Three dimensional surface topography characterization of the electron beam melted Ti6Al4V

Abstract

The properties of the components fabricated via electron beam melting (EBM) are known to be affected by different processing parameters such as beam current, offset focus, scan speed, layer thickness, powder size and part orientation. This clearly has part design, placement and performance implications and therefore in this study, the effect of part orientation on the surface topography of the EBM Ti6Al4V alloy was investigated. Three different surface finishes were obtained by fabricating disc components in the horizontal (0°), inclined (55°) and vertical (90°) in the EBM build chamber. Their resulting amplitude surface topographies were characterized through white light interferometry and scanning electron microscopy. Comparison of the results revealed a significant difference in numerical values of the 3-D surface roughness parameters. For the average roughness, the horizontal (0°) surface had a smoother surface (Sa = 15.8 μm) whereas the inclined (55°) and vertical (90°) surfaces had rougher surface characteristics with and Sa = 36.8 μm and 54.3 μm respectively. The results showed that part orientation of titanium during EBM can produce surfaces with different characteristics due the anisotropic melting of the powders by the EBM process leading to part design considerations and complexities associated with EBM parts. The selection of the 3-D surface topography parameters and surface morphology characterization were also shown to address the inadequacies of two-dimensional (2-D) surface analysis.