Welding Metallurgy of

A review of selective laser melting of aluminum alloys: Processing, microstructure, property and developing trends

Additive manufacturing (AM), also known as 3D printing or rapid prototyping, is gaining increasing attention due to its ability to produce parts with added functionality and increased complexities in geometrical design, on top of the fact that it is theoretically possible to produce any shape without limitations. However, most of the research on additive manufacturing techniques are focused on the development of materials/process parameters/products design with different additive manufacturing processes such as selective laser melting, electron beam melting, or binder jetting. However, we do not have any guidelines that discuss the selection of the most suitable additive manufacturing process, depending on the material to be processed, the complexity of the parts to be produced, or the design considerations. Considering the very fact that no reports deal with this process selection, the present manuscript aims to discuss the different selection criteria that are to be considered, in order to select the best AM process (binder jetting/selective laser melting/electron beam melting) for fabricating a specific component with a defined set of material properties.

Additive Manufacturing Processes: Selective Laser Melting, Electron Beam Melting and Binder Jetting-Selection Guidelines.

X-ray microcomputed tomography (microCT) has become an established method of testing and analyzing additively manufactured parts in recent years, being especially useful and accurate for d...

X-Ray microcomputed tomography in additive manufacturing : a review of the current technology and applications

Particle-reinforced metal matrix nanocomposites fabricated by selective laser melting : a state of the art review

A three-dimensional finite element model is proposed to study the effects of laser power and scan speed on the thermal behavior and melting/solidification mechanism during selective laser melting (SLM) of TiC/Inconel 718 powder system. The cooling time during powder delivery is taken into account to simulate the actual production process well. It shows obviously the existence of heat accumulation effect in SLM process and, the tailored set of cooling time of 10 ms during powder delivery alleviates that effectively. The maximum temperature gradient in the molten pool slightly increases from 1.30×104 °C/mm to 2.60×104 °C/mm as the laser power is increased from 75 W to 150 W. However, it is negligibly sensitive to the variation of scan speed. There is a positive corresponding relationship between the maximum rate of temperature change and processing parameters. A low laser power (75 W) or a high scan speed (300 mm/s) is more energy efficient in Z-direction of the molten pool, giving rise to a deep-narrow cross section of the pool. Whereas, a high laser power (150 W) or a low scan speed (50 mm/s) causes a shallow-wide cross section of the molten pool, meaning it is more energy efficient in the Y-direction of the melt. The combination of a laser power of 125 W and a scan speed of 100 mm/s contributes to achieve a sound metallurgical bonding between the neighbor layers and tracks, due to the proper molten pool size (width: 109.3 µm; length: 120.7 µm; depth: 67.8 µm). The SLM experiments on TiC/Inconel 718 powder system are performed to verify the reliability and accuracy of the physical model and, simulation results are proved to be correct.

Effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of TiC/Inconel 718 composites

The WC/Inconel 718 composites were fabricated by selective laser melting (SLM). The laser processing parameters played an important role in determining the microstructure and performance of the WC/Inconel 718 composite parts. With the decrease in the laser scanning speed, the densification rate increased and achieved 97.8% at a scanning speed of 350 mm/s. As an optimal scan speed of 450 mm/s was applied, the WC/Inconel 718 composite part obtained a mean microhardness as high as 393.2 HV 0.1 . At the same time, a regular and orderly gradient interface with a mean thickness of 0.27 μm surrounded by a diffusion layer was obtained. What is more, the chemical composition of the gradient interface and the diffusion layer were X 3 C 17 and XC 4 (X = W, Ni, Cr, Fe), respectively. Meanwhile, the composite acquired a considerably low coefficient of friction (COF) of 0.35 with almost no fluctuation and attendant wear rate of 2.5 × 10 − 4  mm 3  N − 1  m − 1 and the wear mechanism changed continuously from severe abrasive wear to adhesive wear. Subsequently the effects of the tailored gradient interface on wear performance were discussed. It revealed that the existence of gradient interface showed a very important role in improving the wear performance of the SLM-processed WC/Inconel 718 composite parts.

Effects of tailored gradient interface on wear properties of WC/Inconel 718 composites using selective laser melting

Relation of microstructure, microhardness and underlying thermodynamics in molten pools of laser melting deposition processed TiC/Inconel 625 composites

A heterogeneous catalyst CuO–CeO2 with a hollow structure was successfully synthesized by assembling CuO on the outer surface of CeO2 hollow spheres through a layer-by-layer deposition strategy. Further reduction under a H2 atmosphere was carried out to modify its surface state, resulting in sample r-CuO–CeO2. The catalysts were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform-infrared spectroscopy (FT-IR). SEM and TEM showed that the synthesized catalysts had a hollow sphere structure, which can expose more active sites and promote mass transfer. The results of XPS revealed that the content of Cu0&Cu+ increased from 13.6 to 19.0% after H2 reduction, which was conducive to the activation of terminal alkyne to promote the annulation/A3-coupling reaction. The conversion of this cascade reaction with the r-CuO–CeO2 catalyst can reach more than 95%, while the value was only 55% by using CuO–CeO2 as a catalyst. Moreover, the r-CuO–CeO2 catalyst showed a good recycle property and group compatibility in the general applicability of the cascade annulation/A3-coupling reaction, providing a series of propargylamine derivatives in good chemoselectivity. 

Hollow CuO–CeO2 Nanospheres for an Effectively Catalytic Annulation/A3-Coupling Reaction Sequence

The invention relates to the technical field of consumable materials (metal power as raw materials) for 3D printers, in particular to a Fe-based composite powder preparation method and equipment capable of directly generating FeN reinforced phases. The method comprises the steps of placing iron blocks in a confined space, feeding circulating nitrogen into the confined space, and laser scanning andvaporizing the iron blocks in the circulating nitrogen atmosphere, so that nitrogen reacts with the vaporized iron blocks to generate Fe-based power with FeN phases. Through the in-situ reaction method, the reinforced phases are directly generated in the powder in the powder-making process, and the problem of poor contact between reinforced particles and base materials in the prior art is solved.

Sainan Cao

Papers

Effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of TiC/Inconel 718 composites

Effects of tailored gradient interface on wear properties of WC/Inconel 718 composites using selective laser melting

Relation of microstructure, microhardness and underlying thermodynamics in molten pools of laser melting deposition processed TiC/Inconel 625 composites

Hollow CuO–CeO2 Nanospheres for an Effectively Catalytic Annulation/A3-Coupling Reaction Sequence

Fe-based composite powder preparation method and equipment capable of directly generating FeN reinforced phases