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Abstract Coating oxidation performance is a major concern in modern machining and other high temperature applications. This study presents TiAlCrN composite coatings with different Cr content prepared on a magnetron sputtering device. SEM, AFM and XRD were used to determine the structure of the coatings. It was found that the coatings show a solid solution of B1-NaCl face-centered cubic structure with [200] preferential orientation. As the Cr content increases, the particle size and roughness of the coating increase slightly, while the hardness of the coating decreases. Oxidation tests revealed that no significant oxidation occurs in all coatings below 800 °C. However, as the oxidation temperature increases to 1000 °C, the Ti 0.32 Al 0.38 Cr 0.30 N coating undergoes severe oxidation and the Ti 0.17 Al 0.19 Cr 0.64 N coating remains good. The oxide scale of the coatings after oxidation test is analysis by XPS depth profiling in details. XPS results revealed that the oxide scale of the Ti 0.32 Al 0.38 Cr 0.30 N coating changes from a dense Al rich oxide layer (800 °C) to a loose and discontinuous Ti Al rich oxide layer (1000 °C), which is the main reason for its poor oxidation resistance. However, the Ti 0.17 Al 0.19 Cr 0.64 N coating shows a top loose Ti Al rich oxide layer and a dense bottom Cr Al rich oxide layer. The presence of this dense and continuous Cr Al rich oxide layer can limit the rapid diffusion of Ti atoms to the surface while preventing the oxygen atoms from diffusing into the interior, which is the key to excellent oxidation resistance of the Ti 0.17 Al 0.19 Cr 0.64 N coatings. Highlights • The oxide scale of TiAlCrN coating was characterized by XPS depth profiling. • As the chromium content increases, the oxidation resistance of the TiAlCrN coating increases. • The excellent oxidation resistance strongly depended on the compact Cr Al rich oxide layer. • The presence of the Cr Al rich oxide layer can limit the rapid diffusion of Ti atoms to the surface. [ABSTRACT FROM AUTHOR]

The Mo x N coatings are deposited by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). It is found that the Mo x N coatings prepared by HiPIMS has a denser microstructure, higher hardness and wear resistance. Besides, the effect of peak current is investigated with respect to the microstructure, mechanical properties and tribological behavior of the coatings. As the peak current increases, the cross-sectional morphology of the coating transforms from featureless to columnar morphology, and the preferred orientation of the coating gradually transfers from (111) to (200). However, the hardness of the coating is not significantly influenced by the peak current. The Mo x N coating with a peak current of 260 A owns a low friction coefficient of 0.28, which is better than that of the Mo x N coating prepared by DCMS. The Mo x N coating with a peak current of 300 A provides excellent wear resistance with the lowest wear rate of 5 × 10−8 mm3/(Nm). [ABSTRACT FROM AUTHOR]

High surface quality coatings play an important role in producing high precision coating tools for micromachining. This study focuses on the improvement of the coating surface quality by layered design method. The layered TiAlTaN/Ta coatings have been prepared by magnetron sputtering. SEM and AFM results revealed that the continuous growth of the columnar TiAlTaN crystals can be interrupted by layered design. The columnar crystal size of TiAlTaN coating decreased with the decreasing bilayer thickness. The coating surface roughness also gradually decreased from 36.6 ± 1.2 to 11.54 ± 0.6 to 8.9 ± 0.1 nm. Nanoidentation results showed an increasing coating hardness from 16 GPa to 20 GPa with decreasing bilayer thickness. Friction and wear test revealed that the coating friction coefficient increases from 0.70 to 0.93, then decreases to 0.62 with decreasing bilayer thickness. The layered method can improve mechanical and friction properties, meanwhile reducing surface roughness, which makes it a potentially promising method for fabricating high precision micromachining coating tools. [ABSTRACT FROM AUTHOR]

Ti 1 − x − y Al x Ta y N coatings with various Ta contents ( y = 0.00–0.37) have been prepared by magnetron sputtering. Scanning electronic microscopy results show that the increased Ta content makes Ti 1 − x − y Al x Ta y N coatings more compact and exhibit a finer columnar structure. X-ray diffraction results show that the preferred orientation of Ti 1 − x − y Al x Ta y N coatings changes from (111) to (200) with increasing Ta content. Nanoindention results indicate that the hardness of the coatings sharply increases from 11 GPa without Ta to 31.2 GPa at y = 0.21. Solution strengthening caused by doping Ta is the main reason for the rapid increase of hardness. After oxidation in ambient air, Ti 0·44 Al 0.56 N coating is fully oxidized to α-TiO 2 and γ-TiO 2 at 600 °C. A significant increase of oxidation resistance for Ti 0·37 Al 0.42 Ta 0.21 N coating has been observed at 800 °C. However, a higher Ta content ( y = 0.37) is not conducive to retard the formation of α-TiO 2 phase at low temperature, but will increase lattice distortion. This can make the coating easy to spall during further oxidation. [ABSTRACT FROM AUTHOR]

