Investigation of the Effect of Surface Burnishing on Stress Condition and Hardening Phenomena

The purpose of this paper is to present a comprehensive study of the stress state and hardening characteristics of low-alloyed aluminium cylindrical specimens subjected to the diamond burnishing process. Diamond burnishing has a surface hardening effect on structural steels. In the present study, our aim was to check whether this surface hardening effect is also observed for other (less hard) material grades, such as low-alloy aluminium. We also aimed to determine the technological parameters at which the greatest relative increase in hardness can be achieved by burnishing. In addition to the hardness test, the changes in the residual stress state due to burnishing were also analysed. Both hardness and residual stress tests were performed in two variants. Of the 4 technological parameters (burnishing speed, feed, burnishing force and number of passes), the burnishing speed was set to constant for one variant and number of passes was set to constant at the other variant, while two levels were chosen for the other parameters. A special formula was developed to determine the relative improvement in residual stress and hardness. Our experiments were performed using a full factorial experimental design. The results show that diamond burnishing has surface hardening effect and increases of residual stress on an aluminium alloy when applying adequate technological parameters.