B. Podgornik, University of Ljubljana, Ljubljana, Slovenia; S. Hogmark, Uppsala University, Uppsala, Sweden
The aim of the present work was to investigate and compare different surface engineering techniques in terms of galling properties when applied on forming tools. The surface modification techniques included were different grades of polishing, plasma nitriding and DLC coating, all applied to cold work tool steel, respectively. Tribological evaluation against austenitic stainless steel was carried out in a load-scanning test rig, with the load being in the range between 1 GPa and 3.5 GPa. It is concluded that the galling tendency can be greatly reduced by proper polishing of the tool surface. However, selection of a carbon-based multilayer WC/C coating leads to substantially reduced probability of work material transfer even at a relatively high surface roughness, and also under starved lubrication. A combination of nitriding, surface polishing and DLC coating is suggested as the optimum surface treatment of tools aimed at forming austenitic stainless steel.
Summary: Galling tendency of forming tool steel can be greatly reduced by proper polishing of the surface, while selection of a carbon-based coatings leads to substantially reduced probability of work material transfer even at a relatively high surface roughness.
