Enhanced thermal stability and interfacial bonding in laser additively manufactured diamond/CuSn10 grinding tools via WXC/Co-Coated diamond particles

Scratch and wear resistance of additive manufactured 316L stainless steel sample fabricated by laser powder bed fusion technique

Optimizing laser additive manufacturing process for Fe-based nano-crystalline magnetic materials

Texture evolution during high strain-rate compressive loading of maraging steels produced by laser powder bed fusion

Concurrent improvement of strength and ductility in heat-treated C300 maraging steels produced by laser powder bed fusion technique

In Additive Manufacturing (AM) using the Laser Powder Bed Fusion (L-PBF) technique, spherical powders are the most commonly preferred for direct sintering. However, composites such as cemented carbides and heavy alloys often exhibit irregular shapes. Due to the requirement for extremely fine grain size, the cohesive behavior of the particle bed becomes significant, influencing its compressibility and porosity. These physical properties result in powders with coarse textures, which lead to low fluidity and interruptions in material flow within the ducts. This study evaluates the flowability of WC and W refractory materials combined with Co and Ni. Key interparticle properties, including real and bulk density, bulk compressibility and porosity, and granular shear, were analyzed to understand their influence on the deposition layer behavior in the powder bed. These parameters are crucial for understanding the micro-behavior of granular materials and correlating it with their macro-behavior. The rheological aspects of these composite powders are discussed, aiming to establish correlations between the manufacturing process and the resulting properties of their mixtures.

Additive manufacturing of maraging steel-H13 bimetals using laser powder bed fusion technique

The success in metal matrix composites (MMCs) fabrication by laser powder bed fusion (L‐PBF) technique has opened doors to further advanced materials development. But the drive to produce fully dense MMCs from a combination of metal and ceramic materials still faces serious setbacks arising from the associated complex phenomena and defects formation. This article discusses some of the issues that encourage defects generation in particulate‐reinforced MMCs. It further presents an overview of the additive manufacturing (AM) defects influenced by reinforcement addition and mitigation strategies. The review seeks to broaden the scope of L‐PBF fabrication defects concerning MMCs, and give a perspective on tailor designing feedstock materials for AM fabrication of high‐quality MMCs. Powder particles segregation, inappropriate scanning strategy, and combine effect of influencing parameters (processing and material) and defects are issues not often accounted for that encourage processing defects in MMCs. A holistic approach that accounts for all the controllable and materials related parameters, irrespective of their negligible influences on the optimal processing window, is expected to enhance the quality of L‐PBF‐fabricated MMCs. Furthermore, tailor designing of the feedstock materials may offer enhanced reinforcement material dispersion within the matrix and help reduce attendant defects from uneven reinforcement particles dispersion.

A layered hybrid lattice structure consisting of a body-centered cubic (BCC) structure and an N-type structure with a negative Poisson's ratio effect is designed. In order to assess the effect of the position and number of N-type structure layers in the overall lattice structure on the mechanical properties, three kinds of hybrid lattice structures with different positions and numbers of N-structure layers are manufactured by using laser powder bed fusion (LPBF) technique. Compression experiments are carried out on the three kinds of layered hybrid lattice structures and the BCC lattice structure for comparisons. The entire loading process is recorded and the deformation pattern of the lattice structure is captured. The experimental results show that the presence of the N-type structure has a significant effect on the deformation pattern of the lattice structure. Comparing the mechanical response and energy absorption efficiency, it is found that the hybrid lattice structure performs better than the BCC structure when the structural strain is small. In addition, finite element models of the N-type structure unit-cell and hybrid lattice structures are established. Numerical simulations are conducted to verify the negative Poisson's ratio behavior of the N-structure and predict the deformation modes of the layered hybrid lattice structure.

Mechanical properties of AlSi12 alloy, which was manufactured by laser powder bed fusion (LPBF) technique, were investigated. Some basic properties of fabricated objects such as density and tensile strength were clarified. The suitable laser irradiation condition of fabricated objects that had own high relative density was showed. The microstructure of fabricated objects with as-manufactured condition was also evaluated. The fabricated objects exhibited the similar ultimate tensile strength and the Young’s modulus according to the building directions, although other mechanical properties slightly differed. Mechanical properties of fabricated objects made by reused powders also exhibited the similar values of those manufactured by unused powders. In contrast, the mechanical properties excluding the Young’s modulus of the fabricated objects, which were annealed, differed due to annealing treatment. Furthermore, the mechanical properties excluding the Young’s modulus of the fabricated objects for the designed shapes manufactured to the tensile test specimen were smaller than those of the fabricated objects machined from LPBFed rectangular block. Therefore, the attention is necessary for the mechanical design of fabricated object through LPBF technique and that with annealing treatment, because of the difference in the mechanical properties between the object built as the designed shape and the object made from LPBFed bulk product.

