Surface morphology and dimensional accuracy of additively manufactured Ti-6Al-4V alloy: Effect of variable scanning speed with constant laser power in widespread energy density

Abstract

The present study aims at analysing the combined role of laser power (LP) and scanning speed (SS) on the surface topography and dimensional accuracy of Titanium (Ti–6Al–4V) alloy fabricated through a laser-based powder bed fusion process. The widespread volumetric energy densities (VEDs) ranging from 25 J/mm³ (S₁) to 120 J/mm³ (S₁₀) were chosen with five different combinations of LP with varying SS, such as 150 W (276 and 850 mm/s), 250 W (630 and 990 mm/s), 300 W (395 and 465 mm/s), 350 W (405 and 1100 mm/s), and 370 W (850 and 1270 mm/s). Sample S₁ (25 J/mm³) revealed the presence of partially melted track and VED beyond 60 J/mm³ producing a detrimental surface quality due to over-burning. At low LPs of 150 and 250 W, a reduction in SS led to a decrease in surface roughness, owing to sufficient melting of the powder layers. Meanwhile, at high LPs of 300 and 350 W, a reduction in SS caused the burning of the layer which led to an increase in the roughness. In contrast, at a high LP of 370 W, a reduction in SS caused a decrease in the roughness parameters. Both LP and SS were found to have strong interdependence in the achievement of the as-built surface quality. Further, the samples fabricated with excessive VED S₇ (75 J/mm³), S₈ (90 J/mm³), S₉ (105 J/mm³) and S₁₀ (120 J/mm³) caused delamination of layers and resulted in severe angular distortion.