Effect of Selective Laser Melting Parameters on the Melt Pool Formed by Single Tracks of the Heat-Resistant Inconel 718 Nickel Alloy

Abstract

The characteristics of single-track melt pools, such as size, shape, and stability, formed by the heatresistant Inconel 718 nickel alloy powder subjected to selective laser melting (SLM) were studied. The objective was to determine the range of optimal SLM parameters to provide a stable track with a depth of two to three layers. Single tracks were built using various combinations of process parameters: laser power from 50 to 400 W with a step of 30 W and scanning speed from 450 to 1000 mm/sec with a step of 50 mm/sec (144 modes in total). An Axiovert 200M MAT light microscope (Carl Zeiss) was employed to examine the cross sections of single tracks and evaluate the geometrical parameters of the melt pools. Features pertaining to the effect of the scanning speed and laser power on single-track depth and width and their ratio were experimentally studied. An unstable track formed at low power (P = 50 W) and low scanning speed (V = 450–500 mm/sec), while no track appeared at all at higher speeds. A stable track formed at power P = 80–200 W at low speeds (V = 500–900 mm/sec) and became unstable and intermittent when speed increased to V = 1000 mm/sec. With higher laser power (P = 230–400 W) and low process speeds, a continuous track formed but had an increased variable width, being indicative of a deviation from the stable track formation conditions. It was first established that the intensity of the scanning speed effect (450–1000 mm/sec) on the single track depth varies by more than 2.5 times depending on the laser power (50–400 W). The process parameters that would ensure the formation of an optimal single track in terms of geometric parameters were determined.