In the last 30 years, thin hard coatings were intensively investigated due to their high-performance characteristics:
high wear resistance, low friction coefficient and good thermal stability. Performances were
furthermore improved using multilayer configurations, although often limited by feasibility or cost considerations.
One of the main problems to overcome was the low corrosion protection that these coatings
assure to the tool steel substrates on which they are applied. To assure high performances and corrosion
protection it is possible to employ a completely new approach, suitable either as a pre-treatment of the
substrate or as top coating, by using materials of different nature in the form of nano-layers.
Monolayer and multilayer coatings obtained by PVD (Physical Vapor Deposition, using reactive arc
evaporation) and by PVD + ALD (Atomic Layer Deposition) were studied and compared. Both in-depth
composition and corrosion resistance properties were investigated using SEM–EDXS, GDOES (Glow Discharge
Optical Emission Spectrometry) and polarization curves in a 0.2 M NaCl solution. The coatings
studied were a TiAlN/TiN bi-layer and a TiCN monolayer obtained by PVD and an Al2O3 nano-layer
obtained by ALD.
