Search

In order to explore effect of V contents on microstructure and tribological properties of AlCrTiNbVxN films, the AlCrTiNbVxN films were deposited on 304 stainless steel by magnetron sputtering system. The structure of films was observed by X-ray diffraction (XRD), scanning electron microscope (SEM). The mechanical properties and tribological properties of films were analyzed by nanoindenter and material surface comprehensive tester. The results show that the AlCrTiNbVxN films show face-cubic structure and have preferred orientation of (200) plane. The diffraction angles shift to right. The AlCrTiNbV1.0N film has the biggest diffraction angle and the smallest interplanar spacing. With the increasing of V contents, the hardness and elastic modulus of films firstly increase and then decrease, and the friction coefficients of films and the width of wear tracks firstly decrease and then increase. The AlCrTiNbV1.0N film has the biggest hardness and elastic modulus. The AlCrTiNbV1.0N film exhibits the best tribological properties with the minimum friction coefficient and the minimum width of the wear track. The wear mechanisms are abrasive wear, adhesive wear, and oxidative wear. [ABSTRACT FROM AUTHOR]

Random delays in the communication links affect the precise tracking of the expected trajectory by a plant controlled by the iterative learning control (ILC) strategy. To tackle the link impact, this paper proposes a state estimator to derive accurate plant outputs that are necessary for controller learning. First, a data pre-processing method is designed to ensure that both the controller and actuator ends receive only one piece of data at any given moment. Subsequently, the data pre-processing method and the system information are used according to the theory of orthogonality to construct the state estimator. The simulation examples demonstrate that the developed estimators aid in the precise tracking of the desired trajectory by the plant implementing ILC strategies through delay links. [ABSTRACT FROM AUTHOR]

Titanium alloys are difficult to machine and have poor tribological properties. Nanoparticles have good cooling and lubricating properties, which can be used in metal cutting fluid. The lubrication characteristics of the two-dimensional materials Ti3C2TX MXene and graphene oxide in water-based fluid for titanium alloys were comparatively investigated in this paper. Graphene oxide had smaller friction coefficients and wear volume than Ti3C2TX MXene nanofluid. As to the mechanism, MXene easily formed TiO2 for the tribo-chemical reaction, which accelerated wear. Moreover, GO nanofluid can form a more uniform and stable friction layer between the frictional interface, which reduces the friction coefficient and decreases the adhesive wear. The effects of different surfactants on the lubricating properties of MXene were further investigated. It was found that the cationic surfactant Hexadecyl trimethyl ammonium chloride (1631) had the lowest friction coefficient and anti-wear properties for the strong electrostatic attraction with MXene nanoparticles. The results of this study indicate that 2D nanoparticles, especially graphene oxide, could improve the lubricating properties of titanium alloys. It provides insight into the application of water-based nanofluids for difficult-to-machine materials to enhance surface quality and cutting efficiency. The developed nanofluid, which can lubricate titanium alloys, effectively has very broad applications in prospect. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of Co contents on the structure and cavitation erosion property, NiTiAlCrCoxN films were prepared by the magnetron sputtering system. The X-ray diffractometer (XRD), the scanning electron microscope (SEM) and the energy dispersive spectrometer (EDS) were used to characterize the structure and morphology of the films. The nanoindenter and the scratch tester were used to analyze the mechanical properties of the films. Cavitation erosion experiments were carried out by the ultrasonic vibration cavitation machine. The results show that NiTiAlCrCoxN films with different Co contents have a simple face-centered cubic (FCC) structure and show a preferred orientation on the (200) crystal plane. The diffraction angle on the (200) crystal plane decreases and the interplanar spacing increases with the increase in Co content in NiTiAlCrCoxN films. NiTiAlCrCoxN films exhibit a typical columnar crystalline structure. With the increase in Co content, the nanohardness of the films increases and the elastic modulus of the films decreases, while the mass loss of cavitation erosion monotonously increases except for the film with a 1.2 Co molar ratio. The NiTiAlCrCo1.4N film has a minimum hardness of 13.264 GPa, a maximum elastic modulus of 253.22 GPa and a minimum mass loss of 0.72 mg in the cavitation erosion experiment. The NiTiAlCrCo1.4N film exhibits the best cavitation corrosion resistance because the addition of the Co element enhances the solid solution strengthening effect and the NiTiAlCrCox1.4N film with the biggest elastic modulus has better elasticity to reduce the micro jet impact. [ABSTRACT FROM AUTHOR]

