Tuning the mechanical properties and toughness of TiAlN coatings deposited by low duty cycle pulsed magnetron sputtering from a rotating cylindrical target

Abstract

Despite the promising capabilities, rotating cylindrical magnetron sputtering (CMS) has been relatively rarely described in the literature, especially regarding hard protective coating applications. In this study, we investigate the use of CMS in the pulsed dc mode with very low duty cycle (<10 %) to prepare model TiAlN coatings at relatively high deposition rates (4 μm/h). We examine the impact of key parameters, specifically, substrate bias and substrate temperature on the coating microstructure and properties. Particularly, we focus on the residual stress in the coatings and their nanoindentation toughness, as these characteristics are crucial for the understanding of the film behavior and optimizing coating architectures. TiAlN coatings prepared with a substrate bias of about −100 V exhibit dense morphology, and high hardness (28–30 GPa), while the level of compressive stress in the coatings can be significantly reduced by increasing substrate temperature (from −5.6 GPa to −2.3 GPa at room temperature and 400 °C, respectively). Furthermore, we show a linear relationship between the residual stress in the TiAlN coatings and their nanoindentation toughness (1.1 MPa·m^1/2 to 5.1 MPa·m^1/2). Our findings demonstrate that both substrate bias and temperature can be effectively used to control the microstructure, mechanical properties, toughness and compressive stress level in the coatings, thereby opening a possibility to mitigate loading stress in various applications.