Estudo in situ utilizando radiação síncroton do aço inoxidável 316L produzido por manufatura aditiva.

Abstract

Test specimens of AISI 316L austenitic stainless steel were fabricated by Additive Manufacturing (AM). Mechanical and microstructural behavior were investigated by tensile tests with in situ X-ray diffraction accomplished in a thermomechanical simulator situated in the XTMS station of LNLS, located in CNPEM. Three conditions were studied: 316L AM as-built, 316L AM after annealing heat treatment, and 316L asrolled (for comparison). The effect of hydrogen and negative temperatures were studied during uniaxial tensile tests. These conditions are applied to this type of material in several industry sectors. The use of this steel in the oil and natural gas industry stands out. Once the microstructure obtained by AM is more refined and has different morphologies when compared to conventional processes, the study of the performance presented by parts made by AM is very important for its correct implementation and substitution of the subtractive manufacturing. Hydrogen leads to the embrittlement of components produced by the conventional process. For parts built by AM, it may not occur, depending on the parameters used, due to the microstructural refinement and phase transformation. In this work, the results showed that there was no hydrogen embrittlement in the AM samples. It was observed similar levels of UTS for the AM as-built condition and an increase of 17.9% of UTS for the heat-treated condition. There was an increase of 40.7% and 55.1% in strain for the AM as-built and AM heat-treated conditions, respectively. For the as-rolled condition, it was observed a low influence of hydrogen in the mechanical behavior. In cryogenic temperatures, an increase of toughness occurs owing to activation of other deformation mechanisms, partial suppression of dynamic recovery (due to low temperature), and phase transformations, which can be observed in rolled specimens as well as in AM parts.