Thickness and sp bond modulation of (Ti/tetrahedral amorphous carbon) multilayer coatings

The durability of wear-resistant tetrahedral amorphous carbon (ta-C) coatings is intimately linked to their thickness and the concentration of sp bonds. To enhance the lifespan of the coatings, we have prepared a multilayer coating consisting of alternating layers of Ti and ta-C, denoted as (Ti/ta-C), using arc ion plating. A multi-layer structure in conjunction with stage cooling is employed to enhance the thickness and promote sp bonding. The results indicate that the I/I value, representing the ratio of the intensity of the D peak to that of the G peak in Raman spectroscopy, decreases from 0.85 when no stage cooling is applied to 0.35 when stage cooling is employed, suggesting an enhancement in the fraction of sp bonds within the coating. The obtained (Ti/ta-C) multilayer coating without peeling off has a maximum thickness of 1.14 μm, which is almost double that of the ta-C coating single layer coating. At the same time, the coating has a low coefficient of friction, down to 0.069, and maintains excellent friction properties with a wear rate of 3.4 × 10 mm·N·m. The results conclusively show that the preparation technology can enhance both thickness and sp bonding in ta-C coatings, significantly expanding their utility across tools, molds, and precision engineering components.