Compressive deformation and failure of CrAlN/Si3N4 nanocomposite coatings

The deformation and failure mechanisms of CrAlN/Si3N4 coatings containing grains a few nanometres in size have been compared with those of conventional CrN-based coatings. It is shown that the addition of amorphous Si3N4 phase increased the yield stress and hardness of the coating material, but did not change their ratio. This is consistent with theoretical predictions using existing models. However, cracking in conventional CrN-based coatings was catastrophic, whereas that in the fine-grained CrAlN/Si3N4 structure was much more benign, suggesting that the improved performance of these materials is associated with their fracture behaviours.