Structure and thermal properties of TiAlN/CrN multilayered coatings with various modulation ratios

Multilayer architecture is an effective method to tailor the microstructure and properties of wear resistance coatings. Here, the CrN insertion layer is introduced into TiAlN coating to improve its mechanical and thermal properties by multilayer architecture. We deposited TiAlN/CrN_1 and _2 multilayered coatings with similar modulation period, where the TiAlN/CrN_1 coating exhibits a lower modulation ratio of CrN to TiAlN than TiAlN/CrN_2 coating. The epitaxial growth of TiAlN/CrN coating between TiAlN and CrN sublayers results in a single-phase cubic structure of our TiAlN/CrN multilayered coatings and causes an increased hardness to 31.7 ± 1.0 GPa for TiAlN/CrN_1. The CrN insertion layer has a beneficial effect on the thermal stability, which promotes the spinodal decomposition but retards the formation of stable phase wurtzite AlN during annealing. Additionally, the oxidation resistance of TiAlN coating is improved by the CrN insertion layer, whereas the TiAlN/CrN_2 coating exhibits better oxidation resistance than TiAlN/CrN_1 due to the thicker CrN sublayer.