Definition - What does Burnishing mean?
Burnishing is a surface treatment performed on steel alloys to prevent stress corrosion cracking. It is a solution to reduce tensile residual stress in a material that has undergone welding or machining by providing an austenitic compressive residual stress to create a balance of residual forces. It aims to reduce the surface and near-surface residual stresses.
Burnishing is a corrosion prevention technique that provides a long-lasting end product, a mirror surface finish and improved mechanical properties in one pass.
Burnishing is used in the aerospace, military, and nuclear power industries to enhance surface treatment and corrosion prevention on welded and machined parts.
Corrosionpedia explains Burnishing
When a metal undergoes cold working and fabrication that applies tensile stress over the material's threshold limit, there is an increased probability of stress corrosion cracking due to the specific properties of the alloy and the environment. These residual forces occur at the surface or near surface of these base metals.
Ball and roller burnish tools smooth and harden a substrate's surface. Hardening provides the compression forces necessary to create the stability of residual forces inside the finished material.
The type of finish will depend on the depth, pressure and the speed of the burnish tool. The residual compression is achieved when the peaks on the surface of a machined material flows into the valleys of the material by plastic deformation, thus creating a shiny finish.