Research on the relationship of microstructure and properties of coated tools such as TiAlN and TiAlSiN plays a key role in obtaining the needed cutting performance in titanium machining. In this study, three kinds of coatings of TiAlN, TiAlSiN monolayer and TiAlN/TiAlSiN composite multilayer have been fabricated by magnetron sputtering method. It is found that the coating structure changes from columnar growth to nanocrystal growth by doping Si element. The TiAlN/TiAlSiN coating is composed by a coarse columnar TiAlN bottom layer and a fine nanocrystalline TiAlSiN top layer. Premature spalling problem (Lc2) is improved by forming the TiAlN/TiAlSiN multilayer structure. Titanium cutting experiment shows that the major wear mechanism of these coated tools is adhesive wear and chipping. The TiAlSiN coated tool has the longest cutting distance at various cutting speeds in these three kinds of coatings. This is because less built-up edge and chipping are generated at the cutting edge due to the dense nanocrystal structure, high hardness and good oxidation resistance of TiAlSiN coating. Therefore, the TiAlSiN coating with dense structure, high hardness and good oxidation resistance is recommended to use in high speed turning titanium. [ABSTRACT FROM AUTHOR]

a-C:H films were produced on 316 L stainless steel via magnetron sputtering technique. The effects of bias voltage on the composition, structure and properties of the films were studied. The sp2C fraction grows as the bias voltage increases, and the internal stress and hardness increase constantly. In ambient air, the films deposited at − 150 V have the lowest friction coefficient (COF) of 0.095, while those at − 30 V have the lowest COF of 0.028 in salt solution, benefiting from the higher H content. The corrosion resistance of the film is affected comprehensively by the thickness, surface morphology, sp2 clusters and transition layer. The a-C:H film at − 60 V has the lowest corrosion current density (5.41 ×10−11 A/cm2) and the highest protection efficiency (99.8 %). • The microstructure and composition of the a-C:H films were tailored by the bias. • The lowest friction coefficient in ambient air was 0.095 at the bias of − 150 V. • The lowest average friction coefficient in saline environment was 0.028 at − 30 V. • The anti-corrosion protection efficiency of the 316 L substrate achieved 99.8 % at − 60 V. [ABSTRACT FROM AUTHOR]

High-entropy carbonitrides exhibit excellent properties in friction and corrosion. Here, the tribo-corrosion response of (CrNbTiAlV)C x N y coating were studied in 3.5 wt.% NaCl solution at room temperature. The doping of carbon makes the coating structure dense. When the carbon content of the coating is 40%, the coating exhibits maximum hardness (20.21 GPa). As the carbon content increases, the synergistic effect of tribo-corrosion on the coating gradually weakens, and friction coefficient decreases. The coating with 40% carbon content has the smallest change in static and dynamic current density (0.14 ×10−8 A/cm2), the smallest friction coefficient (0.28), and the smallest wear volume loss. These results show that the coating can effectively protect the substrate in case of tribo-corrosion. [ABSTRACT FROM AUTHOR]

(CrNbTiAlVMo) x N 1−x coatings were deposited on 316 L steel by sputtering method. The structure, mechanical and tribo-corrosion performances of the coating were studied. The results show that all coatings exhibit single FCC structure. With the increase of Mo content, the surface particle size increases, and the orientation changes from (111) to (200). The maximum hardness reaches 44.3 GPa and the corresponding elastic modulus is 405 GPa. Tribo-corrosion test show that the coatings exhibit better resistance to tribo-corrosion than 316 L steel. The coating with 8 at% Mo content has the lowest static current density (7.49 ×10−9 A/cm2) and dynamic current density (9.33 ×10−8 A/cm2), while the coating with 32 at% Mo content shows the smallest wear volume. The related synergistic mechanism of tribo-corrosion was discussed. • The (CrNbTiAlVMo)xN1-x coatings with different Mo contents were prepared by magnetron sputtering. • When the Mo content is 8%, the coating exhibits the highest hardness (44.3 GPa) and elastic modulus (405 GPa). • The (CrNbTiAlVMo)xN1-x coatings exhibit better resistance to tribo-corrosion than 316 L steel. [ABSTRACT FROM AUTHOR]

