Project Details
Projekt
Functionalising of a-C:H tool coatings and homogenization of the aluminum passive layer for the dry forming of aluminum
Subject Area
Primary Shaping and Reshaping Technology, Additive Manufacturing
Term
from 2017 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 390892986
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
