The project aims at the realization of dry sheet metal forming of aluminum alloys based on a development of surface treatments to optimize the boundary surfaces of tools and metal sheets. During forming processes, certain wear mechanisms cause a rapid tool failure and hinder the utilization of dry forming of aluminum. These mechanisms can be explained by the run-in behavior of carbon based tool coatings and are related to the native passivation of aluminum sheets. Both will be optimized in this project.Amorphous hydrogenated carbon coatings (a-C:H) show very good tribological properties in dry sliding contacts against aluminum. However, the run-in behavior is characterized by a high adhesion tendency and friction values. According to preliminary tests the run-in behavior is a singular and temporarily phase. During the run-in phase the a-C:H coating will be functionalized which leads to a lowered adhesion tendency. As part of this project, surface treatments will be developed for a synthetic functionalization of the a-C:H coating. Therefore, the roughness of the coating will be reduced to few nanometers and the a-C:H growth zone will be removed by plasma polishing of the tool surface and plasma chemical etching of the a-C:H coating. Afterwards the a-C:H boundary surface will be thermally graphitized by Flash Lamp Annealing. These processes are highly material specific. Hence, they will be separately optimized and subsequently combined to a surface treatment process.The natural generated aluminum hydroxide passive layer shows advantageous tribological properties and will be synthesized by a directed homogeneous adjustment of the native passivation layer on the sheet metal surface.Therefore, the existing oxide layer will be replaced by preferably gamma-AlOOH to utilize the anti-frictional properties of gamma-AlOOH within the sheet metal surface. The synthesized passivation layer substitutes the favorable water-lubrication by a well suited sheet metal pre-treatment. The oxide layer will be modified by changes in the environmental medium during formation in order to show friction- and wear-optimized behavior.The subsequently available processes for the functionalization of a-C:H tool coatings and homogenization of the aluminum passive layer will allow a selective optimization of the adhesion mechanisms of aluminum during forming operations. After completion of the project, a combination of both processes will enable the dry forming of aluminum alloys.
DFG Programme
Priority Programmes
