Adapted surface properties of hot forging tools using plasma technology for an effective wear reduction

Interacting high mechanical, tribological, chemical and thermal cyclic load components of hot forging processes are process-related and acting geometrically dependent. To enhance the cost effectiveness, there is a big interest in reducing the occurring wear which is a result of these complex load regimes during processing. The presented work identifies the different main wear mechanisms in forging dies and the subsequent abstraction in the configuration of different model tests. Thus, an accentuation of the predominant load component was possible in order to develop adapted plasma nitriding processes partially combined with PVD or PEVD hard coatings to reduce effectively the specific wear like plastic deformation, cracking and abrasive or adhesive wear respectively. The change of the primary surface shape of forging tools was found to be essential for the development of the wear progress. This was described by using the Abbott-Firestone graph finding the core roughness S-k to be a suitable describing parameter. Thus, conditioning methods like abrasive finishing or severe shot peening represent tool enhancements for a further wear reduction. The definition of distinct tool topographies in addition with a stabilization of the initial state of the tool surface achieved with hard coatings and/or additional diffusion treatment is a very promising approach to enhance the wear resistance of forming tools. (C) 2015 Elsevier B.V. All rights reserved.