Effects of Deposition Pressure on the Microstructure,Mechanical Behavior and High-Temperature Oxidation Resistance of AlCrTiSiN Coatings

Abstract

Deposition pressure is an important process parameter for coating preparation. To study its influence on the microstructure, mechanical properties and high-temperature oxidation resistance of AlCrTiSiN nanocomposite coatings, two types of AlCrTiSiN nanocomposite coatings were prepared using RF magnetron sputtering and pulse DC magnetron sputtering composite technologies at different deposition pressures(0.6, 0.8 Pa). Comparative analyses of the structure and properties of two types of coatings were performed using X-ray diffractometer(XRD), scanning electron microscope(SEM) equipped with an energy dispersive spectrometer(EDS) and nanoindenter. Results showed that the phase structure of the coatings prepared under two kinds of deposition pressures was fcc-(Al, Cr, Ti) N, which grew preferentially along the(111) crystal plane. However, the larger(111) texture coefficient of the coating prepared at 0.8 Pa indicated that the preferred orientation was more pronounced. Compared to the coating prepared at the deposition pressure of 0.8 Pa, the coating prepared at 0.6 Pa was characterized by finer surface particles, a denser coating and better mechanical properties, including better resistance to elastic and plastic deformation, as well as better adhesion between film and substrate. This was partly because the deposited particles reached the substrate with greater energy at the lower deposition pressure. On the other hand, a thicker and softer Si3N4 phase might have been present in the coating prepared at 0.8 Pa. After oxidation at 900 ℃ for 6 h, a continuous and dense Al2O3 mixed oxide film had formed on the surface of the coating, effectively preventing the diffusion of oxygen into the coating and protecting the coating under the oxide film. With the increase in deposition pressure from 0.6 to 0.8 Pa, the oxide particles increased, the thickness of the oxide film increased, and the high-temperature oxidation resistance decreased.

Keywords

• magnetron sputtering; deposition pressure; microstructure; mechanical property; high-temperature oxidation resistance