High temperature investigation of the tribo mechanical behavior of TiAlSiN and CrAlSiN nanocomposite coatings

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PVD-coatings are an already established concept for the functionalization of surfaces of cheap substrate materials in order to improve the performance and service life of components without using solid components made of expensive special materials. Until now, tools coated by means of thin-film technology are frequently used in the cutting and cold forming industry, even though these coating systems do not offer sufficient wear resistance and mechanical properties at higher operating temperatures.By using nanocomposite layers, which are developed in the context of the proposed research project, the temperature limitations are expanded by alloying silicon in ternary coating systems (CrAlN and TiAlN) to obtain a thermal and oxidation resistant PVD-coating. Therefore, the influence of different process parameters and PVD technologies on TiAlSiN and CrAlSiN coatings is investigated to determine the correlations between the parameters and the resulting properties of the coating. Especially the influence of different substrate treatment methods, the silicon content, the target power, and the bias voltage on the morphological, mechanical and tribological properties at different temperature levels (20, 250 and 500°C) are closely investigated and evaluated. The investigations are completed by tests carried out in Taiwan, concerning the fatigue behavior at elevated temperatures. The deposition of the PVD coatings at the Institute of Materials Engineering are produced by using the magnetron sputtering process. At the same time, identical coating systems are deposited at a Taiwanese cooperating partner institute by means of an arc-evaporation process. This approach offers the opportunity to compare the different nanocomposite layers regarding their properties and to identify process specific characteristics. Finally, the layers (CrAlSiN and TiAlSiN) with the best properties of both different deposition processes are applied on forming tools and their performance is tested and evaluated in a real forming process with increased operating temperatures.