Amplificação da dureza de estruturas de multicamadas de filmes finos CrN/Si3N4

Abstract

Surface engineering has been searching to attend the industrial demand for tools, parts and other components with larger lifecycles and higher wear resistance, by means of protective coatings whose mechanical, physical-chemical and tribological properties, such as hardness, friction, wear and corrosion and oxidation resistance can be optimized. One of the conditions that can influence directly these properties is the type of structure of the coating, as well as the temperature of the substrate during film deposition. In the present work were studied coatings composed by CrN/Si3N4 multilayers depositated on silicon substrate (001) at a temperature of 300°C, with varying bilayer periods between 2 and 10 nm. Several physicalchemical characterization techniques were used. Mechanical properties were assessed by nanoindentation tests. Films produced with single layers presented Cr/N ratio of 1.02 ± 0.05 and Si/N ratio of 0.74 ± 0.03, thus being considered stoichiometric and free from contaminants. CrN films attained 12 GPa hardness and Si3N4 films attained 26 GPa. Deposition parameters in which the single layers attained hardness values near to the maximum also contributed to the hardness increase, aim of this work. Amongst the multilayer periods evaluated, maximum hardness (H = 34.6 ± 1.27 GPa) was attained for a period of 4 nm, representing an increase of 40% in relation to Si3N4. Physical-chemical characterization techniques evinced the effective formation of a multilayer structure and enabled the determination of nanometric scale thicknesses, the distribution of elements as a function of depth, the chemical bonds present in the sample, as well as the steep interfacial characteristic. Furthermore, due to CrN crystalline structure and Si3N4 which is essentially amorphous, a condition predicted in the literature was satisfied, that is, the increase in hardness by the blocking of dislocation motion mechanism in crystalline-amorphous interfaces.