Crystallographic aspects related to advanced tribological multilayers of Cr/CrN and Ti/TiN types produced by pulsed laser deposition (PLD)

The microstructure of the Cr/CrN and Ti/TiN multilayers coatings deposited with the pulsed laser deposition (PLD) technique was studied using transmission electron microscope Philips CM20 TWIN (200 kV). It was found that the metallic buffer layers are characterized by the smallest columnar crystallite size and the highest defect density; this might rise their hardness but compromise the coating adhesion. The intermediate metallic layers showed a larger and less defected columnar structure as compared with the nitride layers, what should improve the coatings toughness. The scratch test performed with a Rockwell penetrator of 200 μm diameter loaded from 0.03 N up to 20 N indicated that the switching from a single layer to a multilayered metal/nitride coating of the same thickness improved the resistance to scratch test in case of Ti/TiN from 16.4 N for a TiN single layered to 22.9 N for a 32 layered coating and Cr/CrN from 4.4 N for a CrN single layered to 6.6 for a 32 layered ones.