Influence of shot peening materials on the topography, surface integrity and friction of hot forging tools

Due to a complex load spectrum of mechanical, thermal and tribochemical loads, hot forging tools are subject to increased wear. This results in cost-intensive reworking and possibly unscheduled machine downtimes. To reduce wear, research is currently being carried out on combinations of cooling lubricants and adjusted surface topographies in addition to diffusion and coating treatments. The aim of this contribution is to influence the friction between the workpiece and the tool surface by means of adapted surface topographies including cooling lubricant and thus to reduce tool wear. For this approach, tools were manufactured whose surfaces were treated with different shot peening materials and finally used in cylinder and ring compression tests under forging conditions. In order to draw conclusions on a potential influence of the friction conditions depending on the surface topography, the friction factors with lubricant application were determined with the help of the geometric changes of the ring samples after the forging process. The surfaces were also measured 3-dimensionally and the results from the optical analyses and the friction factor determinations were compared with different shot peening materials. The knowledge gained provides information on the application potential of differently conditioned surfaces in the field of hot bulk metal forming.