Selective thermally oxidated tool surfaces for dry deep drawing

Friction and wear have significant influence on tool life in sheet metal forming. In this regard, ‎lubricants are generally used to extend the tool life. Since the use of these ‎lubricants does not correspond with the target of sustainable production, methods for ‎dry forming are investigated in the priority program 1676.
Within the scope of this project, the production and the use of tool coatings, which ‎are produced by selective thermal oxidation, are investigated.‎ The oxidative heat treatments of the tool surfaces take place at a defined oxygen residual. Therefore the treatments are carried out under a protective gas atmosphere (nitrogen) and monosilane doped nitrogen, respectively. So it is possible to generate ‎oxide coatings with a defined chemical composition and thickness.‎
The investigation results from the first project period show that oxide layers ‎produced under certain process conditions have friction coefficients, that are ‎comparable to those measured on the tool surfaces after applying lubricants.‎
In the second phase of this subproject, an innovative heat treatment method has been ‎developed. Conventionally, a continuance heating process was used to create the oxide layers. This manufacturing method requires an increased processing time and an increased amount of process gases. In ‎comparison, the new heat treatment method deploys a tube furnace, which ‎allows the production of oxidised-coated specimens with reduced protective gas ‎consumption. ‎In addition, an inductive heating unit was installed in the heating system to decrease ‎process time d. Moreover, various surface modifications were ‎investigated in the second phase of the project including friction and wear ‎experiments. These, and further results from the numerical investigations carried out ‎in the first and second project phases are necessary to understand the approach of ‎dry metal forming researched and thus to ensure the industrial application of this forming ‎technology. This point, applying the gathered experience in ‎dry metal forming in industrial processeswill be the core of the research project in ‎its third phase, whereby a modular deep-drawing tool is going tobe built, which will be ‎equipped with oxidised mold inserts. By manufacturing different components with various geometries using the planned ‎tool system it is possible to increase the load collective on the generated oxide layers ‎successively and thus investigating the behaviour of the layer system in a ‎conventional deep-drawing process.‎ At the same time, the heat treatment process to produce the oxide layers will ‎be continually optimised. Furthermore, the developed numerical model, which was validated on test ‎specimens, will be deployed on the geometries investigated in this phase as well. ‎Finally, the recreating process of the layer system will be investigated, so that more ‎information about the tool life can be determined.‎