Gaseous ternary chromium-aluminium complexes as precursor for chemical vapour deposition.

Research on high-performance CVD coatings follows the target to increased hardness and oxidation resistance. Such coatings and coating systems are required for machining tools to optimize the manufacturing parameters for new materials and new processes. The use of chromium-containing coatings is requested because of its feature to increase the corrosion resistance. The production of various chromium-containing coatings is already shown by PVD, but for industrial scale CVD processes there are problems with the chromium precursors. Especially the chromium chlorides have a low vapour pressure and therefore high temperatures are needed for evaporation. To overcome the disadvantages of CrCl3 the relatively good evaporation of halide complexes was reported, showing potential for new CVD processes. Numerous metal compounds form gaseous complexes with Aluminium chloride but also Cr. Based on this characteristic the transport reaction of CrCl2/Al2Cl6 as chromium tetrachloraluminate is investigated. The focus of this work lies in the preparation of the chromium precursors as well as in the optimization of the transport reaction which required various changes in the conventional experimental CVD-setup. To measure the amount of transported chromium the gas phase was condensed and their Cr-content was analyzed. For the CVD deposition of Cr containing coatings, this precursor gas flow can be used directly. Further the interaction between aluminum chloride and the chromium precursor, different process parameters, as well as existing difficulties regarding the transport reaction are discussed. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]