BURNISHING AS A SURFACE TREATMENT PROCESS: A REVIEW

The service life of machined components depends upon the surface and subsurface properties which are influenced by different manufacturing processes. Conventional surfaces finishing techniques like grinding, lapping, honing etc. are used to reduce the surface roughness on machined surfaces and also to improve the aesthetics. All these methods essentially depend on material removal in the form of chips to attain the desired surface finish. The chips thus removed may cause surface abrasion resulting in geometric tolerance deviations. Burnishing is essentially a chip-less, post-machining process in which the metallic components after machining could be finished to deform surface irregularities to fill valleys. It uses a hard ball or roller with high surface finish, sliding against the work piece and pressure greater than yield strength of work material is applied at the contact area resulting in plastic deformation. This plastic deformation at the surface has many advantages apart from improvement in surface texture. The process of burnishing can be applied not only to soft and ductile materials but also very hard metals and on different surface geometries like cylindrical, tapered, flat etc.