Experimental and response surface study on additive manufacturing of functionally graded steel-inconel wall using direct laser metal deposition

In the present study, the effective parameters in the Direct Laser Metal Deposition Method (DLMD) of SS316L-Inconel 625 grade material were investigated. A 1000 W continuous-wave fiber laser was used to manufacture a five-layered gradient wall. The weight percentages of Inconel 625 and SS316L were different in each layer. Response Surface Methodology (RSM) was used to study the effects of scanning speed and laser power -each in three levels- on the average width, surface roughness, average microhardness, standard deviation of the width, and standard deviation of the height of the gradient walls. Also, the microstructure of the gradient walls was investigated using SEM images and EDS analysis. The results showed that the average width and surface roughness of the walls would increase by decreasing the scanning speed and increasing the laser power. The increase in the scanning speed and decrease in the laser power decreased the standard deviation of the width and the height of the walls. The lowest surface roughness of 96 µm was obtained at the highest scanning speed of 200 mm/min while the lowest values of the standard deviation of the width and standard deviation of height were 76 and 70 μm, respectively at this speed. It was also found that the microhardness value increased significantly with the increase in the scanning speed due to the higher solidification rate.