Optimization of Finishing Consistency in Abrasive Water Flow Polishing of IN718 Superalloy Inclined Hole Array Based on Fluid Dynamic Pressure Distribution

ABSTRACT

Small‐to‐micro‐sized inclined hole array are key geometric features in turbine blades of aero engine. In abrasive water flow finishing of such hole arrays, nonuniform dynamic fluid pressure distribution across hole walls lead to inconsistent finishing results. To address this problem, a novel method is proposed in this study for improving finishing consistency across the inclined holes by determining the appropriate processing parameters based on fluid dynamic pressure distribution. In the first stage, the correlation between fluid dynamic pressure and polishing results, that is, material removal and surface roughness, on the hole wall has been theoretically and experimentally investigated. Then, prediction models have been developed to establish a relationship between fluid dynamic pressure and polishing results via limited simple experiments in vertical holes. Afterward, it has been extended to optimize the machining time for inclined hole arrays to minimize the deviation in inter‐hole finishing results of inclined hole arrays using calculated dynamic pressure distribution on the hole wall. Model validation showed that the relative deviations of surface roughness and material removal from their target values were within 13%. The average Ra was reduced from pre‐polishing 5.2 μm to post‐polishing 1.45 μm, that is, a decline of 72.12%, and the Ra deviations among holes were controlled within ± 12%. This research shows that the proposed method can effectively improve finishing consistency of inclined hole array and can be extended to polish cooling holes of turbine blade.