Estudo da caracterização microestrutural e da deformação plástica em temperatura criogênica da superliga inconel 718 produzida por manufatura aditiva

Abstract

This study investigated the behavior of Inconel 718 produced by Laser Powder Bed Fusion, using reused powder, subjected to room and cryogenic deformation and two different heat treatments. The results showed that the reused powder maintained suitable morphology, allowing for high densification and low porosity in the printed parts. Optimal printing parameters were established (scan speed of 1000 mm/s, hatch spacing of 80 μm, laser power of 40 W, and a 67° rotation between layers), resulting in a porosity as low as 0.09%. Two heat treatments were evaluated: solution treatment at 980 °C (S980) and at 1180 °C (S1180), both followed by aging. The treatment at 980 °C partially reduced the Laves phase and maintained columnar grains, while at 1180 °C it promoted a greater dissolution of this phase and the transformation to equiaxed grains, with aligned precipitation of carbides. After aging, hardness increased significantly, reaching 486 HV (S980E) and 416 HV (S1180E), compared to 302 HV in the as-built condition (AB). Mechanical testing at cryogenic temperatures revealed an increase in strength for all samples compared to room temperature, but only the AB condition preserved ductility. All fracture surfaces exhibited ductile features. The EBSD analysis indicated varying accumulations of defect density in the microstructure near the fracture surface. Work-hardening curves showed distinct behavior between ambient and cryogenic temperatures, highlighting a change in deformation and strengthening mechanisms, influenced by precipitates.