloys in the context of SLM to assist readers in obtaining high-quality AM components. Simultaneously, it emphasizes the importance of further research, optimization, and cost-effective approaches to promote the broader adoption of SLM technology in the industry.