Effect of Build Angle on Surface Roughness of High-speed Selective Laser Melted Ti–6Al–4V Alloy

Abstract

Despite recent progress in achieving high mechanical properties of metal additive manufacturing, the low productivity represented by slow manufacturing speeds still remains a bottleneck of the technology. We improved the scanning speed of selective laser melting (SLM) with Ti-6Al-4V up to 1800 mm/s for high printing speed with affordable mechanical properties. In addition, the hot isostatic pressing (HIP) process was applied as post-treatment process to remove porosity of the high-speed printed SLM specimens. However, the HIP process caused a microstructural change from α′-lath martensite to a Widmanstӓtten α-lamellar structure. This microstructural change was most pronounced on the surface area and caused inter-lamellar fracture. Here, we investigate this phenomenon with microstructural and computational analysis. The results indicate that this deterioration phenomenon is highly dependent on surface roughness, which can be controlled with a build angle set-up.