Key Takeaways & Executive Findings
- •• VN/TiN−Ni nano-multilayered films with a deposition time ratio of 10:12 achieve a hardness of 25.9 GPa, elastic modulus of 317 GPa, and fracture toughness of 1.88 MPa·m1/2. • Fracture toughness is improved by approximately 50% compared to monolithic VN films, attributed to coherent interfaces and phase separation in the TiN−Ni layer. • The TiN−Ni layer grows epitaxially on the VN layer, forming a coherent interface that enhances mechanical properties. • Modulation layer thickness critically influences the microstructure and mechanical behavior of the nano-multilayered films.
Abstract
The dependence of interface structure and mechanical properties on the modulation layer thickness of VN/TiN−Ni nano-multilayered films deposited on Si substrates using a reactive magnetron sputtering technique was systematically investigated. The films were characterized using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and nanoindentation. The results show that the TiN−Ni layer grows epitaxially on the VN layer, forming a coherent interface between the two sublayers. When the deposition time ratio of the two sublayers (TTiN−Ni꞉TVN) is 10꞉12, the films exhibit remarkable mechanical properties, with hardness, elastic modulus, and fracture toughness values of 25.9 GPa, 317 GPa, and 1.88 MPa·m1/2, respectively. Meanwhile, fracture toughness is improved by approximately 50% compared to the VN monolithic film. This enhancement is attributed to the coherent interface between the sublayers and the phase separation in the TiN−Ni layer.
1. Introduction
Nanostructured nitride films, such as vanadium nitride (VN) and titanium nitride (TiN), are increasingly employed in the machining and forming tool industries because of their excellent hardness, thermal stability, and wear resistance [1−3]. However, since hardness and fracture toughness are typically inversely related, the low intrinsic fracture toughness of these films limits their practical applications [4,5]. As a result, considerable research has focused on overcoming this trade-off [6,7].
In nano-multilayered films, the thickness of individual layers plays a crucial role in determining the properties of each constituent layer. Consequently, the characteristics of each layer and the thickness of the bilayer unit are key factors in determining the overall properties of the final films [8,9]. Furthermore, the nano-multilayered structure can hinder columnar grain growth and combine the advantages of each sublayer. These films often exhibit significant improvements in mechanical properties compared to monolithic films, owing to the interface structures and the complex interactions between the layers [10–12]. For example, PAN et al [13] fabricated VN/TiB2 nano-multilayered films with different modulation ratios (tVN꞉tTiB2) using magnetron sputtering. When the ratio was 1꞉7, the films displayed remarkable hardness and elastic modulus of 41.8 GPa and 492.4 GPa, respectively. The molecular dynamics simulations were also conducted to study V/VN nano-multilayered films with varying modulation periods [14]. The results showed that films with larger modulation period (Λ) values exhibited higher elastic modulus, greater elastic limits, and improved lattice integrity. Notably, strain hardening was observed when Λ≥42.9 Å. In another study, WANG et al [15] deposited monolithic AlCrSiN, VN, and AlCrSiN/VN nano-multilayered films using arc ion plating and magnetron sputtering. The nano-multilayered films demonstrated the highest hardness of 30.7 GPa, attributed to the interfacial enhancement mechanism and higher compressive stress. The interfacial structure of these multilayers was influenced by the modulation period and crystal structure, leading to significant improvements in mechanical properties compared to monolithic films.
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Wen-jie CHENG, Ping LIU, Xin-fa ZHU, Yi MENG, Hong-mei LU, Peter K. LIAW, Wei LI (2025). Effects of modulation layer thickness on microstructures and mechanical behavior of VN/TiN−Ni nano-multilayered films. SinoTechIntel Verified Research. https://doi.org/10.1016/S1003-6326(25)66983-4
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Frequently Asked Questions
What are the optimal deposition time ratios for VN/TiN−Ni nano-multilayered films to achieve high mechanical properties?
The optimal deposition time ratio is TTiN−Ni:TVN = 10:12, which yields a hardness of 25.9 GPa, elastic modulus of 317 GPa, and fracture toughness of 1.88 MPa·m1/2.
How does the modulation layer thickness affect the microstructure of VN/TiN−Ni films?
The modulation layer thickness influences the epitaxial growth of TiN−Ni on VN, forming coherent interfaces. This structural feature enhances mechanical properties by promoting phase separation and hindering columnar grain growth.
What is the improvement in fracture toughness compared to monolithic VN films?
The fracture toughness of the VN/TiN−Ni nano-multilayered films is improved by approximately 50% compared to monolithic VN films.
What characterization techniques were used in this study?
The films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and nanoindentation.
What is the main mechanism behind the enhanced mechanical properties?
The enhancement is attributed to the coherent interface between the sublayers and the phase separation in the TiN−Ni layer, which together improve hardness and fracture toughness.
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