Search

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]

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]

Adhesive wear is one of the major reasons for the failure of components during various tribological application, especially for rubbing with viscous materials. This study presents CrN/DLC/Cr-DLC multilayer composite coatings prepared on a plasma enhanced chemical vapor deposition (PECVD) device with the close field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique. SEM, XRD and Raman spectroscopy were used to determine the structure of multilayer coatings. It was found that the multilayer coatings are composed by the alternating CrN and DLC layers. Compared with the single CrN coatings, the friction coefficient of the CrN/DLC/Cr-DLC multilayer coating decreases about more than seven times after sliding a distance of 500 m. This helps to reduce the adhesive wear of multilayer coatings. Compared with the single CrN and DLC coating, the wear rate of the CrN/DLC/Cr-DLC multilayer coating is reduced by an order of magnitude to 7.10 × 10 −17 (sliding with AISI 440C) and 2.64 × 10 −17 (sliding with TC4) m 3 /(N m). The improved tribological performance of multilayer coatings mainly attributes to the introduction of lubricant DLC and hard support CrN layers, the enhancement of crack propagation inhibition, and the increment of elastic recovery value W e (71.49%) by multilayer design method. [ABSTRACT FROM AUTHOR]

Fracture toughness is an important characteristic for coatings for high speed cutting of titanium. This study focuses on improving the fracture toughness of the coatings using a layered design method. TiAlN/CrN multilayer coatings with bilayer periods between 12 nm and 270 nm were prepared by reactive magnetron sputtering. XRD results show the multilayer coatings have face-centred cubic structures. When the bilayer period of multilayer coating decreases from 270 nm to 25 nm, the coating hardness decreases from 24.5 GPa to 18.1 GPa. Increased fracture toughness and adhesion strength of multilayer coatings are observed with decreasing bilayer periods. A maximum fracture toughness (K IC ) of 3.6 MPa m 1/2 and adhesion strength of 107 N were obtained with a 25 nm bilayer period. The inhibition of crack propagation is the main reason for the high fracture toughness values in multilayer coatings. However, when the bilayer period is decreased further (12 nm), the coating hardness begins to increase rapidly to 23.4 GPa, and the fracture toughness and adhesion strength begin to decrease. Titanium cutting results show that an improvement in cutting performance is obtained with a TiAlN/CrN_25 multilayer coating. [ABSTRACT FROM AUTHOR]

Adhesive wear is one of the major reasons for short tool life during machining titanium alloys. This study presents a new kind of low adhesive wear TaO functional coating prepared by magnetron sputtering. The composite coating is composed by two layers of a solid solution TiAlTaN in bottom and a TaO (Ta 2 O 5 or TaO x ) on top. Tool life of the TiAlTaN/TaO coatings is increased more than triple the TiAlTaN single coating by titanium cutting experiments. Cutting performance of commercial TiAlN-based coated tool is increased 267% after coating the TaO on the surface. Friction and wear between the coatings and Ti6Al4V counterpart have been conducted. The results show that both the friction coefficient of the coatings (from 1.05 to 0.82) and surface roughness (from 12.2 ± 0.6 to 7.1 ± 0.1 nm) are decreased by increasing TaO thickness from 0 to 150 nm. The adhesive bonds between coating and titanium also reduce with increasing the TaO thickness. This leads to the significantly reduction of the adhesion at the cutting tool tip after coated the TaO coating. This is because that the titanium is not easy to bind with the TaO coating by the calculated positive interaction energy between the Ta 2 O 5 surface and pure Ti. [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]

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]

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp2 hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating. [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]

Cr-doped amorphous carbon (a-C:Cr) film is a promising protective coating to extend the lifetime of Co–Cr–Mo implants. Here, a-C:Cr films with the same doping concentration of Cr and thickness are deposited on Co–Cr–Mo substrates using the closed-field unbalanced magnetron sputtering (UBMS) and the plasma-enhanced chemical vapor deposition (PECVD) methods. A comparative study on the microstructure, bio-tribological behavior, and cytocompatibility of two kinds of a-C:Cr films in the air and different simulated body fluids is conducted. Microstructural analysis results show that the a-C:Cr films prepared by UBMS and PECVD methods belong to graphite-like carbon (GLC) and diamond-like carbon (DLC) films, respectively. Nanohardness of the UBMS a-C:Cr film is found to be lower than that of the PECVD counterpart. However, the UBMS a-C:Cr film exhibits better lubrication, lower wear depth and lower wear volume under all the three simulated body fluids, because of the slight polishing wear and boundary lubrication mechanisms. Moreover, both kinds of a-C:Cr films significantly improve the cytocompatibility of Co–Cr–Mo substrate alloy. • Two vapor deposition methods are used to fabricate a-C:Cr films. • Microstructure, bio-tribological properties and cytocompatibility are comparatively studied. • Different deposition methods lead to different microstructures and bio-tribological properties. • The wear mechanisms of both a-C:Cr films in simulated body fluids are the slight polishing. • Both a-C:Cr films can greatly enhance the cytocompatibility of the original CoCrMo substrate. [ABSTRACT FROM AUTHOR]

