Functionalising of a-C:H tool coatings and homogenization of the aluminum passive layer for the dry forming of aluminum

该项目旨在通过开发表面处理技术实现铝合金板材的干式成形，以优化工具和金属板材的边界表面。在成形过程中，某些磨损机制导致快速工具失效，并阻碍铝的干式成形的利用。这些机制可以通过碳基工具涂层的磨合行为来解释，并且与铝板的自然钝化有关。非晶碳氢化合物涂层（a-C：H）在与铝的干滑动接触中表现出非常好的摩擦学性能。然而，磨合行为的特征在于高粘附趋势和摩擦值。根据初步的测试，磨合行为是一个单一的和暂时的阶段。在磨合阶段期间，a-C：H涂层将被官能化，这导致降低的粘附趋势。作为该项目的一部分，将开发用于a-C：H涂层合成功能化的表面处理。因此，涂层的粗糙度将降低到几个纳米，a-C：H生长区将通过工具表面的等离子体抛光和a-C：H涂层的等离子体化学蚀刻来去除。之后，a-C：H界面将通过闪光灯退火热石墨化。这些过程具有高度的材料特异性。因此，它们将分别进行优化，随后结合到表面处理工艺中。自然生成的氢氧化铝钝化层显示出有利的摩擦学性能，并将通过对金属板表面上的自然钝化层进行定向均匀调整来合成。因此，现有的氧化物层将优选被γ-AlOOH代替，以利用γ-AlOOH在金属板表面内的减摩性能。合成的钝化层通过非常适合的金属板预处理来替代有利的水润滑。氧化层将在成形过程中通过环境介质的变化进行改性，以显示出摩擦和磨损优化的行为。随后可用的a-C：H工具涂层功能化和铝钝化层均匀化工艺将允许在成形操作期间选择性地优化铝的粘附机制。项目完成后，两种工艺的结合将使铝合金的干法成型成为可能。

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.