Abstract
To manufacture custom medical parts or scaffolds with reduced defects and high mechanical characteristics, new research on optimizing the selective laser melting (SLM) parameters are needed. In this work, a biocompatible powder, 316L stainless steel, is characterized to understand the particle size, distribution, shape and flowability. Examination revealed that the 316L particles are smooth, nearly spherical, their mean diameter is 39.09 μm and just 10% of them hold a diameter less than 21.18 μm. SLM parameters under consideration include laser power up to 200 W, 250–1500 mm/s scanning speed, 80 μm hatch spacing, 35 μm layer thickness and a preheated platform. The effect of these on processability is evaluated. More than 100 samples are SLM-manufactured with different process parameters. The tensile results show that is possible to raise the ultimate tensile strength up to 840 MPa, adapting the SLM parameters for a stable processability, avoiding the technological defects caused by residual stress. Correlating with other recent studies on SLM technology, the tensile strength is 20% improved. To validate the SLM parameters and conditions established, complex bioengineering applications such as dental bridges and macro-porous grafts are SLM-processed, demonstrating the potential to manufacture medical products with increased mechanical resistance made of 316L.
Highlights
Nowadays, selective laser melting (SLM) is one of the most used additive manufacturing (AM)technologies applied to produce directly metallic prototypes from virtual models
Due to the low costs of 316L stainless steel compared to titanium or CoCr alloys, it is frequently applied to the manufacture of dental ramus blades, ramus frame implants [16], customized dental
The purpose of this paper is to identify the SLM parameters able to manufacture, in a stable process, medical applications with high tensile strength made of 316L powder
Summary
Selective laser melting (SLM) is one of the most used additive manufacturing (AM). The main defects that can occur in these complex applications are typical for SLM manufacturing such as macro- and microscopic cracks, gas voids, heat-affected zones or a residual stress phenomenon These technological defects are a consequence of rapid melting and cooling cycles and new research on optimizing the SLM process parameters for 316L powder is needed to limit them. Different companies are providing 316L powder but full details regarding the particle size, distribution, shape or flowability are not conferred This information is essential in adequate preparation and controlling of SLM process because at high levels of irradiation energy, the fine particles of 316L can evaporate, generating porosity and decreasing the mechanical characteristics. Due to extended processability investigation, the novelty of this research relates to an increased mechanical resistance of parts made of 316L powder, SLM-manufactured by common solid laser limited to 200 W
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