Definition - What does Burnish mean?
This is a surface treatment done on steel alloys to prevent the effect of stress-corrosion cracking. It is a solution to curb tensile residual stress in a material that has undergone welding and 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.
It is used in the aerospace industry, military industry and the nuclear industry to enhance surface treatment and corrosion prevention on welded and machine parts.
Corrosionpedia explains Burnish
When a metal undergoes cold working and fabrication that include the application of tensile stress over the material threshold limit, there is a greater chance that the combination of the properties of the alloy and the environment may lead to stress-corrosion cracking. These residual forces occur at the surfaces or near surfaces of these based metals.
Ball or roller burnish tools are used to smoothen and harden the surface of a substrate. The effect of hardening provides the necessary compressive forces 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 setting. 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.
Burnish as a corrosion prevention technique provides a long-lasting end product, a mirror surface finish, and improved mechanical properties in one pass.