Abstract：IN718 alloy is of great interest currently, due to its extraordinarily excellent strength, corrosion resistance,
and fatigue properties, which is the main material for manufacturing aero-engines with complex structures.
As one of the most reliable and feasible additive manufacturing technologies, selective laser melting (SLM) can
greatly shorten the manufacturing cycle and improve the utilization of materials. However, defects such as
spheroidization, porosity and cracks often occur in the SLM process, reducing the quality of the SLMed parts. To
improve the quality of SLMed parts, the effects of process parameters such as laser power, scanning speed and
hatching space on the quality indexes of the SLMed parts and the sensitivity analysis of each process parameter
were studied. The SLM process parameters of IN718 alloy were optimized. This paper conducted multi-groups of
experiments with different laser powers, scanning speeds and hatch spacings, measuring the surface roughness,
surface height difference, sphericity, surface melting width, microhardness and microstructure of the SLMed
parts. Analysis of extreme differences was employed to process the data obtained to investigate the sensitivity of
the process parameters to the above factors. When the laser power is 180 W, the scanning speed is 800 mm/s, and
the hatching space is 0.10 mm, the SLMed part with the surface roughness of 32 μm and the sphericity of
3.623% are obtained. While with a laser power of 160 W, a scanning speed of 600 mm/s and a hatch spacing of
0.06 mm, the surface roughness increases to 177 μm and the sphericity decreases to 1.007%. Irregular pores are
observed in the microstructures of the SLMed parts with a laser energy density of 32 J/mm3, while spherical
pores are observed in the microstructures of the SLMed parts with a laser energy density of 83 J/mm3. Among the
preset process parameters, for the surface roughness and the sphericity, the influence of scanning speed is the greatest, followed by laser power, and the influence of lap spacing is the least. Microhardness increasing and then
decreasing along the build direction, shows a trend similar to a normal distribution. Irregular pores occur in the
molten pool at low laser energy densities, while spherical pores occur at high laser energy densities, and almost
no obvious defects inside the molten pool at moderate laser energy densities. This study could help to improve
the surface quality of selective laser melting parts of IN718 alloy by optimizing the process parameters.
2023, Vol. 33 
