Analysis of surface roughness and hardness in ball burnishing of titanium alloy

Ball burnishing is a popular post-machining metal finishing operation. An attempt has been made in this paper to optimize the process parameters during burnishing of titanium alloy (Ti-6Al-4V). Ball burnishing process parameters such as burnishing speed, burnishing feed, burnishing force and number of passes were considered to minimize the surface roughness and maximize the hardness. The lubricated ball burnishing experiments were planned as per L₂₅ orthogonal array and signal to noise (S/N) ratio was applied to measure the proposed performance characteristics. The validation tests with the optimal levels of parameters were performed to illustrate the effectiveness of Taguchi optimization. The optimization results revealed that burnishing feed and burnishing speed are the significant parameters for minimizing the surface roughness, whereas burnishing force and number of passes play important roles in maximizing the hardness. The optimization results showed greater improvements in surface finish (77%) and hardness (17%) when compared to pre-machined surfaces.