Corrosion behavior of laser directed energy deposited SS316L/Inconel718 functionally graded materials

Functionally graded material (FGM) can exhibit a variety of excellent properties by controlling layer-by-layer gradients in composition and microstructure. In this paper, SS316L/Inconel718 FGM was fabricated by laser directed energy deposition (LDED) to investigate the microstructures and corrosion behaviors at the transitional interfaces. The results indicate that the microstructures in gradient regions along the build direction include cellular crystals, dendritic structures, columnar crystals, and equiaxed crystals. With increasing mass fraction of IN718, the precipitates within the FGM matrix transition from metal oxides to Laves phases and MC phases, accompanied by elemental segregation of Nb and Mo at the grain boundaries. The enhanced corrosion resistance is attributed to the increased pitting corrosion resistance elements within the FGM matrix. Additionally, the high content of Cr2O3 and NiO in the passive film enhance the corrosion resistance. The SKP and LEIS test results indicate that the LDED-manufactured SS316L/IN718 FGM exhibits no apparent galvanic coupling corrosion and maintains excellent corrosion resistance transition. This investigation offers a reference for the study of corrosion-resistant composite materials.