Effect of the scanning strategy in the laser directed energy deposition process of SS316L-Inconel 625 FGM bulk

In this research, two effective types of scanning strategies in the laser directed energy deposition (LDED) method were investigated in the production of SS316L-IN625 functionally graded materials (FGMs). In the first scanning strategy, the layers were deposited in one direction (X-X), while they were deposited perpendicular to each other (X–Y) in the second scanning strategy. Functionally graded bulk samples with dimensions of 10 × 42 mm² were deposited in five layers on a 4130 steel substrate using the LDED process. The percentages of IN625 and SS316L in each layer were different to create a graded material. The effects of scanning strategies on the height, standard deviation of height, microstructure, surface roughness, and microhardness of the FGM bulk samples were investigated. The results revealed that the X–Y scanning strategy sample had a better surface quality, a lower height, a lower standard deviation of height, and fewer microstructural defects. Optical microscopy and scanning electron microscopy images evidenced that the bulk samples have columnar and equiaxed dendritic structures. The surface roughness (Ra) of the sample using the X–Y scanning strategy was 84 μm. The Ra of the sample fabricated using the X-X scanning strategy was 120 μm. Additionally, the microhardness value varied between 270 and 410 HV at different points of the bulk samples and decreased as the distance from the substrate increased along the build direction of the FGM bulk samples.