A low-cost parametric finite element thermal model is proposed to study the impact of the initial powder condition, such as diameter and packing density, on effective thermal conductivity as well as the impact of the laser power input on the final temperature distributions during selective laser melting (SLM). Stainless steel 304L is the material used, since it is not yet commercially available in SLM equipment and our main goal was to show the capabilities of the finite element method in the evaluation of power input in the process. The results from our sensitivity analysis showed that packing density has a greater impact on the final temperature distributions compared with powder diameter variance. However, overall the thermal conductivity of the powder only showed significant effects below the melting point, otherwise the thermal conductivity no longer affected the temperature distributions. Among the three different power inputs analyzed, the temperature profile demonstrated that power inputs of 100 and 200 W are recommended when printing SS-304L rather than 400 W, which generates too high temperature in the powder bed, a non-favorable behavior that can induce high residual stresses and material evaporation.

Selective Laser Melting (SLM) process is a Powder Bed Fusion (PBF) technique, which has shown significantly growth in the recent years. The demand for this process is justified by the versatility and ease in manufacturing the parts from 3D models as well for the increased complexity of engineered parts generated from topology or shape optimization. Automotive, aerospace, medical and aviation industries are taking great advantage of this process due the unique geometry characteristics found in the components. To enhance the benefits of SLM, a vital task is to analyze the laser power input impact on the temperature distribution through the powder bed, important for posterior residual stresses analysis. The Finite Element Method proposed in this study is a transient thermal model, able to predict temperature distribution through different sections of the powder bed when performing a single track of the laser scanning. Furthermore, the impact of the laser power input is carried out utilizing SS 304L, a low cost Stainless Steel alloy that can be employed in the SLM process, in order to determine the influence on the temperature distribution along the different cross sections.

Metal powder properties in Selective Laser Melting (SLM) is among one of the most important factors when implementing new alloy developments for the equipment. In fact, not all commercially available metal powder alloys are ready to be implemented without a comprehensive set of tests. Besides the powder properties, we have a large number of building and environmental parameters that demands extensively research prior implementation. Although selected alloys are commercially available and documented to be used in SLM, including Ti6Al4V, SS316L and In718, the majority of it still not ready to be utilized in this system. The focus of this study is to use a thermal model in order to predict the thermal distribution of the process regarding different aspects of the powder properties, especially the thermal conductivity, when different powder packing densities and diameters are used. A Stainless Steel 304L will be utilized in this work, since it is not yet available to be commercially used. The main goal is to show the capabilities of the Finite Element Method in the pre-definition of optimal parameters for the process using a new alloy development. Our findings can be used as a pre-evaluation guideline when printing SS304L, since the comparison with similar experimental work in the field showed significant resemblance and outcomes. The temperature distributions show that the packing density has greater sensibility on the final temperature distributions, compared to the powder diameter variance. Two different power inputs are compiled and the temperature outcomes demonstrate that a power input of 100 Watts is recommended to use when printing SS304L, rather than 400 Watts that brings high temperature into the powder bed.

Several parameters are defined before the Selective Laser Melting printing process, which may depend on the manufacturer of the equipment, but in general, we commonly encounter hatch distance, scanning speed, layer thickness, laser power input, scanning strategy, overlap distance, and substrate preheating temperature as the parameters that mainly define the printing process. The last parameter is the focus of this study, which is applied to a finite element model to simulate temperature distributions over one layer thickness of the powder bed. The substrate temperature and power input affect the cooling rates and temperature gradients imposed on the powder bed, consequently influencing the component’s final property, surface finishing, and accuracy (dimensioning tolerances). The current FEM model showed that the preheat substrate temperature played different roles depending on which power input is used; however, there is an observed trend that is the reduction in temperature gradients in the powder bed overall when higher substrate temperatures are used.