Tribological Behavior and Mechanism of Plasma-Sprayed High-Entropy Monoboride Coating over a Wide Temperature Range

Due to the extremely high hardness of high-entropy monoborides (HEMB), this study successfully prepared a new type of HEMB-(V0.2Cr0.2Ta0.2Mo0.2W0.2)B coating by adjusting the spraying process using atmospheric plasma spraying technology. The high-entropy coating was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The change rule concerning the alteration in the phase composition of the coating surface with power and protective atmosphere was explored, indicating that with the decrease in power and the application of a protective atmosphere, the generation of oxide on the coating surface is successfully inhibited. The wear resistance of the coating in a temperature range from room temperature to 800 °C was evaluated in dry sliding wear test conditions. The results indicated that the wear mechanism of (V0.2Cr0.2Ta0.2Mo0.2W0.2)B coating below 400 °C is abrasive wear, and above 400 °C, the wear mechanism is mainly oxidative wear.