Preparation and performance investigation of Pore-Confined Free Abrasive Polishing Disc based on water-soluble shell Diamond@Na2SO4 core-shell abrasives

Proposes a novel machining method based on the PC-FAPD. • PC-FAPD combines the advantages of fixed and free abrasives. • Reveals the material removal mechanism of PC-FAPD. To simultaneously enhance the surface polishing quality of workpieces and reduce processing costs, this study proposes a fabrication method for Pore-Confined Free Abrasive Polishing Disc (PC-FAPD) using water-soluble shell Diamond@Na 2 SO 4 core-shell abrasives. During polishing, the Na 2 SO 4 shell dissolves to form pore-confined free abrasives, which act in a three-body friction mode under pore constraints to enable high-efficiency, high-quality polishing while ensuring high abrasive utilization. Diamond@Na 2 SO 4 core-shell abrasives were synthesized via evaporative crystallization, and the influence of different Diamond/Na 2 SO 4 mass ratios on coating thickness was systematically investigated, followed by an evaluation of the polishing performance of PC-FAPD with core-shell abrasives of varying coating thicknesses. Results show that as the Diamond/Na 2 SO 4 mass ratio decreases, the Na 2 SO 4 coating becomes thicker and denser; at a 1:3 mass ratio, the C atomic percentage in the abrasives drops from 92.690% to 12.628%, the particle size increases from 4.3 μm to 6.3 μm, and the diamond coating thickness reaches 1 μm. Polishing tests on single-crystal SiC indicate that the uncoated abrasive disc achieves the highest material removal rate (MRR) of 2968.06 nm/h, while the 1 μm-thick coating disc yields the lowest surface roughness (Sa = 1.31 nm). As the coating thickness of the core-shell abrasives increases, the material removal mode of the abrasives on the workpiece becomes closer to that of free abrasives. This reduces the MRR to a certain extent but enables better surface quality, with the performance of repeated polishing remaining relatively stable. Friction and wear experiments confirm that thicker coatings transition the removal mode from two-body plowing to three-body rolling and scratching. This research provides a novel strategy for ultra-precision machining.