Understanding the structural, surface electronic bonding, optical, and mechanical features of sputtering deposited CrNiN coatings with Si and Al additives

Abstract Herein, the closed field unbalanced magnetron sputtered CrNiN, CrNiSiN, and CrNiAlN coatings are studied to gain insights into their structural, morphological, optical, and mechanical properties. Detailed characterizations of the thin films have been carried out through X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible–near infrared (UV–Vis) spectroscopy, nanoindentation, finite element modeling (FEM), and water contact angle measurements. XRD confirmed the hexagonal close-packed hcp-Cr2N (211) phase and face-centered cubic fcc-CrN (200) phase. The SEM images confirmed the compact, dense, and uniform distribution of gains in the coating structures. The average crystallite size of CrNiNcoatings was 515 nm. The addition of substituents (Si and Al) to the CrNiN coatings resulted in increasing the crystallite sizes to 605 nm (for CrNiSiN) and 811 nm (for CrNiAlN) as well as grain size from 1.32-2.335 μm. XPS analysis was conducted to estimate the atomic constituents and measure the high-resolution XPS spectra of Ni2p photoelectron lines. The average crystallite size was 515 nm for CrNiN, while the addition of substituents (Si and Al) to the CrNiN matrix resulted in increased crystallite sizes to 605 nm (CrNiSiN), and 811 nm (CrNiAlN) with grain sizes ranging from 1.32-2.33 μm. The elastic modulus and hardness of the coatings are between 361– 459 GPa, and 23.1–26.8 GPa, respectively. The Si, and Al additions enhanced both Young's modulus and the hardness of the coatings. Results of FEM modeling demonstrated the stress distribution within the coatings on steel and silicon substrates at different film thicknesses. The maximum stress level was increased by 30% at the coatings' upper portion, while that of the interface was reduced by 60%. The water contact angle values lay within the range of 102.4°–112.4°.