Experimental and predicted mechanical properties of Cr1−xAIxN thin films, at high temperatures, incorporating in situ synchrotron radiation X-ray diffraction and computational modelling

Cr1−xAlxN coatings, synthesised by an unbalanced magnetic sputtering system, showed improved microstructure and mechanical properties for ∼14–21% Al content. In situ SR-XRD analysis indicated various crystalline phases in the coatings that included: CrN, AlN, α-Cr with small amounts of AlO2 and Al2O3 over the 25–700 °C range. Al doping improves resistance to crystal growth, stress release and oxidation resistance of the coatings. Al doping also enhances the coating hardness (H) from 29 to 42 GPa, elastic modulus (E) from 378 to 438 GPa and increased the resistance to deformation. First-principles and quasi-harmonic approximation (QHA) studies on bulk CrN and AlN were incorporated to predict the thermo-elastic properties of Cr1−xAlxN thin film coatings in the temperature range of 0–1500 °C. The simulated results at T = 1500 °C give a predicted hardness of H = ∼41.5 GPa for a ∼21% Al doped Cr1−xAlxN coating.