High-entropy Alloy Nitride Research Articles

Corrigendum to “Effects of nitrogen content on microstructures and mechanical properties of (AlCrTiZrHf)N high-entropy alloy nitride films”

Corrigendum to “Effects of nitrogen content on microstructures and mechanical properties of (AlCrTiZrHf)N high-entropy alloy nitride films”

Effects of nitrogen content on microstructures and mechanical properties of (AlCrTiZrHf)N high-entropy alloy nitride films

The (AlCrTiZrHf)N high-entropy alloy nitride films were synthesized by reactive magnetron sputtering. The effects of different N2 flow rates on the microstructures and mechanical properties of (AlCrTiZrHf)N films were studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nanoindentation, coating friction and wear tester. The results show that the AlCrTiZrHf high-entropy alloy film presents an amorphous state. With the increase of the N2 flow rate, the (AlCrTiZrHf)N high-entropy alloy nitride films transform to a face-centered-cubic (FCC) structure. When the N2:Ar ratio is 5:4, the hardness and elastic modulus of the films reach 33.1 GPa and 347.3 GPa, respectively. The strengthening effect is mainly attributed to the formation of saturated metal-nitride phases and the solid-solution strengthening of various elements. Meanwhile, the (AlCrTiZrHf)N film exhibits the low friction coefficient and superior wear resistance. Based on the excellent properties of high-entropy alloy nitride films, the (AlCrTiZrHf)N film presents a potential application in protective coating.

Nanostructured and mechanical properties of high-entropy alloy nitride films prepared by magnetron sputtering at different substrate temperatures

ABSTRACT(AlCrNbSiTiV)N high-entropy alloy (HEA) nitride coatings have been grown on cermet tools inserts and glass substrates. Using reactive direct current magnetron sputtering with an equimolar AlCrNbSiTiV HEA target and Ar plasma and N2 reactive gases. In this study, the influence of (AlCrNbSiTiV)N coatings varied substrate temperature (room, 100, 200, 300, 400°C), on the structure, mechanical properties and cutting performance of the cermet cutting tools was investigated in dry machining of a SCM440 steel. The (AlCrNbSiTiV)N films coated was homogeneous, very compact and shows good adhesion strength (classified as HF1). The TEM image results indicate that the (AlCrNbSiTiV)N films are simple face-centre-cubic structures. As the substrate temperature increases, the films hardness increases, reaching the maximum value of 2493 HV at 100°C, and then decreases with further increase in the substrate temperature. The cutting performance improves when coated tools are used. The machined surface with the coated tool using a substrate temperature 100°C deposition parameters, show less surface defects and the tool flank wear is reduced.

Microstructural change and phase transformation in each individual layer of a nano-multilayered AlCrTiSiN high-entropy alloy nitride coating upon annealing

A high-performance AlCrTiSiN high-entropy alloy (HEA) nitride coating, consisting of a columnar CrN (BL-1), a nano-multilayered CrN/AlCrN (BL-2), a columnar AlCrN (TL) and a nano-multilayered AlCrTiSiN HEA nitride layer (HEA-NL) towards to surface, was isochronally annealed at 700 °C ∼ 900 °C. Microstructural change and phase transformation of each individual layer of the HEA nitride coating were studied, as well as microstructure-property relationship. Phase transformation sequence of CrN → Cr2N → Cr → σ-CrFe occurs in the BL-1 by nucleation and growth upon annealing, whereas the fcc-AlCrN solid solution of the BL-2 adopts a two-step phase transformation sequence: first to enriched-Al and enriched-Cr fcc-domains by interface-directed spinodal decomposition, and subsequently to hcp-AlN and σ-CrFe by recrystallization, accompanied by the dissolution of layered structure and the diffusion of Fe deriving from steel substrate. The TL shows two different features from that of the BL-2: (i) there is a precipitation process of hcp-AlN from the fcc-AlCrN; (ii) the spinodal decomposition is isotropic spinodal decomposition. The HEA-NL shows drastic differences in spinodal decomposition behavior and microstructure compared to the TL, in which interface-directed spinodal decomposition produces a triple-layer consisting of a rich-Cr/Ti layer fcc-domains confined by two enriched-AlN ones, simultaneously resulting in a notable self-hardening. Subsequently recrystallization results in a aging softening at 900 °C due to the dissolution of nano-multilayered structure, the phase transformation of enriched-Al fcc-domain to hcp-AlN and the formation of soft Cr. Moreover, both Cr2N and σ-phase layers deteriorate the adhesion strength.

Effects of deposition parameters on the structure and mechanical properties of high-entropy alloy nitride films

High-entropy alloy (AlCrNbSiTiV)N nitride films are prepared using direct current (dc) reactive magnetron sputtering, with an equiatomic AlCrNbSiTiV alloy target. Experiments using the grey-Taguchi method are conducted to determine the effect of deposition parameters (dc power, substrate temperature, N2/(N2+Ar) flow rate and substrate bias) on the microstructure, mechanical and tribological properties. Orthogonal array (L9 34), signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. The coated films are examined using scanning electron microscopy, an atomic force microscope, transmission electron microscopy (TEM), a tribometer and a nanoindenter. The TEM patterns confirm that the (AlCrNbSiTiV)N nitride films have a simple face-center-cubic structure. The experimental results show that a (AlCrNbSiTiV)N film coating significantly improves the mechanical properties. In the confirmation runs, using grey relational analysis, the improvement in friction coefficient is 32.5%, in corrosion current is 28.6%, in hardness H is 29.4%, in elastic modulus E is −18.3%, in H/E is 57.1 and in H3/E2 is 225.0%. The samples with (AlCrNbSiTiV)N film coating are classified as HF1 and exhibit good adhesive strength.

