Selective Laser Melting of Titanium Alloys: Simulation of Scanning Speed Effects with High Layer Thickness

The Selective Laser Melting (SLM) process involves directing a laser beam onto a powder bed to create intricate metal parts. However, the as-built quality is strongly influenced by several process parameters, especially, laser power, scanning speed, layer thickness, and hatch spacing. Therefore, this study explored the impact of varying scanning speed (800 to 1,400 mm/s) on the temperature distribution and morphology of the melt pool using Ti-6Al-4V material with a high layer thickness of 80 μm and constant laser power of 170 W using numerical simulation. The temperature distribution, assessed from the top view and at the cross-sectional plane, showed that a lower scanning speed (v) or higher Linear Energy Density (LED) results in a wider hot zone. The effect of scanning speed on melt pool morphology and dimensions is demonstrated through the classification of molten pools based on the width-to-depth ratio of the melt track. The higher scanning speeds resulted in a transition mode, while low scanning speeds led to the formation of a keyhole mode. The findings indicate that under these specified conditions of laser power and powder layer thickness for Ti-6Al-4V, a scanning speed of 1000 mm/s is optimal, as it produces a weld with a w/d ratio that avoids the problematic keyhole mode while maintaining good weld morphology and quality.