Search

Diamond-like carbon (DLC) coatings enhance tool wear resistance across various temperatures. The sp3/sp2 bond ratio within DLC significantly impacts its properties and thermal stability. Elevated temperatures can alter DLC's structure, while metallic elements and interlayers like chromium can modify its microstructure and performance. To evaluate the potential of W-DLC coatings with a chromium interlayer on 40CrMoV5-1 hot work tool steel under elevated temperatures, mechanical and tribological properties were assessed at room temperature and at temperatures of 100, 200, 300, 400, and 500 °C. Nanoindentation revealed a maximum hardness of 14.1 ± 1.3 GPa for the coating deposited at room temperature, attributed to a high sp3 content confirmed by Raman spectroscopy. Hardness decreased to 9.3 ± 1.0 GPa at 400 °C due to graphitization. The elastic modulus remained relatively constant across all temperatures. Tribological tests indicated a low coefficient of friction (CoF) of 0.15 at room temperature, increasing to 0.35 at 100 °C. The CoF further rose to 0.5 at 200 °C, coinciding with increased graphitization. However, the CoF reduced to 0.45 and 0.35 at 400 °C and 500 °C, respectively, likely due to the formation of a WO3 tribo-film and the protective effect of the chromium interlayer. [ABSTRACT FROM AUTHOR]

In this study, a high entropy composite coating was synthesized by oxidizing a high entropy alloy, AlCrFeCoNi, at elevated temperatures in a pure oxygen atmosphere. X-Ray diffraction (XRD) analysis revealed that the prepared material was a dual-phase composite material consisting of a spinel-structured high entropy oxide and a metallic phase with a face-centered cubic structure. The metallic phase can improve the electrical conductivity of the oxide phase, resulting in improved electrochemical performance. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis unveiled the compositional homogeneity of the composite material. The prepared material was utilized as an anode active material in lithium-ion batteries. Cyclic voltammetry (CV) revealed the oxidation and reduction regions, while the electrochemical impedance spectroscopy (EIS) measurements showed a decrease in the charge transfer resistance during the cycling process. A long-term rate capability test was conducted at various current densities: 100, 200, 500, 1000, and 2000 mA g−1. During this test, a notable phenomenon was observed in the regeneration process, where the capacity approached the initial discharge capacity. Remarkably, a high regeneration efficiency of 98% was achieved compared with the initial discharge capacity. This phenomenon is typically observed in composite nanomaterials. At a medium current density of 500 mA g−1, an incredible discharge capacity of 543 mAh g−1 was obtained after 1000 cycles. Based on the results, the prepared material shows great potential for use as an anode active material in lithium-ion batteries. [ABSTRACT FROM AUTHOR]