This study explores the impact of substrate hardness on the tribological properties of graphene oxide (GO) solid lubricant coatings on NiP alloy layers coated Q235 steel. Through the adjustment of electroless plating parameters, NiP alloy layers with varying hardness levels were produced to investigate their effect on the wear resistance and friction performance of GO coatings. The methodology included substrate preparation, electroless NiP alloy plating, electrophoresis deposition of GO, and detailed analysis of the structural, mechanical, and tribological characteristics of the coatings. The findings underscore the crucial role of substrate hardness in the tribological efficiency of GO coatings. A specific hardness level emerged as optimal, significantly enhancing the distribution and effectiveness of the GO tribofilm. This uniform and continuous tribofilm presence led to notable improvements in wear resistance and a reduction in friction coefficients. Moreover, this optimal hardness ensured continuous lubrication and superior load-bearing capabilities, substantially prolonging the lifespan of the coatings. The substrates with either too high or too low hardness levels were observed to hinder the maintenance of a consistent tribofilm, thereby negatively impacting the tribological performance of the coating. Conclusively, this research highlights the significance of achieving an optimal substrate hardness to enhance the tribological performance of solid lubricant coatings. By optimizing the balance between substrate hardness and the integrity of the tribofilm, the study paves the way for developing more efficient, durable, and environmentally sustainable mechanical components, offering new insights into tribological science and materials engineering.

The outstanding tribological performance of transition metal dichalcogenides (TMDs) is attributed to their unique sandwich microstructure and low interlayer shear stress. This advantageous structure allows TMDs to demonstrate exceptional friction reduction properties. Furthermore, the incorporation of TMDs and amorphous carbon (a-C) in multi-layer structures shows excellent potential for further enhancing tribological and anti-oxidation properties. Amorphous carbon, known for its high ductility, chemical inertness, and excellent wear resistance, significantly contributes to the overall performance of these multi-layer coatings. To gain an in-depth understanding of the tribological mechanism and evolution of TMDs’ multi-layer coatings, a dual in-situ analysis was carried out using a tribometer equipped with a 3D laser microscope and a Raman spectrometer. This innovative approach allowed for a comprehensive evolution of the tribological, topographical, and tribochemical characteristics of both single-layer WS₂ and multi-layer WS₂/C coatings in real time. The findings from the dual in-situ tribotest revealed distinct failure characteristics between the single-layer WS₂ coating and the multi-layer WS₂/C coating. The single-layer WS₂ coating predominantly experienced failure due to mechanical removal, whereas a combination of mechanical removal and tribochemistry primarily influenced the failure of the multi-layer WS₂/C coating. The tribological evolution process of these two coatings can be classified into four stages on the basis of their tribological behavior: the running-in stage, stable friction stage, re-deposition stage, and lubrication failure stage. Each stage represents a distinct phase in the tribological behavior of the coatings and contributes to our understanding of their behavior during sliding.

A one-step method was developed to create a highly biocompatible micropatterned surface on a diamond-like carbon (DLC) through irradiation with a nitrogen ion beam and thus enhance the biocompatibility of osseointegrated surfaces and biotribological performance of articular surfaces. The biocompatibility and biotribological mechanisms were analyzed in terms of the structure and morphology of DLC. It was demonstrated that a layer enriched in sp³ C–N bonds was formed on the surface of the DLC after nitrogen ion beam irradiation. Moreover, with an increase in the radiation dose, the content of sp³ C–N on the DLC surface increased significantly, and the biocompatibility was positively correlated with it. The adhesion of the MC3T3 osteoblasts increased significantly from 32% to 86% under an irradiation dose of 8 × 10¹⁵ ions/cm². In contrast, the micropattern had a significant negative effect on the adhesion of the osteoblasts as it physically hindered cell expansion and extension. The micropattern with a depth of 37 nm exhibited good friction properties, and the coefficient of friction was reduced by 21% at relatively high speeds.