Optimization of ball-burnishing process parameters on surface roughness, micro hardness of Mg-Zn-Ca alloy and investigation of corrosion behavior

In this work, optimization of ball burnishing parameters (depth of press, feed, burnishing force, number of passes) and their effect on surface roughness, microhardness and corrosion behavior of Mg-4%Zn-1%Ca alloy is investigated. The Taguchi optimization technique was used to determine the number of experiments and by considering S/N ratios, right combination of ball burnishing parameters were selected. Results obtained from the experiments were investigated and it is understood that depth of press, feed and number of passes have a significant effect on surface roughness, microhardness and consequently improves corrosion resistance of Mg-4%Zn-1%Ca alloy. From ball burnishing experiments it is deduced that there is large increase in microhardness of 107 Hv and surface roughness of 129 nm, achieved for the depth of press 0.45 mm, burnishing force 250 N, feed 450 mm min^-1 and number of passes: 2. Corrosion behavior of the alloys were analyzed using potentiodynamic polarization and electrochemical impedance spectroscopy techniques in Hank's balanced salt solution. The lowest corrosion rate was observed in DFN 442 sample (1.43 mm y^-1) which is 4.7 times better than the homogenized alloy (6.73 mm y^-1). It has been found that the ball burnishing plays an important role on surface roughness, microhardness and corrosion behavior of Mg-4%Zn-1%Ca alloy.