Abstract
We report the structure, mechanical properties, thermal stability, and durability of Si/SiC/ta-C composite (Si–ta-C) coatings fabricated using simultaneous filtered cathodic vacuum arc deposition and direct current unbalanced magnetron sputtering. Si concentration of 1.25–6.04 at.% was achieved by increasing the unbalanced magnetron sputtering power from 25 to 175 W. Si addition provided functionality to the coating, such as heat resistance, while retaining the high hardness of ta-C coatings. The Si–ta-C coatings were stable up to 600 °C regardless of the Si content, while the coating containing 3.85 at.% Si was stable up to 700 °C. The friction behavior and mechanical properties were dependent on the coating film before and after annealing at 100–200 °C; however, annealing at 300–400 °C decreased disk wear and increased counterpart wear due to an increase in film hardness on account of an endothermic reaction that increased the number of Si–C bonds. This indicates that the basic hardness characteristics of the ta-C coating and the high-temperature structural change of the Si–ta-C coating are important for ensuring high-temperature durability. These characteristics were verified through the low coefficient of friction and wear rate of the 1.25 at.% Si–ta-C coating after annealing at 500 °C.
Highlights
Diamond-like carbon (DLC) coatings have excellent mechanical and chemical properties and have been applied in many industrial fields
This study provides new insights into improving the thermal stability and tribological properties of Si/SiC/tetrahedral amorphous carbon (ta-C) composite (Si–ta-C) coatings by elucidating the effect of Si co-deposition and annealing on the structure, mechanical properties, heat resistance, and tribological characteristics of ta-C coatings at elevated temperatures
This study established the reliability of DLC coatings upon exposure to high-temperature atmospheric environments after composite with a small amount of Si to improve their thermal degradation and durability while maintaining high mechanical properties
Summary
Diamond-like carbon (DLC) coatings have excellent mechanical and chemical properties and have been applied in many industrial fields. The heat resistance of non-hydrogenated DLC coatings is still too low for moving parts operated in high-temperature environments under external forces. To suppress the endothermic reaction, transition metals such as Si can be introduced into the DLC coating This improves the thermal stability and high-temperature tribological behavior. The mechanical and tribological properties of CVD-based Si-doped DLC coatings deposited using tetramethylsilane (TMS, Si(CH3)4) have been found to decrease at temperatures above ~ 400 °C2. These issues must be addressed; despite interest in high-temperature tribological behavior, few studies have considered methods of preventing the thermal degradation of Si-doped DLC coatings. This study provides new insights into improving the thermal stability and tribological properties of Si/SiC/ta-C composite (Si–ta-C) coatings by elucidating the effect of Si co-deposition and annealing on the structure, mechanical properties, heat resistance, and tribological characteristics of ta-C coatings at elevated temperatures
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