Evolution of Surface Roughness of Wrought and Additively Manufactured Inconel 718 During Centrifugal Disc Finishing

Surface finishing is a crucial post-processing step for performance-critical parts resulting from additive manufacturing (AM). Mass finishing technologies like centrifugal disc finishing (CDF) are garnering interest for their ability to process multiple parts simultaneously and no requirement of geometry-specific fixturing. Nonetheless, such processes are challenging to control and optimize partly because of their stochastic mechanics. The overarching goal of this study is to understand the mechanics of surface finishing by CDF of wrought and AM Inconel 718 (IN718) alloy. This study presents the effect of changes to two independent control variables of CDF, the size/shape of finishing media, and the process duration. To understand the effect of duration on mechanics of finishing, the evolution of the finishing media used is also modeled in harmony with the evolution of the surface roughness of our IN718 parts. From this information, a mechanism of evolution of surface roughness in IN718 and the finishing media is proposed and phenomenologically formulated. Our findings suggest that: (1) the mechanism of surface finishing transitions from cutting to plowing after a certain process duration determined by characteristics of the part being finished and (2) media shape/size plays a significant role in the evolution of roughness textures of specific Fourier wavelengths.