Laser-assisted burnishing of metals

Burnishing has been widely used to produce excellent surface finish, work hardening and compressive residual stress by plastically deforming the workpiece surface layer. However, conventional burnishing is difficult on hard materials, because an excessive burnishing force might be required. A new hybrid burnishing process, laser-assisted burnishing (LAB), is proposed and investigated experimentally in the present study. During LAB, the workpiece surface layer is temporarily and locally softened by a controllable laser beam, and then immediately processed by a conventional burnishing tool. LAB and conventional burnishing experiments were conducted on MP35N, annealed and hardened AISI 4140, respectively, to evaluate the effect of laser power on the burnishing results. Because more plastic deformation occurs in LAB than in conventional burnishing, thanks to the temporary softening of workpiece material prior to burnishing, it is shown by these experiments that LAB can produce much better surface finish, higher surface hardness and similar compressive residual stress compared to its conventional counterpart.