The Influence of Laser Defocusing in Selective Laser Melted IN 625.

Alexandru Paraschiv,Tiberius Florian Frigioescu,Gheorghe Matache,Mihaela Raluca Condruz,Ion Ionică

doi:10.3390/ma14133447

Alexandru Paraschiv, Tiberius Florian Frigioescu + Show 3 more

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https://doi.org/10.3390/ma14133447

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Abstract

Laser defocusing was investigated to assess the influence on the surface quality, melt pool shape, tensile properties, and densification of selective laser melted (SLMed) IN 625. Negative (−0.5 mm, −0.3 mm), positive (+0.3 mm, +0.5 mm), and 0 mm defocusing distances were used to produce specimens, while the other process parameters remained unchanged. The scanning electron microscopy (SEM) images of the melt pools generated by different defocusing amounts were used to assess the influence on the morphology and melt pool size. The mechanical properties were evaluated by tensile testing, and the bulk density of the parts was measured by Archimedes’ method. It was observed that the melt pool morphology and melting mode are directly related to the defocusing distances. The melting height increases while the melting depth decreases from positive to negative defocusing. The use of negative defocusing distances generates the conduction melting mode of the SLMed IN 625, and the alloy (as-built) has the maximum density and ultimate tensile strength. Conversely, the use of positive distances generates keyhole mode melting accompanied by a decrease of density and mechanical strength due to the increase in porosity and is therefore not suitable for the SLM process.

Highlights

Selective laser melting (SLM) is one of the most promising laser powder bed fusion (LPBF) techniques that has gained increasing attention in the last decade because of its ability to produce customized and functional parts with a complex geometry that would be difficult or even impossible to produce with standard subtractive manufacturing technologies [1,2,3,4,5]
The process parameters are considered globally critical in the SLM process in terms of melt pool characteristics, mechanical properties, and density, and many studies have focused on optimizing them to maximize the potential of the SLM technology [4,8,9]
Values, the the melt melt pool was affected by the fluctuations from the thermocapillary convection and generated pool was affected by the fluctuations from the thermocapillary convection and generated an increase inin thethe case of negative distances, where the an increase of of the thesurface surfaceroughness, roughness,especially especially case of negative distances, where highest values were obtained

Summary

Introduction

Selective laser melting (SLM) is one of the most promising laser powder bed fusion (LPBF) techniques that has gained increasing attention in the last decade because of its ability to produce customized and functional parts with a complex geometry that would be difficult or even impossible to produce with standard subtractive manufacturing technologies [1,2,3,4,5].the lack of a full understanding of the impact of all process parameters on the quality of SLMed parts is still a limitation of this technology. The SLM machines use a small laser beam focus diameter of less than 100 μm when the laser has a power of up to 600 W and a larger laser beam focus diameter (100–500 μm) when the laser has a power of up to 1 kW. In both cases, there are several advantages and disadvantages

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