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This study’s novel 13Ni400 maraging steel parts are additively manufactured through a selective laser melting process. The Taguchi approach is adopted to evaluate the combined influence of process variables (energy density), viz., laser power, layer thickness, hatch spacing, and scan speed, on responses like relative density, microhardness, surface roughness, and tensile strength. The powder and material characterization studies are conducted in terms of an optical microscope, scanning electron microscope (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and fractography analysis to explore the pre- and post-fabrication scenarios of the build parts. The consequences of energy density and process variables are studied through meticulous parametric studies. Finally, the optimum level of built parameters is identified and validated by a confirmative test predicting an average error of ~1.80%. This work is proficient in producing defect-free parts with maximum densification and improved mechanical properties for newly developed 13Ni-400 maraging steel by the selective laser melting (SLM) technique.

In this study, microelectrical discharge machining (μEDM) is used for drilling microholes on a thin sheet of Ti Grade 2 alloy of thickness 50 μm using a tungsten carbide (WC) microtool of diameter 470 μm. The main focus of the study is to understand the electrical and nonelectrical μEDM parameters on the accuracy, precision, and machining efficiency of drilled holes. The controllable process factors such as capacitance, voltage, tool rotation, and feed rate are considered when conducting the experiments based on a Taguchi L16 orthogonal array. The main effect and interaction contour plots have been prepared to investigate the influence of the process parameters on the response measures like material removal rate, overcut, circularity, and taper angle of the drilled holes. Analysis of variance (ANOVA) has been carried out to study the percentage contribution and significance of each process parameter on the performance measures. The micrographic images reveal the quality of the profiles and edges of the drilled holes. Further, the Overall Evaluation Criterion (OEC) is applied for multiparameter optimization. [ABSTRACT FROM AUTHOR]

The effective fabrication of materials using selective laser melting depends on the process parameters. Here, we analyse the suitability of the energy density to represent the energy transferred to the powder bed, which is effectively used to melt the particles and to produce the bulk specimens. By properly varying laser power and speed in order to process the powder at constant energy density, we show that the equation currently used to calculate the energy density gives only an approximate estimation and that hatch parameters and material properties should be considered to correctly evaluate the energy density.

Tungsten heavy alloy composite was developed by using novel CoCrFeMnNi high-entropy alloy as the binder/reinforcement phase. Elemental tungsten (W) powder and mechanically alloyed CoCrFeMnNi high-entropy alloy were mixed gently in high energy ball mill and consolidated using different sintering process with varying heating rate (in trend of conventional sintering < microwave sintering < spark plasma sintering). Mechanically alloyed CoCrFeMnNi high-entropy alloy have shown a predominant face-centered cubic (fcc) phase with minor Cr-rich σ-phase. Consolidated tungsten heavy high-entropy alloys (WHHEA) composites reveal the presence of Cr−Mn-rich oxide phase in addition to W-grains and high-entropy alloys (HEA) phase. An increase in heating rate restricts the tungsten grain growth with reduces the volume fraction of the Cr−Mn-rich phase. Finally, spark plasma sintering with a higher heating rate and shorter sintering time has revealed higher compressive strength (~2041 MPa) than the other two competitors (microwave sintering: ~1962 MPa and conventional sintering: ~1758 MPa), which may be attributed to finer W-grains and reduced fraction of Cr−Mn rich oxide phase.