Effect of the modulation geometry on mechanical and tribological properties of TiSiN/TiAlN nano-multilayer coatings

Abstract

Nano-multilayer architecture based on physical vapor deposition is a promising way to tailor the structural and mechanical properties of nitride hard coatings for cutting tool applications. In this work, the mechanical and tribological properties of TiSiN/TiAlN coatings with different modulation geometry, namely modulation period, Λ, and modulation ratio, λ, were elaborated. The TiSiN/TiAlN nano-multilayer with reduced Λ of 8.5 nm and λ of 1:2.3 (thickness ratio of TiAlN to TiSiN sublayer) shows a noticeable increase in hardness to 36.8 GPa. The modulation geometry impacts the wear behavior of TiSiN/TiAlN nano-multilayers through two aspects. Firstly, the mechanical enhancement effectively promotes the wear resistance of coatings at room temperature. Secondly, the chemical variation changes the wear mechanism at high temperatures. For the situation at 600 °C, the combined action of adhesive, abrasive, and oxidative wear gives rise to dispersive and small oxide patches, adhered to sliding surfaces for TiSiN/TiAlN coatings with higher λ of, for instance, 2.3:1. This tribolayer contributes to the lower wear volume loss than the case at room temperature for the TiSiN/TiAlN with a Λ of 29 nm and a λ of 2.3:1. In contrast, the TiSiN/TiAlN coating with a lower λ of 1:2.3 exhibits mild abrasive and oxidative wear at 600 °C.