TiSiN/AlCrN multilayer coatings with gradient modulation period deposited by HiPIMS: Mechanical and tribological properties

Abstract

Hard nitride coatings with multilayer or gradient structures have been widely used in the field of machining, and their modulation period (Λ) plays a crucial role in it. In this study, high energy impulse magnetron sputtering (HiPIMS) was used to prepare four kinds of TiSiN/AlCrN multilayer coatings with different modulation periods and gradient variations in thickness (3.6–12.3 nm). The influence of Λ variation on the microstructure, mechanical properties, and wear resistance of coatings was studied. The coatings were mainly composed of fcc nanocrystals and a small amount of amorphous SiN_x. The smaller Λ and gradient design result in unclear interlayer interfaces and mutual diffusion, displaying a coherent interface at Λ = 4.6 nm. The gradient variation of modulation period significantly improves the mechanical properties of the coating. The coating with an increasing and then decreasing modulation period (G3 gradient structure) exhibits the best mechanical properties, with the highest hardness (38.4 GPa), bonding strength (68.2 N), H/E∗ (0.084), and H³/E∗² (0.380 GPa). Due to its high hardness and the presence of lubricating phases, G3 has the lowest wear rate (5 × 10⁻¹⁵ m³N⁻¹m⁻¹) and a lower friction coefficient (0.34).