TiSiN coatings are of high interest for the cutting industry, since they not only offer excellent mechanical properties, but also exhibit exceptional oxidation resistance. Although up to date several studies have been conducted on evaluating the oxidation resistance of nanocomposite TiSiN coatings, the influence of the shielding effect of the amorphous SiNx phase on the nanocrystalline TiN phase during oxidation has not yet been illuminated in detail. Therefore, the aim of this work is to provide insight into this shielding effect by using a threelayer SiNx/TiN/SiNx model system. Three different SiNx layer thicknesses of 150, 300 and 800 nm were investigated, while the TiN layer thickness was with 900 nm identical for all coatings. The results revealed that the amorphous SiNx efficiently shields TiN against oxidation up to temperatures exceeding 800 ◦C, whereby the exact oxidation onset temperature increased with increasing SiNx layer thickness. After reaching a critical temperature, both the TiN and amorphous SiNx phase were found to exhibit a porous structure, leading to oxidation of the TiN layer and growth of coarsened TiO2 grains, which eventually break the SiNx top layer. Furthermore, amorphous SiNx was shown to be significantly more resistant to oxidation compared to crystalline TiN, being still mainly non-oxidized after oxidation at 1200 ◦C for 30 min. The present study allows to gain insight into the underlying mechanisms of the shielding effect of amorphous SiNx on TiN using a model coating system, thus providing a
deeper understanding of the oxidation behavior of TiSiN nanocomposite coatings.