Enhancing the corrosion resistance of biodegradable Mg-based alloy by machining-induced surface integrity: influence of machining parameters on surface roughness and hardness

This paper presents the effects of the key machining parameters on surface integrity in terms of surface roughness and hardness in milling, with an aim to increase the corrosion resistance of Mg/Mg-based alloys. With the aid of Taguchi method, experimental plans were designed, in which three parameters-tool rotational speed, federate and depth of cut-were considered. A mathematical model was developed to predict roughness and hardness, followed by a multi-response optimization to determine the optimum parameters maximizing surface integrity. Signal to noise (S/N) ratio and ANOVA analyses show that tool rotational speed has the most significant influence on both roughness and hardness. The optimum parameters obtained via optimization yield a surface roughness R (a) of 0.17 mu m, which is about ninefold reduction from the original roughness (of 1.51 mu m), while the hardness reaches up to 64.78 RHB, which is about twofold increase from as-received surface (of 38.33 RHB). Potentiodynamic corrosion results show that, as compared to as-received surface, machined surface with the optimum parameters exhibits about 9 % increase in corrosion potential and about 54 % decrease in corrosion density and corrosion rate. The results imply that enhanced surface integrity via machining is able to increase the corrosion resistance of Mg alloy implants.