Titanium alloys are difficult to machine and have poor tribological properties. This paper investigates the lubricating performance of γ-Al2O3/ZnO hybrid nanofluids for Ti-6Al-4V. Pure and hybrid nanofluids are compared, and the effects of γ-Al2O3/ZnO ratios are studied. The results show that γ-Al2O3/ZnO hybrid nanofluids outperform pure nanofluids in terms of lower friction coefficients and better surface quality. Moreover, the hybrid nanofluid with a mass ratio of Al2O3 to ZnO of 2:1 demonstrates the best lubrication performance with a reduced friction coefficient of up to 22.1% compared to the base solution, resulting in improved surface quality. Al2O3 nanoparticles can adhere to the surface of ZnO nanoparticles and work as a coating, which further enhances the lubrication performance of the water-based nanofluid. [ABSTRACT FROM AUTHOR]

Exploring the lubricity characters in van der Waals (vdW) interfaces is a hot topic in nanotribology. We study the friction performances for the Ohmic-contacted lattice-matched SnS2/NbTe2 and lattice-mismatched SnS2/graphene vdW systems through DFT simulations. The friction in the lattice-mismatched system is found to be two orders of magnitudes smaller. The weaker interaction between the interface and the smoother condition at the interface in the SnS2/graphene system leads to a smoother potential energy fluctuation, which is responsible for the tiny friction in compared to the SnS2/NbTe2 system. Moreover, the friction coefficients are quite low for the lattice-mismatched bilayer with values of 5.16 × 10–3–6.46 × 10–2 under a load of 3.46 × 10–3 ~ 0.15 nN/atom. Our work suggests the SnS2/graphene vdW system is a potential solid lubricant with superlubricity. The lattice-mismatched SnS2/graphene vdW system guarantees a distinctly low friction feature due to the tiny variation of charge density difference [ABSTRACT FROM AUTHOR]

The existence mode of Y is an important factor affecting the oxidation resistance of NiCrAlY coating. The traditional thermal sprayed NiCrAlY coating had some problems such as internal-stress-induced coating peeling, when it was used at high temperature for a long time. In this paper, Y-modified NiCrAlY coatings were prepared on the surface of thermal-sprayed NiCrAlY coatings by halide-activated pack-cementation technology. The microstructure and oxidation resistance of the coatings after thermal insulation at 1100 °C for 100 h were analyzed. The results show that the oxidation resistance of Y-modified NiCrAlY coatings was improved significantly. When the oxidation temperature and time were 1100 °C and 100 h, the oxidation weight gain of thermal sprayed NiCrAl0.5Y and NiCrAl1.0Y coatings was 3.8 and 2.2 times that of Y-modified coatings, respectively. In addition, the NiCrAlY coatings prepared by pack cementation had better oxidation resistance than thermal sprayed coatings when the content of Y was equal. The oxidation resistance of the pack-cemented NiCrAlY coatings were increased with the increase in Y content when it was in a range of 0~1 wt.%. When oxidized at 1100 °C for 100 h, the oxidation weight gain of the pack-cemented NiCrAl0.5Y and NiCrAl1.0Y coatings was about 1.8 and 0.9 mg/cm2, respectively. The formation of highly stable intermetallic compounds Ni5Y in the pack-cemented Y-modified coatings is concluded to be the reason for improving the oxidation resistance of the coatings. This work can provide a solution to improve the oxidation resistance of traditional MCrAlY coatings. [ABSTRACT FROM AUTHOR]