Abrasive polishing load effect on surface roughness and material removal rate of Al2O3, ZTA and SiC

Abstract

The surface quality determines the performance of ceramic tribological components, e.g., bearings and seals. Surface conditioning processes, like polishing, are generally responsible for the largest portion of the manufacturing costs of these components. Therefore, process parameters, such as polishing load, should be optimized for economic reasons. Sintered alumina (Al2O3), zirconia-toughened alumina (ZTA) and silicon carbide (SiC) samples were polished in a sequential two-step process using a water-based diamond abrasive slurry with particle sizes of 3 μm (P1) and 1 μm (P2) on woven and nap cloths, respectively. The effect of material and polishing load (40, 50 and 60 N) on 2D roughness parameters (Ra, RSm, Rz and Rsk) and material removal rate (MRR) were evaluated by a MANCOVA statistically designed experiment. Polishing steps reduced Ra and Rz in succession, with the greatest absolute reduction occurring at P1. Load and material affected only MRR and RSm, when controlled by the effect of initial roughness parameters of surfaces. The low surface porosity fraction combined with very low Ra of surface topography plateaus, especially after P2, resulted in much higher RSm values for SiC. Atomic force microscopy (AFM) images of polished surfaces revealed that, on a finer scale, material removal mechanisms were ductile. MRR for SiC was the highest and proportional to polishing load, while the load did not affect it for the oxide ceramics. The synergy between the mechanical action of abrasives and tribochemistry between SiC and water explains its higher MRR and better surface finish, while Al2O3 and ZTA relied mainly on the ductile mechanisms to improve their surface quality.