Structure and property optimization of Ni-containing AlCrSiN coatings by nano-multilayer construction

Abstract

AlCrSiN coatings with exceptional oxidation resistance are promising protective layers for cutting tools. Due to the inferior tribological properties at elevated temperatures, recently, tailoring of AlCrSiN by alloying has attracted widespread attention. The addition of Ni is a practical method to reduce friction and increase toughness. Whereas, the lower hardness of Ni-containing AlCrSiN coatings leads to poor wear resistance. Here, to optimize the phase structure of monolithic AlCrSiN–Ni for synergistic improvement of mechanical and tribological properties, the AlCrSiN–Ni/AlCrN multilayer was deposited by cathodic arc evaporation and investigated by combing X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, and ball-on-disc tribometer. Without the formation of wurtzite AlN, epitaxially grown AlCrSiN–Ni/AlCrN coatings obtain coherent interlayer interfaces and dual-phase cubic structure involving nitride and metallic Ni. Correspondingly, the hardness increases from 21.6 ± 0.8 GPa of AlCrSiN–Ni to 31.1 ± 0.7 GPa of AlCrSiN–Ni/AlCrN. Also, significant enhancement of scratch toughness was achieved by the multilayer. For wear tests at 600 °C, the multilayer exhibits an average friction coefficient of ∼0.81, which is between ∼0.95 of AlCrSiN and ∼0.61 of AlCrSiN–Ni. Furthermore, the superior mechanical properties upgrade the wear resistance of the coating. The wear rate at 600 °C for the multilayer is 3.9 × 10−6 mm3/N·m, while other monolithic coatings have a wear rate higher than 2.0 × 10−5 mm3/N·m.