Mechanical and tribological properties of CrN/Ag and CrSiN/Ag nanoscale multilayers

This paper presents a concept of combining hard CrN (or CrSiN) and soft Ag lubricating materials in a nanoscale multilayer structure. The CrN/Ag and CrSiN/Ag multilayers are synthesized by reactive direct current (DC) magnetron sputtering techniques. The thickness of the Ag nanolayer in the multilayers is fixed to 4 nm while that of CrN and CrSiN nanolayers vary from 4 to 20 nm. The nitride layer effects on the mechanical and tribological properties of the multilayers have been investigated. Different mechanisms of the adhesion failure have been observed on the multilayer surfaces, depending on the nitride nanolayer types and their thicknesses. The CrSiN/Ag films exhibit poor adhesion whereas CrN/Ag multilayers demonstrate very good adhesion to AISI M2 steel substrates. The study of friction behaviors of the CrN/Ag multilayers against 100Cr6 steel balls reveals that the multilayers have low friction coefficients in comparison with that of a CrN single layer. The decrease of friction coefficients is related to the presence of the solid lubricant (Ag) nanolayer in the coatings.