Structure, chemistry, and mechanical properties of non-reactively sputtered Ti-Al-N

Abstract

This study presents the influence of substrate temperature, sputtering conditions (DC and pulsed DC), and Al content on chemical composition, structure, growth morphology, mechanical properties and thermal stability of non-reactively sputtered Ti-Al-N coatings. The substrate temperature and the pulse frequency have a minor impact on the coating properties, which are more strongly influenced by the chemical composition of the target (Ti_0.5Al_0.5N, Ti_0.33Al_0.67N, or Ti_0.2Al_0.8N) and the duty cycle during pulsed DC sputtering. The highest deposition rate of 109 ± 2 nm/min was obtained from a single-phase cubic rock-salt-structured coating and the highest hardness of 38.2 ± 2.5 GPa from a two-phase-structure coating (cubic rock salt and minor hexagonal wurtzite structure), both prepared from the Ti_0.5Al_0.5N target. The maximum Al content (Ti_1-xAl_xN) for single-phase cubic rock-salt-structured coatings is x  = 0.64, and the minimum Al content for single-phase hexagonal wurtzite-structured coatings is x  = 0.81. The findings demonstrate that non-reactive sputtering is a viable method for preparing Ti-Al-N coatings. Furthermore, even without additional substrate heating, this approach achieves a high hardness of 33.6 ± 1.5 GPa and an impressive deposition rate of 102 ± 1 nm/min, offering a pathway to further enhance the sustainable production of these hard protective coatings.