Direct Laser Metal Deposition (DLMD) is a state-of-the-art manufacturing technology used to fabricate 316L stainless steel/Inconel 625 functionally graded material (FGMs) in this research. For the practical application of these materials in the industry, the effects of process parameters on the geometric characteristics and surface roughness require more investigation. This FGM was additively manufactured in five layers by changing the 316L stainless steel/Inconel 625 ratio in each layer. The effects of laser power on geometric characteristics, height stability, and surface roughness were investigated. The microstructural analysis and microhardness profiles were studied. The results show that despite the high solidification rate, the segregation of alloying elements into dendritic areas occurred. It was also found that increasing the laser power will increase the height, width, height stability, and surface roughness of the gradient walls. The maximum width and height of the deposited layers were 1.615 and 6.42 mm, respectively, at the highest laser power (280 W). At the laser power of 220 W, the least surface roughness (R_a = 105 µm) and the best height stability (0.461 mm) will be obtained. The microhardness values will differ in various sections of the gradient walls in a range of 225–277 HV.

The melt-pool behaviors during selective laser melting (SLM) of Al₂O₃-reinforced and a eutectic mixture of Al₂O₃-ZrO₂-reinforced AISI 304 stainless-steel composites were numerically analyzed and experimentally validated. The thermal analysis results show that the geometry of the melt pool is significantly dependent on reinforcing particles, owing to the variations in the melting point and the thermal conductivity of the powder mixture. With the use of a eutectic mixture of Al₂O₃-ZrO₂ instead of an Al₂O₃ reinforcing particle, the maximum temperature of the melt pool was increased. Meanwhile, a negligible corresponding relationship was observed between the cooling rate of both reinforcements. Therefore, it was identified that the liquid lifetime of the melt pool has the effect on the melting behavior, rather than the cooling rate, and the liquid lifetime increases with the eutectic ratio of Al₂O₃-ZrO₂ reinforcement. The temperature gradient at the top surface reduces with the use of an Al₂O₃-ZrO₂ reinforcement particle due to the wider melt pool. Inversely, the temperature gradient in the thickness direction increases with the use of an Al₂O₃-ZrO₂ reinforcement particle. The results of melt-pool behaviors will provide a deep understanding of the effect of reinforcing particles on the dimensional accuracies and properties of fabricated AISI 304 stainless-steel composites.