Investigation of two MHP process methods and new Actuator design

Abstract

The aim of this research is to gain knowledge about the effects caused by Machine Hammer Peening (MHP) - a mechanical surface treatment process - on the resulting material properties. MHP is based on an oscillating hammer head which strikes repeatedly on a workpiece surface. According to VDI 3416, the technology uses an actuator system to reduce surface roughness, increase surface hardness, and induce near surface compressive residual stresses. Apart from the named surface properties, structured tools can also be applied for surface treatment processes to create defined surface textures. This fact, in combination with the possibility of phase transformation of the crystal lattice of a processed metastable austenitic to martensitic structure by the application of machine hammer peening, contains great potential. Further, to verify the suitability of an investigated piezoelectric actuator to create microstructures, experiments are carried out on the hot work tool steel X38CrMoV5-1 (1.2343), for a subsequent injection molding process which shows hydrophobic surface conditions on a molded plastic part. In addition to surface texturing, the deformation induced phase transformations on a metastable austenitic CrNi material X5CrNi 18-10 (1.4301) is investigated. Due to plastic deformation of the crystalline steel material, as caused by machine hammer peening treatment in the upper layers of the workpiece, phase transformations can be achieved, from a metastable austenitic phase to a martensitic phase.