Due to the layer-based nature of the powder bed fusion (PBF) process, part surfaces oriented in space at varying angles with respect to the build direction are differently affected by a wide array of manufacturing-induced phenomena (staircase effects, spatter, particles, etc.), which can significantly influence the functional behaviour of such surfaces, and choices for post-processing where needed. For assessing surface topography of PBF surfaces most researchers have looked at surface texture parameters (profile - ISO 4287 and areal - ISO 25178−2). Texture parameters provide useful summaries of surface-wide properties, but do not allow the analysis to focus on specific topographic formations of interest. On the contrary, feature-based characterisation encompasses a series of recently introduced methods that allow to isolate and characterise specific topographic formations of interest starting from topography datasets acquired with conventional areal topography measurement solutions. In this work, the topography of electron beam powder bed fusion (EBPBF) surfaces as a function of orientation with respect to the build direction was investigated using a combined approach consisting of both texture parameters and feature-based characterisation. A custom-designed test part featuring surfaces at different orientations was measured with a focus variation instrument. A feature-based characterisation pipeline was implemented for the identification, isolation and geometrical characterisation of spatter formations and particles present on the as-built surfaces. The surfaces deprived of the identified features were then characterised by means of conventional ISO 25178−2 texture parameters. The results confirm that combining feature-based characterisation with conventional analysis through texture parameters creates new perspectives for looking at EBPBF surfaces, thus better supporting future research endeavours aimed at achieving a more comprehensive insight on the nature of EBPBF surfaces. For the first time quantitative results are provided on number, shape and localisation of spatter and other particles in EBPBF surfaces as a function of build orientation, and texture parameters are provided that describe the fabricated surfaces in a more reliable way as particles and spatter formations have been removed.
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