EDS line scan profiles were performed across the coating–substrate interface to analyse the interface and subsurface
chemical characteristics. The results are shown in Fig. 11. As can be seen from the two line scan results, there is an approximately
1 lm region of interface that is rich in titanium, aluminium, iron, and some nitrogen for the TiAlN coated specimen
(Fig. 11a), while the interface region for the multilayer TiAlN/CrN coated specimen (Fig. 11b) is also approximately 1 lm and
is rich in titanium, aluminium, chromium, iron, and some nitrogen. Both results show the existence of a region with diffused
characteristics (near the subsurface), which can influence the stress gradients between the coating and its substrate, thus the
behaviour of fatigue cracks.