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E. Kozeschnik, B. Adjassoho, C. Lechner, Ch. Habersohn, F. Bleicher, S. Gössinger, C. Bauer:
"Controlled Surface Treatment With Machine Hammer Peening";
Talk: 22nd International Conference on Metallurgy and Materials, Brno, Tschechien; 05-15-2012 - 05-17-2012; in: "METAL 2013", (2012), Paper ID B28, 6 pages.

Abstract
Machine Hammer Peening (MHP) it is a cold deformation process with the aim of improving the upper surface layer of metal work pieces. The process is carried out by an actuator, which can be mounted on conventional machining tools. A vertical guide, oscillating plunger, with a spherical carbide tool can perform well-directed hits on the work piece surface. The authors of this paper have investigated the effect of MHP on the materials microstructure and the mechanical characteristics of different machine hammer peened work pieces. The microstructure of the tool steel X3CrNiMo13 4 (martensitic - austenitic structure) was investigated in peening direction, normal to it as well as perpendicular to it. Also, nano-hardness measurements on X3CrNiMo13 4 were done, to see if the MHP process has a significant influence on the results of the hardness measurements. Because of the fact that MHP creates a "valley and hill" like morphology in the range of some µm on the surface, the question arises whether there is a significant difference between the hardness measured in the valley or on the hill. The second mechanical characteristics, which can be influenced by the MHP process, is the induction of residual stress. Therefore, measurements with the hole drilling method on the material X3CrNiMo13 4 were done to see how compressive residual stress can be induced by MHP.

Metallography, Surface hardness, residual stress;