As the hardest known material, diamond and its coatings continue to generate significant attention for stringent applications involving extreme tribological conditions. Likewise, diamond-like carbon (DLC, especially the tetragonal amorphous carbon, ta-C) coatings have also maintained a high level interest for numerous industrial applications where efficiency, performance, and reliability are of great importance. The strong covalent bonding or sp³-hybridizaiton in diamond and ta-C coatings assures high mechanical hardness, stiffness, chemical and thermal stability that make them well-suited for harsh tribological conditions involving high-speeds, loads, and temperatures. In particular, unique chemical and mechanical nature of diamond and ta-C surfaces plays an important role in their unusual friction and wear behaviors. As with all other tribomaterials, both diamond and ta-C coatings strongly interact with the chemical species in their surroundings during sliding and hence produce a chemically passive top surface layer which ultimately determines the extent of friction and wear. Thick micro-crystalline diamond films are most preferred for tooling applications, while thinner nano/ultranano-crysalline diamond films are well-suited for mechanical devices ranging from nano- (such as NEMS) to micro- (MEMS and AFM tips) as well as macro-scale devices including mechanical pump seals. The ta-C coatings have lately become indispensable for a variety of automotive applications and are used in very large volumes in tappets, piston pins, rings, and a variety of gears and bearings, especially in the Asian market. This paper is intended to provide a comprehensive overview of the recent developments in tribology of super-hard diamond and DLC (ta-C) films with a special emphasis on their friction and wear mechanisms that are key to their extraordinary tribological performance under harsh tribological conditions. Based on the results of recent studies, the paper will also attempt to highlight what lies ahead for these films in tribology and other demanding industrial applications.

作为最硬的材料，金刚石及其涂层在涉及极端摩擦条件的严格应用中继续引起人们的极大关注。同样，类金刚石碳（DLC，尤其是四方非晶碳ta-C）涂层对于效率，效率和可靠性至关重要的众多工业应用也保持了很高的关注度。强共价键或sp ³金刚石和ta-C涂层的高杂化可确保较高的机械硬度，刚度，化学和热稳定性，使其非常适合于涉及高速，高负荷和高温的恶劣摩擦条件。特别是，金刚石和ta-C表面的独特化学和机械性质在其异常的摩擦和磨损行为中起着重要的作用。与所有其他摩擦材料一样，金刚石和ta-C涂层在滑动过程中都与周围环境中的化学物质强烈相互作用，因此产生了化学钝化的上表面层，最终决定了摩擦和磨损的程度。厚的微晶金刚石薄膜最适合用于模具应用，而更薄的纳米/超结晶晶体薄膜则非常适合从纳米（例如NEMS）到微米（MEMS和AFM尖端）的机械设备，以及包括机械泵密封的宏观设备。ta-C涂层近来已成为各种汽车应用必不可少的材料，并大量用于挺杆，活塞销，环以及各种齿轮和轴承，尤其是在亚洲市场。本文旨在提供对超硬金刚石和DLC（ta-C）薄膜摩擦学最新进展的全面概述，并特别强调它们的摩擦和磨损机理，这是在苛刻的摩擦条件下其非凡摩擦性能的关键。根据最近的研究结果，