Machine Hammer Peening – A Substitute for Polishing of Pressing Die Surfaces?

Paper i proceeding, 2009

Machine Hammer Peening (MHP) is a new method for finishing of surfaces. With this method the workpiece surface is hammered with a spherical carbide tool. The main objective of the study was to evaluate whether the MHP method could be used as a plausible substitute for manual polishing in pressing die manufacturing. To do this, sample surfaces were hammered and evaluated. Changes to the surfaces were assessed using surface roughness measurements, hardness measurements and optical images. First of all, the workpiece surface was smoothened. Secondly, the surface hardness was increased significantly. Thirdly, the nodules on the workpiece surface were effected. They appeared to be smaller and not as visible. It is probable that they had been plastically deformed and that some of the graphite in the nodules was replaced by material from the surrounding steel matrix. By replacing the graphite in the larger nodule cavities by surrounding steel material, a die surface is created which would be less prone to galling. In addition, with MHP, the amount of polishing needed to manufacture a die surface can be reduced because of the smoothening effect.