(AlCrNbSiTi)N/TiN multilayer films designed by a hybrid coating system combining high-power impulse magnetron sputtering and cathode arc deposition

Abstract

We designed a hybrid physical vapor deposition coating system equipped with high-power impulse magnetron sputtering (HiPIMS) and cathode arc deposition (CAD) systems. With this technique, we fabricated (AlCrNbSiTi)N/TiN multilayer films consisting of alternating layers of (AlCrNbSiTi)N, a high-entropy alloy nitride (HEAN) with enhanced thermal stability, and TiN, a material known for its high hardness. For this hybrid coating system, a new nucleation and growth model was proposed to explain the thin film deposition phenomenon. Film growth occurred through a self-induced repeated nucleation mechanism. The effects of the modulation period on the microstructural, mechanical, and oxidation resistance properties of the coatings were investigated using scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, and nanoindentation. All coatings exhibited a B1-NaCl-type face-centered cubic crystal structure. High-resolution TEM imaging revealed misfit dislocations between the HEAN and TiN layers and low-angle boundary dislocations between the subgrains. The 64-layer coating displayed outstanding mechanical, oxidation resistance, and tribological properties compared with those of previously reported multilayer coatings. The plastic deformation index, H3/E2, of the mono- and multilayer coatings increased from 0.17 to 0.37 GPa. After oxidation at 800 °C for 2 h in an ambient atmosphere, the thickness of the oxidation layer decreased from 1228 to 85 nm. Furthermore, the maximum flank wear of a coated tool after the milling test was less than that of the uncoated tool (201 vs. 528 μm), suggesting a large improvement in lifetime.