Chemical and mechanical stability of air annealed cathodic arc evaporated CrAlON coatings

Abstract

This study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-ON coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800ºC up to 1100 ºC have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+O3-. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 ºC the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings.

Quo Vadis: AlCr-Based Coatings in Industrial Applications

“…A cubic oxide structure (gamma or fcc) grows at a low Cr/(Cr + Al) content, whereas a hexagonal oxide structure (alpha) is predominant at a higher Cr/(Cr + Al) content. The formation of an oxide coating structure with a dominating fcc phase has also been reported a number of times [166,179,180]. The lowest reported value to obtain a pure corundum phase was Cr/(Cr + Al) = 0.3 [178].…”

Characterization of AlCrN and AlCrON Coatings Deposited on Plasma Nitrided AISI H13 Steels Using Ion-Source-Enhanced Arc Ion Plating

“…The addition of oxygen into the AlCrN coating considerably influences the hardness and elastic modulus of the coating. Due to the smaller ratio of anion vacancies or solid solution strengthing effect, the hadness would increase by doping a small amount of oxygen, while there is a progressive decrease of hardness with increasing oxygent content [35]. Actually, the compositions of the coatings have a significant influence on the hardness, including Cr and Al contents [14,28].…”