Relationship between nitrogen content and mechanical properties in Al1-xCrxNy thin films

To get further insight into Nitrogen stoichiometry influence which is of utmost importance since it influences the phase structure and consequently the mechanical properties of the AlCrN coatings, we carried out a systematically study of AlCrN coatings comprising coatings production, mechanical properties survey, and composition and phase structure characterizations. Al1-xCrxNy thin films have been synthesized by two physical vapour deposition - PVD systems: ion-beam (IBS) and magnetron sputtering (MS). Composition of the coatings was studied by both Energy Dispersive X- ray Spectrometer (EDXS) and Rutherford Backscattering Spectroscopy (RBS), the latter technique being very sensitive to light elements such as nitrogen. Most compositions are revealed to be sub- stoichiometric with Nitrogen (y < 1) which content decreases continuously as Chromium content (x) increases. This result has been analyzed thanks to TRIM's simulation and emphasizes the re- sputtering phenomena of nitrogen during the growth depending on the Al/ Cr ratio of the target. All the films are under compressive residual stresses with changes of the stress- free lattice parameter with the nitrogen content. Hardness of the films is in the range of 15 to 27 GPa while the tribological properties of Al1-xCrxNy films show a similar coefficients of friction (COF) evolution with average values observed between 0.4 - 0.8 depending on the nitrogen content.