Wear behavior of nanometric CrN/Cr multilayers

Multilayered structures have attracted much attention as a way of improving the mechanical and tribological properties of hard protective coatings. We have previously reported results on nanometric chromium nitride (CrN)/Cr multilayers deposited by r.f. magnetron sputtering. It was observed that these multilayered structures improve the hardness of the CrN single layer coatings. Therefore, the next step has been the evaluation of the tribological behavior of these CrN/Cr multilayers, which is reported in this paper. The multilayers have been evaluated in their adhesion to the substrate, abrasive wear resistance and sliding wear behavior against alumina balls. The influence of different substrates on the tribological behavior of the coatings has also been investigated. It has been observed that the abrasive and sliding wear resistance of the multilayers greatly improves when decreasing the bilayer period thickness for a fixed overall coating thickness. The determining parameter on the sliding wear resistance has resulted to be the hardness, which is also known to be the main parameter on the abrasive wear behavior. The sliding wear mechanisms have been identified as abrasion, tribochemical wear and, in some cases, coating delamination. In the case of coatings deposited onto steel, it is also important the plastic deformation of the substrate during the test and the possible adhesion failure of the coatings.