Experimental investigation of surface integrity improvement using a novel magnetorheological finishing tool setup

Magnetorheological finishing is an advanced process of precision finishing used to achieve an outstanding surface quality, through the use of the magnetic field-assisted abrasive polishing. In the present study, a new permanent magnet-based magnetorheological finishing tool has been designed, fabricated and used to finishing cylindrical mild steel workpieces. A developed apparatus based on conventional lathe with this new design configuration has been assembled with magnetorheological fluid containing carbonyl iron powder and silicon carbide abrasive mixed in grease-paraffin oil as a carrier media and experiments have been performed to find the effect of process parameters like rotating speed, abrasive concentration, magnetic field-assisted polishing action and time of finishing on surface roughness, surface morphology and micro-hardness to compare magnetorheological finishing process with manual finish with respect to the finishing of workpiece. Experimental results have showed the best quality of the surface after the magnetorheological finishing polishing. The value of the average surface roughness (Ra) for grinded mild steel has been obtained as 1.727 µm, which has been reduced to 1.113 µm after 90 minutes and then 1.050 µm after 120 minutes which comes to about 39.2% improvement over manually finished with magnetorheological finishing. Scanning electron micrographs for manually finished as well as magnetorheological finishing-finished surfaces have been taken and it showed that the asperities, grooves and scratches were removed from the surface of the workpiece. Micro-hardness value increased from 140 to 156 HV.