Deformation and Cracking Mechanism in CrN/TiN Multilayer Coatings

Ahmad Azizpour,Rainer Hahn,Fedor F Klimashin,Esmaeil Poursaeidi,Paul Heinz Mayrhofer,Tomasz Wojcik

doi:10.3390/coatings9060363

Abstract

In this study, the effects of the microstructural properties on the deformation and damage mechanism of CrN/TiN multilayer coatings deposited on Custom 450 steel using the unbalanced reactive magnetron sputtering PVD process were studied. All coatings were fabricated with an overall thickness of 1.5 µm, but different bilayer periods (Λ). Structural and mechanical properties of coatings were investigated by XRD analysis and nanoindentation experiment, respectively. Indentation tests at three loads of 100, 300, and 450 mN were performed on the coatings’ surface and then, cross-sections of fractured imprints were analyzed with SEM and TEM. Measuring the length of the cracks induced by indentation loads and analyzing the load-displacement curves, apparent fracture energy values of multilayer coatings were calculated. We observed that multilayer systems with bilayer periods of 4.5–15 nm possess superlattice structure, which also results in higher values for Young’s modulus and hardness as well as higher fracture energy. Comparison of cross-sectional SEM and TEM observations showed that coatings with smaller bilayer periods tend to deform by shear sliding mechanism due to the existence of the long-grown columns, while short dispersed grains—growing in the coatings with a larger bilayer period—led to deformation via local grain boundary sliding and grain rotation.

Highlights

Gas turbine compressors are prone to performance losses because of erosion of the compressor blades when being operated in regions with a dusty and sandy atmosphere and when sand, fly ash, salt, and ice crystals or volcanic ashes are ingested
The CrN/TiN multilayer coatings were deposited on Custom 450 steel, which is a tempered martensitic stainless steel frequently used in, e.g., axial compressor blades
The cracking and deformation mechanisms of the CrN/TiN multilayer coatings deposited on the GTD450 steel by reactive magnetron sputtering PVD method were investigated

Summary

Introduction

Gas turbine compressors are prone to performance losses because of erosion of the compressor blades when being operated in regions with a dusty and sandy atmosphere and when sand, fly ash, salt, and ice crystals or volcanic ashes are ingested. A wide variety of multilayer coatings comprising transition metal nitride layers such as TiN, CrN, TaN, MoN, and VN have been extensively studied due to their promising properties as high hardness, high melting temperatures, and good chemical and physical stability [1,2,3,4,5,6,7,8]. Amongst different transition metal layer combinations, CrN/TiN multilayer coatings have attracted great attention on the interrelation among their microstructure, morphology, and resulting mechanical properties [4,9,10,11,12,13,14,15,16,17].

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Results

Conclusion