Experimental investigation of surface roughness and microstructure characterization of the SLM printed parts

Additive manufacturing or layer-by-layer manufacturing has been effectively applied in the manufacture of parts with complex shapes. Selective laser melting (SLM) is an additive manufacturing method that uses lasers to melt metal powder when forming printed layers. The quality of products printed by SLM is an issue of concern to users. Product quality is evaluated through criteria such as dimensional accuracy, surface quality, and physical and mechanical properties to ensure the working requirements of the part. The quality of printed products is affected by many factors such as material properties, powder size, and printing parameters. In this study, the surface roughness and microstructural characteristics of printed products were experimentally studied in considering the influence of printing parameters by the SLM printing method when printing Ti6Al4V metal powder. The material has an average particle size of 43 µm. The influence of the printing parameters including laser power, printing layer thickness, printing speed on surface roughness and microstructural characteristics was evaluated. The range of values of the above three parameters includes laser power from 150 to 350 W, printing speed from 400 to 1500 mm/s, and printing layer thickness from 0.03 to 0.06 mm. The design of experiments method was applied to establish a regression model showing the relationship between surface roughness and printing parameters. In this research, the Ra value achieved ranges from 3.319 to 24.025 µm. The printing parameters ensuring a small Ra value or a smoother printed product surface also lead to good microstructural characteristics, reducing defects such as holes and cracks inside the printed parts