Abstract
Abstract Ternary hard coatings like TiAlN and CrAlN are used to improve the tool lifetime during cutting. The addition of silicon leads to a nanocomposite coating architecture with advantageous properties, like a higher oxidation stability and higher indentation hardness. The coating system TiAlCrSiON is a combination of TiAlN and CrAlN with added oxygen: This coating is not sufficiently studied yet. However, it has a great potential to improve the cutting performance and tool lifetime. In the current study, three different TiAlCrSiON nanolayer coatings were deposited by direct current magnetron sputtering/high power pulsed magnetron sputtering hybrid processes on an industrial coating unit using three different gas flow ratios of oxygen to nitrogen. Bases on these coatings the influence of the incorporation of oxygen into the TiAlCrSiON coatings on the coating process and properties as well as on the thermal and oxidation stability is studied. The morphology of the coatings was investigated by scanning electron microscopy and transmission electron microscopy. It becomes increasingly columnar, when oxygen is incorporated into the coating. The phase composition was examined by X-ray diffraction. The results indicate an incorporation of oxygen into the cubic crystal lattice. The coatings show a nanocomposite and a nanolayer coating architecture. The oxygen is distributed inhomogeneously over the coating thickness and homogeneously within the nanolayers. Moreover, the coatings were investigated by nanoindentation. When the oxygen content increases, the indentation hardness decreases from HIT = (34 ± 2) GPa for the nitride Ti21Al17Cr5Si3N54 coating to HIT = (26 ± 2) GPa for the oxynitride Ti23Al13Cr5Si3O21N35 coating with a high oxygen content. The coatings show a high phase stability even at T = 1200 °C. The oxidation stability of the oxynitride coating with a high oxygen content is decreased T = 900 °C compared to the nitride coating.
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