Mechanical and Structural Properties of Nanocomposite CrAlSiN–AlSiN Coating with Periodically Modulated Composition

Lilyana Kolaklieva,Christo Bahchedjiev,Genoveva Atanasova,Plamen Stefanov,Tetyana Cholakova,Roumen Kakanakov,Stoyan Russev,Vasiliy Chitanov,Daniela Kovacheva

doi:10.3390/coatings10010041

Lilyana Kolaklieva, Christo Bahchedjiev + Show 7 more

Open Access

https://doi.org/10.3390/coatings10010041

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Abstract

A nanocomposite CrAlSiN–AlSiN coating with periodically modulated composition was developed and investigated regarding the effect of the composition and structure on the mechanical properties. The modulation was performed by variation of the pressure, cathode current and bias voltage during deposition. The structure and composition of the coating were investigated by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses. The coating had a nanocomposite structure consisting of (CrAl)N and (AlSi)N nanograins embedded in a Si3N4 matrix. The EDS analysis of the cross-section revealed that the period composition had changed from Cr051Al0.41Si0.08N to Al0.82Cr0.04Si0.14N. It was shown that the elastic modulus could be adjusted by composition modulation. The coating hardness of 54 GPa was obtained by nanoindentation. The modulated CrAlSiN–AlSiN coating exhibited improved elastic strain to failure (H/E* = 0.11, H—nanohardness, E*—the effective elastic modulus), excellent resistance to plastic deformation (H3/E*2 = 0.72), and elastic recovery of 70%, which suggested improved toughness.

Highlights

Various types of coatings, such as multicomponent, gradient, multilayer, and nanocomposite, have been used for many years for improving surface properties of industrial tools [1,2,3,4]
The CrAlSiN–AlSiN coating reported in this study has a nanocomposite structure consisting of an amorphous Si3 N4 matrix, in which nanocrystallites with sizes of 9 nm and 7 nm are incorporated
The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that nanocrystallites are composed of (CrAl)N and (AlSi)N

Summary

Introduction

Various types of coatings, such as multicomponent, gradient, multilayer, and nanocomposite, have been used for many years for improving surface properties of industrial tools [1,2,3,4]. Coatings combining enhanced mechanical properties (high hardness), improved tribological parameters (high wear resistance, a low friction coefficient), high temperature stability, better wear, and oxidation resistance have been subjected to intensive research. A wide range of applications require coatings with high hardness (>40 GPa) and toughness [5,6,7,8,9,10]. Superhard coatings exhibit lower plasticity, which results in lower toughness [11,12]. Matthews proposed the concept of nanocomposite coatings with high hardness and low elastic modulus, which can exhibit improved toughness and better wear resistance [13]. H/E (elastic strain to failure, E—elastic modulus) and H3 /E2 (resistance to plastic deformation), have been used as ranking parameters correlating to the wear resistance of the coatings [13,14].

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