WS 2 films with different structures and space lubricating oils are combined to construct the WS 2 /oils composite lubricating systems. Friction and wear of the WS 2 /oils systems are mainly studied in vacuum. Results show that WS 2 /P201 systems display much lower friction coefficient (μ ≈ 0.06) than WS 2 /PFPE systems (μ ≈ 0.11), which is found to depend on lubricity of oils. Noteworthily, the dense WS 2 film of the WS 2 /PFPE systems has the lowest wear rate of about 5.6 × 10−6 mm3·(N·m)−1 although friction coefficient of the system is high. This is due to good wettability of PFPE on the dense WS 2 film, whose contact angle is low to 5°. Eventually, the lubricating mechanism of the WS 2 /oil systems are revealed via correlating interaction between oil molecules and WS 2 crystals. [ABSTRACT FROM AUTHOR]

The wear-resistant Ta 4 HfC 5 nanoceramics were prepared via polymer preceramic routes. Tribological behavior of the generated nanoceramics from room temperature to elevated temperatures was investigated. The results shows that the coefficient of friction (COF) of the Ta 4 HfC 5 sliding against Si 3 N 4 first increases and then decreases with the rise of temperature, reaching as low as about 0.20 at 800 °C. The low COF at 800 °C is dominantly ascribed to the formation of oxide tribo-film on the worn surface. The fine microstructure benefiting from the polymer precursor synthesis imposes positive effect to the reduction of friction coefficient at the high temperature. • Ta 4 HfC 5 nanoceramics with fine microstructure was prepared by polymer-derived ceramics (PDCs) route. • The high temperature tribological behavior of the Ta 4 HfC 5 nanoceramics was investigated. • The low friction coefficient of the polymer-derived Ta 4 HfC 5 nanoceramics reached as low as about 0.20 at 800 °C. • The fine microstructure of polymer-derived Ta 4 HfC 5 contributed to the formation of compact oxide tribo-layer at 800 °C. [ABSTRACT FROM AUTHOR]

The high-throughput preparation of MoS 2 -(Cr, Nb, Ti, Al, V) composite coatings was achieved by multi-targets co-sputtering method. Based on the obtained friction coefficient of 236 samples as the criterion, four samples with the largest difference in friction coefficient were screened out for further detailed investigations. The results demonstrated that high metal doping amount can dense the coating and reduce the particle size. As the doping content increased, the coating transformed from nanocrystalline to amorphous structure. Consequently, MoS 2 -(Cr, Nb, Ti, Al, V) composite coatings with high doping levels presented higher hardness and better atmospheric tribological properties. Moreover, the Cr and Al dopants can better inhibit the oxidation of MoS 2 than Nb, Ti and V dopants owing to the denser oxide films. • More than two hundreds of doped MoS 2 coatings are prepared by high throughput preparation. • The coatings with high doping contents own higher hardness and better tribological properties. • As the doping content increases, the coating transform from nanocrystalline to amorphous structure. • The Cr and Al dopants can better inhibit the oxidation of MoS 2 than Nb, Ti and V dopants. • The P8 sample owns a friction coefficient of about 0.03 and wear rate of 3.16 × 10−7 mm3/(N.•m). [ABSTRACT FROM AUTHOR]

Cr-doped graphite-like carbon (Cr-GLC) coatings and Cr-doped diamond-like carbon (Cr-DLC) coatings were prepared by PVD and PECVD, respectively. The lubrication behaviour of the solid-liquid composite lubrication systems was investigated using two ionic liquids (ILs) as lubricants. The results show that the friction coefficient was reduced by approximately 40% compared with that under the dry condition, and the composite system exhibited a good synergistic lubrication effect. The Cr-DLC coating showed better tribological behaviour than the Cr-GLC coating, which can be ascribed to a better physicochemical film formation under friction and the compact microstructure of the Cr-DLC coating. The synergistic effect of the composite systems was affected by the viscosity and corrosiveness of the ILs and the microstructure of the coatings. Image 1 • The Cr-GLC and Cr-DLC coatings were prepared by PVD and PECVD method, respectively. • The friction coefficient decreases from 0.11 (dry condition) to 0.045–0.06 (ILs condition). • The lubrication of solid-liquid systems is mainly affected by the wettability of ionic liquids. • The tribological properties of Cr-GLC in ionic liquids are more affected by the corrosion effect. [ABSTRACT FROM AUTHOR]