Influence of Ag Target Power on Microstructure and Properties of TiN-Si3N4-Ag Composite Coatings

Abstract

TiN coatings are one of the most widely used nitride coatings. The introduction of the light metal element Si has led to the formation of TiN-Si₃N₄ coatings with a two-phase nanocomposite structure. However, the high friction coefficient of TiN-Si₃N₄ coatings at room temperature limits their application. In order to further improve its lubrication properties, we tried to incorporate the lubricating phase Ag. TiN-Si₃N₄-Ag composite coatings were prepared using a multi-target magnetron sputtering by fixing the Ti-Si target power and adjusting the Ag target power. Their microstructure, mechanical and tribological properties depending on the Ag target power were investigated. The results showed that the TiN-Si₃N₄-Ag composite coatings exhibited the crystalline TiN and Ag phase, and amorphous Si₃N₄ phase. The increasing Ag target power increased the coating surface roughness from 7 to 52 nm. The nano-hardness (H), elastic modulus (E), resistance against elastic strain to failure (H/E), and the resistance against plastic strain to failure (H³/E²) of the TiN-Si₃N₄-Ag composite coating first increased and then decreased with the increase of Ag target power. As the Ag target power was 10 W, the hardness (9.43 ± 0.45 GPa), elastic modulus (265.29 ± 13.3 GPa), H/E (0.036), and H³/E² (0.0119 GPa) of the TiN-Si₃N₄-Ag composite coating reached the maximum values, indicating this coating exhibiting the better mechanical properties. After adding Ag, the coating exhibited better lubricating effect, while the wear resistance of the coating increased.