Preparation of ultrahigh-strength and ductile nano-lamellar eutectic high-entropy alloy via laser powder bed fusion

Additive manufacturing of Mn-Al permanent magnets via laser powder bed fusion

Grinding tools with superabrasive grains can be manufactured from different bond materials. In several industrial applications, metallic bond systems are used. In general, these show good grain retention and offer a high thermal conductivity, when compared to the other widely used bond types such as vitrified and resin bonds. One drawback of the metallic bond is the lack of pores in the grinding layer. This is caused by the manufacturing processes that are typically used, like brazing or hot pressing. These generally produce very dense layers. The high density and low porosity lead to comparatively little space for the transport of lubricant, coolant, and chips. One approach to eliminate this disadvantage is to introduce cavities into the grinding layer, using the laser powder bed fusion technique (LPBF). In order to evaluate the general suitability of LPBF in combination with the bond material and diamond grains, grinding layer samples with a nickel-titanium bond were produced. The abrasive behavior of these samples was tested in scratch tests on cemented carbide to verify the applicability as grinding tools. While the diamond grains in the powder mixture are not part of the fusion process, they also did not interfere with the manufacturing process, and the scratch tests showed promising abrasive capabilities. The grinding layer itself withstood the process forces, and no grain breakout could be observed. This indicates that the grain retention forces are high enough for the grinding process and that NiTi has a high potential as a bonding material for the manufacturing of grinding tools via LPBF.

This work aimed to study one of the most important challenges in orthopaedic implantations, known as stress shielding of total shoulder implants. This problem arises from the elastic modulus mismatch between the implant and the surrounding tissue, and can result in bone resorption and implant loosening. This objective was addressed by designing and optimising a cellular-based lattice-structured implant to control the stiffness of a humeral implant stem used in shoulder implant applications. This study used a topology lattice-optimisation tool to create different cellular designs that filled the original design of a shoulder implant, and were further analysed using finite element analysis (FEA). A laser powder bed fusion technique was used to fabricate the Ti-6Al-4V test samples, and the obtained material properties were fed to the FEA model. The optimised cellular design was further fabricated using powder bed fusion, and a compression test was carried out to validate the FEA model. The yield strength, elastic modulus, and surface area/volume ratio of the optimised lattice structure, with a strut diameter of 1 mm, length of 5 mm, and 100% lattice percentage in the design space of the implant model were found to be 200 MPa, 5 GPa, and 3.71 mm−1, respectively. The obtained properties indicated that the proposed cellular structure can be effectively applied in total shoulder-replacement surgeries. Ultimately, this approach should lead to improvements in patient mobility, as well as to reducing the need for revision surgeries due to implant loosening.

Austenitic stainless steels produced by Laser Powder Bed Fusion (L-PBF) are interesting materials because of their excellent corrosion resistance. Due to their relatively low hardness, the tribological response of these materials is poor, which limits their use in applications where control of wear degradation is important. Nevertheless, low-temperature plasma-assisted carburisation is an interesting process for improving the wear resistance of austenitic stainless steels, as has been observed for wrought materials. In fact, the increase in hardness is guaranteed by a surface layer of expanded austenite (S-phase) with a thin top layer of amorphous carbon. In this work, AISI 316 L, produced by the L-PBF technique, was carburised using 5 different plasma gas mixtures (by varying the CH4/H2 ratio) at 475°C for 7 hours. The samples obtained were then subjected to a detailed microstructural characterisation in order to obtain information on surface modification. The morphological features of the surface were examined by SEM observations in top view and in cross-section. The tribological performance was evaluated by pin-on-flat tests (alumina sphere as counter-material) with 2 different applied loads and a stroke length of 5 mm. Friction coefficient, wear rate (stylus profilometer) and wear mechanisms (SEM) were also evaluated. Preliminary results show an increase in wear resistance of all plasma treated materials compared to the untreated material. The improved tribological performance was discussed in relation to the abrupt increase in surface hardness.

The Al/W composite layer was fabricated on the surface of the aluminum alloy using laser alloying technology to enhance the current-carrying wear resistance. Additionally, the current-carrying wear behaviors of the Al/W composite layer and the aluminum alloy substrate were investigated under different currents. The results indicate that the presence of hard phases such as W and Al4W in the composite layer significantly enhanced the wear resistance of the material. Specifically, the average friction coefficient of the Al/W composite layer under different currents was reduced by approximately 9.3-35.8% compared to the aluminum alloy substrate, and the wear rate under current-carrying conditions decreased by about 1.9-6.0 times. For the aluminum alloy substrate, adhesive wear is the dominant mechanism under currents ranging from 0 to 60 A. However, as the current increased to 80 A, the severity of arc erosion intensified, and the wear mechanism transitioned to a combination of arc erosion and adhesive wear. In contrast, for the Al/W composite layer, abrasive wear was the dominant wear mechanism in the absence of electrical current. Upon the introduction of the current, the wear mechanism changed to a coupling effect of arc erosion and adhesive wear.