Selective laser sintering of Mo-CuNi composite to be used as EDM electrode

Abstract

Purpose -This work is focused on the investigation of direct production of electrical discharge machining (EDM) electrodes through the selective laser sintering (SLS) technique using a new metal-matrix composite material made of molybdenum and a copper-nickel alloy (Mo-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. Additionally, EDM experiments are performed to evaluate the electrodes performance under different machining conditions. The paper aims to discuss these issues. Design/methodology/approach -The new EDM electrode material used was a powder system composed of Mo and pre-alloyed CuNi. A systematic experimental methodology was designed to evaluate the effects of layer thickness, laser scan speed and hatch distance. The densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and solid copper electrodes EDMachined under the same conditions. Findings -The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and an adequate combination of parameters can produce parts with good quality. The laser scan speed has a great effect on the densification behavior of the samples, while the effect of hatch distance on the porosity is more visible when the overlapping degree is considered. The overlapping also had a significant effect on the surface morphology. The EDM results showed that the Mo-CuNi electrodes had superior performance to the copper powder electrodes made by SLS for all the EDM regimes applied, but inferior to those achieved with solid copper electrodes. Originality/value -Significant results on the direct SLS manufacturing of a new material which has a great technological potential to be used as an EDM electrode material are presented. Valuable guidelines are given in regard to the SLS optimization of Mo-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

“…Similar results for the influence of layer thickness on the porosity and layer bonding have been obtained in other studies [21]. It was concluded that smaller layer thickness leads to stronger bonding between the layers and decreases the porosity of the parts.…”

“…This is caused by the longer interaction time between the powder and the laser beam, which boosts the rate of energy delivered to the powder bed [21]. A higher laser scan speed results in less energy transferred to the materials [22], leading to less sintering and in turn to more porosity.…”

“…It should be noted that this case occurs especially in low melting point systems. Increasing the energy delivered to the powder bed promotes better melting of the powders, enabling more liquid phase to flow and infiltrate into the voids between the particles, which can lead to a denser structure [21]. …”

“…If a too-small layer thickness is chosen, the blade will drag non-melted large particles or chunks of melted particles, displacing the previous sintered layers from their position. Consequently, layer thickness for denser product must be set to the minimum layer thickness and vice versa [21]. …”

Selective Laser Melting of Magnesium and Magnesium Alloy Powders: A Review

“…It was observed that the relative densities of the parts decreased with increase in both the scanning speed and hatch spacings. At a constant laser power (p = 200 W), decreasing the scanning speed caused a longer dwelling time of the laser beam on the surface of the molten pool, thereby boosting the laser energy density delivered to the powder bed resulting in better densification [82]. Hatch spacing which is also called "scan spacing" is another important parameter that determines the degree of overlap of the laser spot when a new laser line scans over the previously scanned line.…”