Multiphase hydrodynamic flow finishing for surface integrity enhancement of additive manufactured internal channels

The surface finishing of internal channels for components built using additive manufacturing is a challenge. The resulting surface finish uniformity of additive manufactured internal channels (such as fuel transfer lines and cooling passages) is an issue. Therefore, we propose a novel surface finishing technique using controlled hydrodynamic multiphase flow with abrasion phenomenon to overcome the challenges in the surface finishing of additive manufactured internal channels. In this study, we performed the internal surface finishing on AlSi10Mg components manufactured by direct metal laser sintering. We investigated the surface finish potential of the proposed hydrodynamic cavitation abrasive finishing (HCAF) by varying the process parameters, namely, the hydrodynamic upstream and downstream fluid pressures, fluid temperature, abrasive concentration, and processing time. The HCAF process resulted in greater than 90 % (Ra and Rz) surface finish improvements with an acceptable thickness loss from the internal channels. We precisely mapped the surface morphology transformation at the demarcated zones over the processing time and explained the material removal mechanism. In addition, we analyzed and discussed the surface integrity of the channels in terms of the microstructure, surface hardness, and residual stress. Furthermore, we performed large-area surface topography measurements. Then, we analyzed the resulting areal surface texture parameters to determine the uniformity and flatness of the surface after internal surface finishing. Finally, we discussed the significance of using the proposed HCAF process for complex additive manufactured internal channels.