Characterization of Inconel 718 fabricated by Selective Laser Melting (SLM) to achieve more productive parameters

The aim of this project, as the title suggests, is to study and improve the parameters used to produce Inconel 718 with the ‘’PrintSharp250’’. PrintSharp 250 is an SLM (Selective Laser Melting) machine, owned by Prima Additive, capable of transforming metal powder into 3d objects. This thesis will be divided into 5 chapters. A general introduction to Additive Manufacturing is reported in the first one: ‘’State of Art’’. In this chapter the cycle that characterizes this innovative process and the 3 main AM techniques used in the field of metals is presented. The chapter also includes a general review of the material Inconel 718 and the work done with it in the additive manufacturing field. From chapter 2, the experimental part of the thesis and the methods used for the characterization and study of the produced samples are described in detail. The experimental part can be divided into three phases. In the first phase 20 combinations of process parameters that characterize the L-PBF (Laser Powder Bed Fusion) techniques are defined. The choice of the parameters sets, called Design of the Experiment, was performed comparing the experience of Prima Additive in this field and the data found in literature about the Inconel718 fabricated by SLM. The purpose of this first phase was to identify the relation between the porosity percentage of the samples and the Volumetric Energy Density values used to print them. Once identified the most promising parameters sets the repeatability were tested. Same samples were printed again to see if the porosity percentage of this second job is consistent with the previous one. After checking the repeatability, the focus of the experiment moved on productivity. In the second phase, in fact, a second DoE was created with the purpose of decrease the building time of the process. The hatching distance, the laser power and the scanning velocity were modified with the aim to maintain the Volumetric Energy Density in the same range that showed the best results in terms of porosity during the first DoE. At the end of the analysis the two most promising sets of parameters in terms of productivity were selected. For the sake of simplicity, we defined a ‘’optimized set of parameters 1’’ and ‘’ optimized set of parameters 2’’. The third phase of the thesis is dedicated to the mechanical properties of parts produced with these optimized parameters: three bars for each one were printed and tested. In addition, also 3 bars produced with the standard parameter in use in Prima Industrie were printed to have a comparison between the optimized parameters and the standard ones in terms of Ultimate Tensile Strength and Yield Strength. At the end of the experiments, in the chapter 5, a case of study is presented in order to highlight the big advantages that the use of optimized parameters can lead to, both in terms of time and of costs. Finally, the chapter 6 summarizes the conclusion of the whole work and presents some possible future works that could be carried on in the future.