Structure–property–wear relationships and failure mechanisms in TiAlN, AlCrN and AlTiCrN hard coatings for cutting tool applications: A review

Abstract

Hard nitride coatings are widely applied to cutting tools to improve wear resistance, thermal stability, and machining performance under severe thermo-mechanical conditions. This review critically examines TiAlN, AlCrN, and AlTiCrN coatings within a structure–property–wear–machining performance framework. The literature is analysed with emphasis on deposition techniques, microstructural evolution, mechanical and tribological behaviour, oxidation resistance, wear mechanisms, and cutting performance under dry and high-speed machining conditions. The review shows that ternary and multicomponent nitride systems provide additional composition and architecture dependent routes for improving high-temperature performance compared with earlier binary TiN-based coatings. TiAlN coatings benefit from spinodal decomposition-induced hardening and protective Al₂O₃ formation; however, their hardness and structural stability may deteriorate at approximately 800–900 °C because of the transformation of cubic AlN-rich domains into hexagonal AlN and oxidation-driven degradation. AlCrN coatings provide improved oxidation resistance and thermal stability through enhanced cubic phase stability and the formation of protective Al₂O₃/Cr₂O₃ scales. Selected AlTiCrN coatings may combine solid-solution strengthening, grain refinement, delayed phase transformation, and oxide-containing tribofilm formation, although the resulting performance depends strongly on composition, architecture, and deposition conditions. Wear of these coatings is governed by combined abrasive, adhesive, oxidation, diffusion, and delamination mechanisms, with oxidation and diffusion becoming increasingly dominant at high cutting temperatures. The review highlights that coating performance depends not only on composition but also on deposition-controlled defect density, adhesion, residual stress, and microstructural stability. Overall, TiAlN-, AlCrN-, and AlTiCrN-based coatings each offer useful performance within specific compositional and operating windows, while advanced ionized PVD techniques and high-entropy nitride systems provide promising directions for dry and high-speed machining applications.