Dry milling of graphite in a ball mill represents a versatile one-step mechanochemical process for fabricating mechanochemically functionalized multilayer graphene (MG) bearing different functional groups. The variation of the milling parameters enables to control particle size, shape, functionality, specific surface area and dispersability of the MG functional fillers. In this study, MG was used as functional nanofiller for the production of SiC/MG nanocomposites. The nanocomposites exhibit significantly improved tribological behavior. The results of rotating pin on disc sliding tests show that with SiC/MG a noticeable improvement of friction and wear behavior under water-lubricated conditions like in slide bearings and face seals can be achieved. Sliding friction systems with the variant SiC+2% MG-CO 2 -120h appear to have the most promising tribological properties, due to the reduced size of the homogeneously distributed graphite particles, which promote the formation of advantageous surface states.

Thermoplastics combine high freedom of design with economical mass production. Metallic coatings on thermoplastics enable power and signal transmission, shield sensitive parts inside of housings and can reduce the temperature in critical areas by functioning as a heat sink. The most used technical thermoplastics are polyamides (PA), while the described use cases are often realized using Cu. Consequently, several studies tried to apply copper coatings on PA substrates via thermal spraying; so far, this combination is only feasible using an interlayer. In this study, a new approach to metallize thermoplastics via thermal spraying based on validated state-of-the-art predictions of the thermoplastics’ material response at relevant temperatures and strain rates is presented. Using these predictions, high velocity wire-arc spraying was selected as coating process. Furthermore, the process parameters were adapted to realize a continuous coating while also roughening the substrate during coating deposition. The resulting Cu coating on PA6 had a sufficiently high coating adhesion for post-treatment by grinding. The adhesion is achieved by in situ roughening during the coating application. The results indicate that different process parameters for initial layer deposition and further coating buildup are required due to the low thermal stability of PA6.

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The level of residual stresses is of great importance for many applications. In this work, the two established residual stress analysis methods x-ray stress analysis and incremental hole-drilling combined with electronic speckle pattern interferometry are compared. Each stress analysis method has its specific limitations. Furthermore, the residual stress state of a material is influenced by its processing history. To compare both methods, aluminum-based specimens (AlCu6Mn, AlZn5.5MgCu) with different processing histories were investigated. Measurements with both methods were conducted on the same specimens and on the same measurement spots. Highest stress levels were found in the mechanically machined specimen, while heat treatment via tempering or deposition welding shows reduced stress levels inside of the specimens. In case of cold spraying, the stresses in the feedstock material are considered negligible. In contrast, cold-spray coatings deposited on construction steel substrate exhibited tensile stresses, which relax over time at room temperature.

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