SiNx-Submikrometerschichten – Parameteroptimierung –

SiN_x-submicrometer coatings – Optimization of the film properties – The influence of the deposition conditions on the properties of SiN_x-coatings was investigated. The characterized SiN_x-coatings were deposited by the help of reactive magnetron sputtering. Gas pressure and film thickness were varied. Scanning electron microscopic views of the cross sections show a columnar structure varying with the deposition parameters. The different structures are comparable to the known structure zone models. There is a transition from dense structures to open columnar structures with increasing gas pressure. The Microstructure of coatings also changes with increasing film thickness. Especially deposition conditions promoting shadowing effects lead to a large growth of the column diameter with increasing thickness. The intrinsic stresses and the ultramicrohardness of the coatings change with changing gas pressure, too. Dense structures have high intrinsic stresses and a high hardness while coarse columnar structures have low intrinsic stresses and a low hardness. The influence of the deposition parameters on wear behaviour and adhesion of the SiN_x-coatings was investigated by cavitation tests. Dense coatings with high intrinsic stresses show adhesion failures, and coatings with lower stresses and coarse columnar structures fail because of their lower intrinsic stability. Thus, there is an optimum gas pressure, at which the best properties are reached. It can be shown that with decreasing film thickness adhesion increases.     

Umformtechnologie: Prozesse – Werkstoff‐ charakterisierung – Simulation – Verifikation

Sheet forming technology – processes, materials, simulation and verification Hydroforming and Deep Drawing represent leading technologies for forming sheet metal components. The Materials Branch of the University of Duisburg‐Essen works since more than 10 years in the field of Hydroforming and showed that Hydroforming increases the strength and that the weldings of hydroformed tubes normally exhibit a same (fatigue) strength as the base material. For an improvement of the economics of hydroforming spliced tubes were considered and standard hollow nodes for tubes nodes structures were developed and a proposal was made to produce these tubes in variable tools with segments or lamellas. A significant increase in economics of Hydroforming and of Deep Drawing of components is achieved by an introduction of the principles of an integral (cooperative) development of products. At the University of Duisburg‐Essen the following stages are run through: CAD (the Material Branch uses PRO/ENGINEER®), forming simulation – for that PAM‐STAMP® (ESI) and PATRAN MARC MENTAT® (MSC) are used – FEM strength calculation and EVICD for a consideration of variable service loading. Forming simulation needs as basic material data the yield curve, the parameters of anisotropy and the Forming Limit Curve (FLC). For a determination of the FLC in Deep Drawing Tests suitable Nakazima specimens were developed by applying the principles of cooperative product development. The specimens could then successfully be validated in Deep Drawing Tests, which were instrumented by the advanced 3D‐forming‐analysis‐system AUTOGRID inProcess (VIALUX). Various other forming simulations were also performed and some general rules for the performance of forming simulations were formulated. Finally, reverse engineering is briefly discussed.