Growth (AlCrNbSiTiV)N thin films on the interrupted turning and properties using DCMS and HIPIMS system

This paper determines the optimal settings in the deposition parameters for (AlCrNbSiTiV)N high-entropy alloy (HEAs) nitride films that are deposited on CBN cutting tools and glass substrates. We use direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HIPIMS), with Ar plasma and N2 reactive gases. Experiments with the grey-Taguchi method are conducted to determine the effect of deposition parameters (deposition time, substrate DC bias, DC power and substratetemperature) on interrupted turning 50CrMo4 steel machining and the films’ structural properties. Experimental result shows that the multiple performance characteristics for these (AlCrNbSiTiV)N HEAs film coatings can be improved using the grey-Taguchi method. As can be seen, the coated film is homogeneous, very compact and exhibits perfect adherence to the substrate. The distribution of elements is homogeneous through the depth of the (AlCrNbSiTiV)N film, as measured by an auger electron nanoscope. After interrupted turning with an (AlCrNbSiTiV)N film coated tool, we obtain much longer tool life than when using uncoated tools. The correlation of these results with microstructure analysis and tool life indicates that HIPIMS discharge induced a higher (AlCrNbSiTiV)N film density, a smoother surface structure and a higher hardness surface.

Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (1018 cm−2): Their structure and mechanical properties

Multielement high entropy alloy (HEA) nitride (TiHfZrNbVTa)N coatings were deposited by vacuum arc and their structural and mechanical stability after implantation of high doses of N+ ions, 1018cm−2, were investigated. The crystal structure and phase composition were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy, while depth-resolved nanoindentation tests were used to determine the evolution of hardness and elastic modulus along the implantation depth. XRD patterns show that coatings exhibit a main phase with fcc structure, which preferred orientation varies from (111) to (200), depending on the deposition conditions. First-principles calculations reveal that the presence of Nb atoms could favor the formation of solid solution with fcc structure in multielement HEA nitride. TEM results showed that amorphous and nanostructured phases were formed in the implanted coating sub-surface layer (∼100nm depth). Concentration of nitrogen reached 90at% in the near-surface layer after implantation, and decreased at higher depth. Nanohardness of the as-deposited coatings varied from 27 to 38GPa depending on the deposition conditions. Ion implantation led to a significant decrease of the nanohardness to 12GPa in the implanted region, while it reaches 24GPa at larger depths. However, the H/E ratio is ⩾0.1 in the sub-surface layer due to N+ implantation, which is expected to have beneficial effect on the wear properties.

Effect of sputtering parameters on (AlCrMnMoNiZr)N films

To optimise the performance of high entropy alloy nitride films, (AlCrMnMoNiZr)N films were deposited through reactive radio frequency magnetron sputtering at a certain N2/Ar flow ratios of 0·5. The effects of sputtering power and substrate temperature on the structure and properties of the films were investigated. Results showed that sputtering power had strong effects on the phase transformation from amorphous to face centred cubic solid solution structure with (200) preferred orientation. The films with coarsened grains had a higher hardness at high substrate temperature because of the inverse Hall–Petch effect. When the sputtering parameters were set at 250 W and 600 K, high hardness of 15–18 GPa and low friction coefficient of 0·12∼0·15 can be obtained. Therefore, the optimised parameters are 250 W and 600 K.

Structure and properties of two Al–Cr–Nb–Si–Ti high-entropy nitride coatings

Two high-entropy alloy nitride films, (Al23.1Cr30.8Nb7.7Si7.7Ti30.7)N50 and (Al29.1Cr30.8Nb11.2Si7.7Ti21.2)N50, were designed and prepared by reactive magnetron sputtering. The influences of substrate bias (from −50V to −150V) on chemical composition, microstructure, and mechanical properties of the deposited films were investigated. All the films have face-centered cubic NaCl-type structure. The (Al23.1Cr30.8Nb7.7Si7.7Ti30.7)Nx films deposited at −100V exhibit the highest hardness of 36.1GPa, and the (Al29.1Cr30.8Nb11.2Si7.7Ti21.2)Nx films have its maximum hardness of 36.7GPa at a substrate bias of −150V. Both (Al23.1Cr30.8Nb7.7Si7.7Ti30.7)Nx and (Al29.1Cr30.8Nb11.2Si7.7Ti21.2)Nx films have outstanding oxidation resistance at 900°C.

Thermally stable amorphous (AlMoNbSiTaTiVZr)50N50 nitride film as diffusion barrier in copper metallization

Results on copper metallization diffusion barriers using high-entropy alloy (HEA) nitride are reported. The HEA nitride (AlMoNbSiTaTiVZr)50N50 is amorphous in the as-deposited state and remains its noncrystallinity up to a high temperature of 850°C. To evaluate its diffusion barrier characteristics, Cu∕(AlMoNbSiTaTiVZr)50N50∕Si test structures were prepared and annealed under 750–900°C for 30min. The results show that the current nitride prevents the reaction between Cu and Si before its failure at 900°C. The outstanding barrier performance and high thermal stability of amorphous structure are suggested to originate from multiprincipal-element effects.