Structure and mechanical properties of Ti-Al-Si-N protective coatings deposited from separated plasma of a vacuum arc

Protective coatings of the Ti-Al-Si-N system have been deposited from vacuum arc by sputtering a cathode of composition 78Ti-16Al-6Si in nitrogen. The coatings of the Ti-Al-Si-N system have been studied using X-ray diffraction analysis to examine phase compositions and substructure, atomic force microscopy to analyze the topography, X-ray fluorescence to define the chemical composition, and nanoindentation to measure hardness and elastic modulus. It has been found that as the nitrogen pressure in the deposition chamber increases, in the Ti-Al-Si-N system the transition from nanocrystalline (to 0.04 Pa) to nanocomposite (0.04-0.66 Pa) and X-ray amorphous (0.66-1.1 Pa) coatings takes place, and at a pressure of 2.7 Pa, the amount of the crystalline phase abruptly increases again. The highest mechanical characteristics and thermal stability have been shown by a coating having the nanocrystalline structure and nanocomposite coatings with a low content of amorphous phase, whose hardness attains 47 GPa.