Improved metallurgical properties
Burnishing cold works the metal of a machined part. Tool marks are rolled out. Grain structure is condensed and refined, and the compacted surface is smoother, harder and longer wearing than ground or honed surfaces. The rolling action also greatly reduces surface porosity and scratches which could hold reactive substances or contaminants. As a result, the corrosion resistance of burnished surfaces is higher than the open surfaces produced by grinding or honing. Depending on the type of material being burnished, surface hardness can be increased by as much as 10 points Rockwell C.
This increase often eliminates the need for heat treating of surface treatment as a means of improving wear resistance. Another metallurgical improvement stems from induced residual compressive stresses in the surface of the part as a result of plastic deformation in the roller burnishing operation. These compressive stresses greatly increase the strength properties and fatigue life of the part, because any forces on the part must overcome these residual stresses, as well as the tensile strength of the materials, before fatigue conditions occur.
Improved surface finish
Roller burnishing imparts a high finish to any machinable metal. Surfaces that are bored, reamed or turned to 125 micro inches or more can be finished to 4 micro inch CLA or less in one pass at feed rates of 125 to 300 mm/min.Roller burnishing replaces grinding, honing, lapping and other expensive secondary operations.