Effect of bilayer period on properties of Cr/CrN multilayer coatings produced by laser ablation

Multilayers of alternate Cr/CrN coatings deposited on AISI 301 steel by a pulsed Nd:YAG laser have been tested by microindentation to measure both hardness and Young's modulus. Critical load L_C has been determined by scratch test. The total thickness of multilayers was 1 µm, and the bilayer period Λ varied from between 60 nm and 1000 nm. TEM and EDS techniques were used for investigating and analyzing the microstructure of the multilayers. The results of these measurements show that the mechanical properties of Cr/CrN multilayers depend on the bilayer period. The maximum improvement in performance over a single layer of CrN has been found to be Λ at 250 nm, particularly in terms of critical load and Young's modulus.