The (CrAlTiNbV)N x coatings are fabricated by controlling the substrate bias via magnetron sputtering method. Under low substrate bias, the coating tends to form a loose columnar crystal structure with (200) preferred orientation. However, when the substrate bias increases, the coating transforms into a dense nanocrystalline structure, and the (111) orientation is enhanced. As the substrate bias increases, the residual stress and hardness of the coating gradually increase, while the adhesion strength decreases slightly. Friction tests show that the coating possesses the lowest average friction coefficient (about 0.06) and wear rate (8.7 × 10-9 mm3/N·m) in 4050# aviation lubricant, which is achieved under the substrate bias of -96 V and -126 V, respectively. [ABSTRACT FROM AUTHOR]

High temperature coatings possess great potential for improving operation temperature of 4th generation nuclear reactor. In this paper, a high-entropy alloy nitride coatings (CrAlTiNbV)N x were investigated for the application in corrosive lead-bismuth alloy (LBE). The coatings were synthesized by unbalanced magnetron sputtering on ferritic/martensitic (F/M) steel. Properties of (CrAlTiNbV)N x are systematically investigated from perspective of the electron structure, crystalline, and mechanical properties under different bias voltage applied on samples. Significant improvement of hardness (30 GPa) is obtained at bias voltage of -156 V. Furthermore, the corrosion behavior in 550 °C lead bismuth eutectic (LBE) was conducted for 1200 h with saturated oxygen content, which demonstrates the dense structure of coatings with no obvious crack, spallation that characterized by the SEM, EDS, and TEM. Upon the application of high bias voltage, more prone formation of high-density grain boundary with fine grains extends the diffusion path of Pb and Bi are achieved for excellent LBE corrosion resistance. Our work not only provide an insight to the electron structure of high entropy alloy nitrides, but also shows a potential application for (CrAlTiNbV)N x protecting fuel cladding in the next generation lead based reactor. [ABSTRACT FROM AUTHOR]

(CrNbTiAlV)N x high-entropy nitride films were prepared using magnetron sputtering method. The effect of substrate bias on the microstructure, mechanical, electrochemical, and tribo-corrosion properties of the films was systematically studied. The results show that the microstructure of the film changes from a loose columnar structure to a compact nanocrystal structure with the increase of substrate bias, accompanied by the preferred orientation from (200) to (111). The hardness, modulus and residual stress are positively correlated with increased substrate bias, reaching the maximum values of 35.3 GPa, 353.7 GPa and −6.41 GPa at −156 V, respectively. Under static corrosion, the film deposited under −126 V has the most positive E corr of −0.05 V and the lowest i corr of 0.013 μA/cm2. Under tribo-corrosion, the films deposited at −96 V and −126 V show the lowest coefficient of friction (~0.2) and wear rate (~4.4 × 10−7 mm3·N−1·m−1), respectively. The evolution of microstructure and mechanical property are the main factors affecting the tribo-corrosion behavior of (CrNbTiAlV)N x films. [Display omitted] • (CrNbTiAlV)N x high-entropy films were deposited at various substrate bias by magnetron sputtering. • The structure of the films changed from loose columnar to compact with the increase of substrate bias. • The hardness, modulus and residual stress of the films were positively correlated with increasing bias. • The influencing factors of (CrNbTiAlV)N x films under static corrosion and dynamic tribocorrosion were discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The (CrAlTiNbV)N x high-entropy coatings are prepared by magnetron sputtering method. • All coatings exhibit columnar growth morphology and own a single FCC structure. • The S-38 owns a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m). • The excellent wear resistance of S-38 is mainly attributed to its dense structure. (CrAlTiNbV)N x high-entropy nitride coatings are deposited via tuning nitrogen flow rates, and evaluating their influence on the microstructure, mechanical and tribological properties of the coatings. All deposited coatings exhibit columnar growth morphology and own a single face-center-cubic structure. As the nitrogen flow rate increases, the preferred orientation of the coating gradually transfers from (1 1 1) to (2 0 0) and (2 2 0), and then changes back to (1 1 1) with the nitrogen flow rate continues to increase. The S-38 sample possesses the optimal plastic deformation resistance and adhesion strength. Friction and wear results show that the (CrAlTiNbV)N x coating deposited at nitrogen flow rate of 38 sccm owns the best tribological properties with a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m) in 4050# aviation oil. [ABSTRACT FROM AUTHOR]