Surface texture is regarded as a promising solution for enhancing the tribological features of industrial materials due to its outstanding benefits, such as minimization of the contact area, enhancement of the load bearing capacity, storage of the lubricant, and management of the transition between lubrication regimes. Surface texture can be processed under either liquid or gas conditions. As compared to laser ablation in air, employing liquids or other gases as ablation media provides high accuracy and uniformity by limiting the heat-affected zone (HAZ) and other undesired defects to a large extent, as well as high crater structural features. In addition, the synergistic use of different liquid, solid, and additive lubricants with surface roughness recently demonstrated excellent performance. Therefore, surface texture helps to improve the tribological characteristics of a material. This paper reviews the design methodologies and applications of surface texture, emphasizing the proper selection of the appropriate laser parameters and ambient conditions for the best texture quality and functionality. Recent texture geometric design features to improve the film thickness and the self-lubricating system are presented. The ablation environment is explored using various media. The interaction between the lubricants’ types and surface textures is explored based on the operating conditions. Furthermore, surface texture applications using superhydrophobic surfaces, anti-drag, and vibration and noise friction are discussed. We hope that this review plays an enlightening role in follow-up research on laser surface texture.

The achievement of a superlubricity state with vanishing friction and negligible wear has important applications in minimizing energy dissipation and prolonging the service life of moving mechanical systems. However, the search for a superlubricious oil system applicable to industrial fields remains a big challenge. We demonstrate in this work for the first time that precisely employing polyether modification for silicone oil molecules could induce direct superlubricity and superlow wear for engineering steel tribopairs. Superlubricity originates as the polyether-modified silicone oil could effectively employ the polyether functional group to interact with the friction surfaces, during which a complex tribochemical reaction process could be induced under the catalytic role of friction, where an organic lubricious film mainly composed of carbon, silicon and oxygen elements could be induced to be in-situ formed, which could not only effectively passivate the friction surfaces but also enable the superlubric sliding by virtue of its easy-to-shear nature. Furthermore, iron oxides and chromium oxides could also be confirmed distributed within the tribofilm, desirable for increasing the load-bearing capability of tribofilm and the toughness. Thus, remarkable superlubricity of 0.01 without a running-in combined with superlow wear has been realized at the same time. The results of this work show high promise in promoting the industrial use of oil superlubricity and revolutionizing the development of mechanical systems.

Friction remains as the primary mode of energy dissipation and components wear, and achieving superlubricity shows high promise in energy conservation and lifetime wear protection. The results in this work demonstrate that direct superlubricity combined with superlow wear can be realized for steel/Si₃N₄ contacts on engineering scale when polyhydroxy alcohol solution was selectively modified by amino group. Macroscopic direct superlubricity occurs because 3-amino-1,2-propanediol molecules at the friction interface could be induced to rotate and adsorb vertically on the friction surface, forming in-situ thick and dense molecular films to passivate the asperity contacts. Furthermore, amino modification is also conducive to improving the lubrication state from boundary to mixed lubrication regime by strengthening the intermolecular hydrogen bonding interaction, presenting enhanced load-bearing capability and reduced direct solid asperity contacts. Thus, direct superlow average friction of 0.01 combined with superlow wear are achieved simultaneously. The design principle of direct superlubricity and superlow wear in this work indeed offers an effective strategy to fundamentally improve energy efficiency and provide lifetime wear protection for moving mechanical assemblies.

Achieving robust and reliable ultra- to super-low friction combined with extremely low wear, which is applicable to industrial applications, has always been the pursuit of researchers. In this work, carboxylated graphene quantum dots (CGQDs) were synthesized for dissolution into polyether-modified silicone oil (PESO). The results indicate that CGQDs demonstrate exceptional solubility in PESO, which can be attributed to the favorable charge–transfer interaction between CGQDs and PESO molecules. Tribological tests indicate that the addition of CGQDs to PESO could result in a robust and reliable superior lubrication effect for steel tribopairs under a wide range of testing conditions, with the lowest friction coefficient being approximately 0.02. The investigation of the wear scars indicates that CGQDs can effectively embed into friction contacts due to their ultrasmall size, allowing them to interact effectively with the steel surface through their carboxy groups and therefore forming an in-situ robust CGQDs-based lubricant film. The generated CGQDs-based lubricant film could not only effectively passivate the direct asperity contacts of tribopairs but also provide a shearable path due to its desirable lamellar characteristics. The findings of this work are expected to provide a novel reliable strategy to achieve ultra- to super-lubrication for industrial applications.