Tribological Properties of CrN/AlN Films Produced by Reactive Magnetron Sputtering

Abstract

The microstructure of CrN/AlN films, prepared by reactive magnetron sputtering under various conditions, was analyzed and related to the wear behavior of the films. One set of films was prepared by conventional reactive magnetron sputtering, a second set adding an extra amount of reactive gas to the initial Ar + N 2 mixture and a third set adding an extra source of nitrogen near the substrate during sputtering. The samples were analyzed by scanning electron microscopy + energy dispersive microanalysis, high resolution scanning electron microscopy, atomic force microscopy, and x-ray diffraction. The results of the microstructural analysis revealed a clear difference in the morphology growth of the films when extra nitrogen was used compared to the conventionally prepared films. Formation of CrN was significantly faster than that of AlN. The most effective method to produce AlN was to introduce extra nitrogen. Pin-on-disk wear experiments were carried out in ambient air, to investigate the tribological behavior of the CrN/AlN system against a steel ball under dry conditions for various loads and a constant sliding speed. The results revealed that tribological properties of the layers improved unlike those of the untreated H13 steel. The friction behavior is closely related to the structure of the deposited films. The thicker CrN layer contributed to the higher load capacity of the coated steel when compared to the unmodified steel. However, wear life for the coating system was very short, denoted by the fairly poor adhesion of the film system to the steel substrate.

Oxidation behavior of AlN/CrN multilayered hard coatings

“…The latter is due to the formation of a dense chemically stable oxide scale, which retards further oxidation by suppressing the supply of oxide-forming metallic elements [ 2 , 5 ]. Coatings composed of alternating AlN/CrN layers show further enhancement of mechanical properties as compared to the CrAlN system [ 6 – 9 ]. Additionally, an improved oxidation resistance was observed in particular for AlN/CrN superlattice coatings with bilayer periods ≤4 nm [ 10 – 13 ].…”

New Plasma Surface Processing Technology and its Application

“…However, conventional DC magnetron sputtering produced low metal ionization rate and poor film quality, which can not meet the requirements of new parts or devices. Therefore, how to improve the quality of the film is very important, some studies found that a certain amount of heat and energy in the surface of the film growth could improve the quality of the film [3,4], such as the substrate heating, a negative bias [5] and increasing the degree of ionization [6] and so on.…”