Abstract
Multifunctional coatings, widely used in tribological applications, have their properties strongly influenced by the interaction of the system coating/substrate. The use of multilayered coatings has been pointed out as a solution for the problem of high internal stresses that can be generated in coated systems, in particular in the case of soft substrates. In multilayered coatings, a decrease in the stress gradient between substrate and coating improves adhesion. Moreover, the thickness of the coating has shown a strong influence on the tribological behaviour of the coated system. This paper, through widely used and efficient techniques, seeks to assess the influence of the thickness of different layers (DLC and CrN) on the response of a multifunctional coating. Si rich DLC and CrN coatings with different thicknesses were deposited on a steel substrate (AISI 1020) by Plasma Enhanced Magnetron Sputtering (PECVD). Scanning electron microscopy (SEM) and Raman spectroscopy (RS) were used in order to characterize the chemical composition and microstructure of the coatings. Instrumented indentation and scratch test techniques were used to measure hardness, elastic modulus, and adhesion of each layer. Critical loads were determined by visual analysis, using SEM in conjunction with the curves obtained in the scratch tests. The evaluation of the effect of the thicknesses of the layers allowed an optimised design of the multifunctional coated systems with improved durability.
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