Halbach-enhanced magnetorheological polishing of SUS304 using core–shell diamond abrasives

Magnetorheological polishing (MRP) is a promising ultra-precision finishing technology for advanced engineering materials, but its performance is constrained by inefficient magnetic-field utilization and unstable abrasive–surface interactions. This study proposes a field-engineered MRP strategy integrating a dual-layer Halbach magnetic architecture with mechanically reinforced Ni–P-coated diamond–carbonyl iron core–shell abrasives (CIP@Ni–P/Diamond). The Halbach structure concentrates magnetic flux in the polishing zone, while the core–shell abrasives enhance abrasive retention, chain stability, and load transfer. Molecular dynamics simulations reveal that moderate magnetic loading promotes stable abrasive engagement, uniform material displacement, and reduced pile-up, whereas excessive loading intensifies subsurface deformation and unstable material flow. Experimental validation on SUS304 stainless steel demonstrates that the optimized process reduces surface roughness (Ra) from approximately 500 nm to 6 nm, with improved surface uniformity and suppressed waviness. The proposed strategy provides an effective route for controllable material removal and ultra-precision finishing of complex engineering surfaces.