Rheological characterization of process parameters influence on surface quality of Ti-6Al-4V parts manufactured by selective laser melting

Additive manufacturing is one of the promising production processes, which has the ability to manufacture final shape directly from computer-aided designs. In this research, the thermal effect of process parameters on the average surface of selective laser melting (SLM) Ti-6Al-4V is discussed and mathematically characterized. Based on Taguchi L25, the experiment was designed, and laser power, scan speed, hatch spacing, laser increment pattern angle, and heat treatment in five levels were selected as input parameters. Interfacial forces including surface tension, Marangoni’s effect, pressure in droplet, capillarity force, work adhesion, wetting, recoil pressure, drag forces (due to solid-liquid transition) and interaction of surface tension, hydrostatic and vapor pressures have been characterized mathematically to analyze their effect on surface quality. Results showed higher energy density and temperature cause lower surface tension and capillary force, generating unstable and lower surface quality. In addition, higher energy density and temperature increase droplet pressure, internal pressure, recoil pressure, and thermal stress and change the balance of forces on the surface of the melting pool and reduce surface quality.