Experimental investigation of surface roughness reduction of biomaterial (Co-Cr-Mo) alloys using MFAFP and RSM-based optimization

Abstract

Precision machining for medical and aeronautical high-performance components relies on the surface quality (SQ). Surface finish issues can cause malfunctions, premature wear, and dimensional errors. The magnetic field-assisted finishing process (MFAFP) was used to refine nano-surfaces to overcome these issues. Cobalt-chromium-molybdenum (Co-Cr-Mo) alloys are popular workpiece materials for orthopedics implants owing to their strength and wear resistance. Carbonyl iron particles (CIPs), diamond abrasive particles, and paraffin-grease oil comprise the magnetorheological fluid (MRF) of the MFAFP. A CNC-controlled spinning tool aligned the chains of CIPs and regulated surface polishing using magnetic forces. The novelty is that the study optimized the tool rotational speed, workpiece-tool gap, and finishing time using Response Surface Methodology (RSM) based on a central composite design (CCD) for superfinishing of (Co-Cr-Mo) alloys by MFAF processes. An optical profilometer measured surface roughness (R_a) for in-process evaluation. Scanning electron microscopy (SEM) topography and atomic force microscopy (AFM) morphological images were used to confirm the nano-scale-SQ. The optimized technique red uced the R_a from 450 to 70 nm, resulting in an experimental improvement (%∆Ra) of 84.5%. The RSM model projected %∆Ra as 80.135%, whereas the confirmatory experiment obtained 81.7%, resulting in a low prediction error of 1.92%, proving the robustness and accuracy of the model.