Abrasive flow machining of laser powder bed fusion fabricated mini-channels: Modelling and verification

Abstract

Abrasive flow machining (AFM) is efficient in polishing large channels while it faces challenges in post-processing mini-channels (diameters from 1 to 2 mm) fabricated by Laser-Powder Bed Fusion (L-PBF) due to an unpredictive material removal in the mini-channels. This paper aims to develop an accurate material removal model for L-PBF mini-channels accounting for an inhomogeneous channel profile. Ti6Al4V channels with a 2 mm diameter were fabricated using L-PBF. The surface topography of the mini-channels' inner wall, including circularity and surface roughness, was characterized using a micro-CT to study its evolution during the AFM process. An AFM model accounting for surface features of L-PBF fabricated mini-channels was developed, including transient erosion wear and steady-state abrasive wear. Results indicate that the material removal rate of the top region with high surface roughness is significantly high in the first 46 cycles of AFM, with nearly 79 % of the total material removal occurring in this period. During this time, the surface roughness S_a reduces to a saturation value of approximately 2.5 μm. The proposed model predicts surface topography evolution during the AFM process, with an average deviation in material removal of 8 μm (relative deviation 5.29 %), after reaching a steady state at 46 cycles. Such a tool provides engineers with a reference for minimal material removal and optimized processing time.