Characterization and Impact of Thermal Conductivity of Stainless Steel 316L Employed in Additive Manufacturing

The main objective of this research was to develop new methods to improve the mechanical properties of 3D printed metal parts by controlling the heat transfer mechanisms involved in the melting and solidification of powder particles. A number of experiments were carried out to study the parameters involved in the process. The first part of the work was dedicated to the measurement of effective thermal conductivity in 316L stainless-steel powder. The results showed that controlled samples had important increments in thermal conductivity. The experimental setup was based on a steady-state analysis, designed to safely expose the sample up to 1000 C. The best result was obtained from the 10% compacted sample, whose thermal conductivity was double that of the reference sample. In the second part of this work, simulations were performed of a laser track over a powder bed. The results obtained from the thermal conductivity experiments were compared with those from analytical models. The thermal behaviour of the powder displayed an important decrement in temperature gradients. Moreover, analysis of subsequent laser tracks showed important improvements under low energy density. In summary, the theorical findings of this work can help to reduce and control defects formed in the melting and solidification stages of the manufacturing process by limiting temperature gradients and improving thermal distribution.