Hao Kang

Bio: Hao Kang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Grain size & Amorphous carbon. The author has an hindex of 1, co-authored 2 publications receiving 4 citations.

Lubricating coating and preparation method thereof

Abstract: The invention relates to a lubricating coating and a preparation method thereof. The lubricating coating is prepared by a direct-current magnetron sputtering method. The lubricating coating comprisesa transition layer and a functional layer, wherein the transition layer is used for attaching to a base body, and the functional layer is attached to the transition layer; the functional layer comprises a plurality of VAlN layers and a plurality of VAlCN layers which are sequentially and alternately arranged, wherein the atomic percentage of V elements to Al elements in each VAlN layer and in eachVAlCN layer is 1:1.5-1:5, the content of N elements in each VAlN layer is 20 at.%-40 at.%, the content of N elements in each VAlCN layer is 10 at.%-30 at.%, the content of C elements is 20 at.%-30 at.%, and the C elements exist in the form of amorphous carbon. According to the lubricating coating, oxidation can be effectively delayed, the action time of a lubricating phase in the lubricating coating is prolonged, and then the service life of the lubricating coating in the high temperature is prolonged.

Ab initio predictions of structure and physical properties of the Zr2GaC and Hf2GaC MAX phases under pressure.

Abstract: The electronic structure, structural stability, mechanical, phonon, and optical properties of Zr2GaC and Hf2GaC MAX phases have been investigated under high pressure using first-principles calculations. Formation enthalpy of competing phases, elastic constants, and phonon calculations revealed that both compounds are thermodynamically, mechanically, and dynamically stable under pressure. The compressibility of Zr2GaC is higher than that of Hf2GaC along the c-axis, and pressure enhanced the resistance to deformation. The electronic structure calculations reveal that M2GaC is metallic in nature, and the metallicity of Zr2GaC increased more than that of Hf2GaC at higher pressure. The mechanical properties, including elastic constants, elastic moduli, Vickers hardness, Poisson’s ratio anisotropy index, and Debye temperature, are reported with fundamental insights. The elastic constants C11 and C33 increase rapidly compared with other elastic constants with an increase in pressure, and the elastic anisotropy of Hf2GaC is higher than that of the Zr2GaC. The optical properties revealed that Zr2GaC and Hf2GaC MAX phases are suitable for optoelectronic devices in the visible and UV regions and can also be used as a coating material for reducing solar heating at higher pressure up to 50 GPa.

Fabrication and Mechanical Properties of Cr2AlC MAX Phase Coatings on TiBw/Ti6Al4V Composite Prepared by HiPIMS.

Abstract: The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic.