Cr/WC/DLC multilayer films were deposited on GCr15 substrates using a Closed Field Unbalanced Magnetron Sputter Ion Plating-Plasma Enhanced Chemical Vapor Deposition (CFUMSIP-PECVD) technique. The load-dependent tribological behavior and interfacial evolution of the films were systematically investigated under dry sliding, 7014 lubricating grease, and No. 15 aviation hydraulic oil conditions with loads ranging from 200 to 1500N. Under dry sliding, the films maintained stable low friction only at 200N, whereas increasing load caused rapid interfacial degradation involving coating failure, metal exposure, and oxidative wear. In contrast, lubricating grease enabled stable sliding over the entire load range due to the formation of a composite tribofilm consisting of MoS2-derived layered phases and friction-induced graphitized carbon, which enhanced interfacial load-bearing capability. Moreover, graphene nanoscrolls and carbonaceous nanostructures were identified in the wear debris as additional third-body lubricating phases. The tribological behavior under aviation hydraulic oil is highly load-dependent, with the optimal friction and wear performance achieved at 1000N; however, excessive loading at 1500N resulted in boundary lubrication failure and rapid instability. These results demonstrate that the heavy-load reliability of Cr/WC/DLC multilayer films is governed not only by intrinsic mechanical properties but also by the formation and stability of low-shear interfacial layers regulated by lubrication media. This work provides insights into the design of durable DLC-based tribological systems for aviation and heavy-load applications.
Two-dimensional (2D) materials are widely used as lubricating films because of unique layered structure and outstanding physical properties. Low shear resistance in 2D materials benefits ultra-low friction, nevertheless, it is accompanied by easy interlayer slip and therefore poor anti-wear performance. Aiming at this inherent conflict, we developed an interlayer-confined alkyl-cation-intercalation strategy on layered MoS2 bulks. Nanoscale friction and wear tests through atomic force microscopy under dry N2 showed a reduction of friction coefficient by 33% and up to sixfold anti-wear life enhancement via intercalation. Theoretical analysis suggests that the durable lubrication of intercalated MoS2 can be rationalized by strengthened interfacial anchoring associated with greatly enhanced interfacial charge transfer. By coupling the low-friction surfaces and strong inner electron-anchoring among 2D layers, this work demonstrates a nanoscale proof-of-concept pathway for the coexistence of low friction and high wear resistance, offering a promising direction for future design of durable 2D-materials-based lubricating films.
Electroless deposition is a versatile method for fabricating Niₓ–B-based alloy and composite coatings known for superior mechanical and tribological performance across diverse industrial sectors. Using the Nix–B (x = 1, 2, 3…) notation to represent the compositional complexity of these systems, this study compares electroless Nix–B–W alloy and Nix–B–W–hBN composite coatings deposited on low-carbon steel substrates, evaluating hardness, fracture toughness, and coefficient of friction. Particular emphasis is placed on the role of hexagonal boron nitride (hBN) reinforcements as solid lubricants within the Nix‑B‑W matrix (for Nix‑B‑W‑hBN composite coating) and on identifying the key process parameters that enable the hBN‑reinforced composite to outperform the Nix‑B‑W alloy coating. The results show that incorporating hBN particles substantially increases coating hardness and fracture toughness while simultaneously lowering the steady‑state coefficient of friction under the tested load. This study highlights the interplay among bath chemistry, coating microstructure, and tribological response, providing mechanistic insight into the factors that yields the development of a mechanically and tribologically superior coating through hBN incorporation. The rational design of self‑lubricating Nix‑B‑W‑hBN composite coatings demonstrated here holds considerable potential for industrial applications requiring low friction and enhanced wear resistance.
Fish-scale surface mucus exhibits a lubricating effect; however, its specific role in regulating friction and wear during direct solid–solid sliding remains unclear. In this study, crucian carp scales were selected as model biological surfaces. Dried mucus-retained and mucus-removed samples were prepared. Reciprocating sliding tests against a GCr15 steel ball were then conducted in three representative regions. Scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle measurements were used to characterize the surface properties of the two sample groups. Their frictional behavior and wear damage were also compared. The steady-state coefficients of friction in the three regions were reduced from 0.18, 0.59, and 0.62 to 0.16, 0.45, and 0.49, respectively, after mucus retention. These values corresponded to reductions of 11.1%, 23.7%, and 21.0%, respectively. Wear damage was also markedly alleviated. Taken together, the XPS results showed that polar oxygen- and nitrogen-containing organic functional groups were present on the mucus-retained surface. The wettability results further showed that mucus retention increased the hydrophilicity of the fish-scale surface. After sliding, mucus-related residues were retained in the worn regions and were involved in the sliding contact. Direct solid–solid contact between the GCr15 steel ball and the fish-scale substrate was reduced by the residue-mediated interface. The effective interfacial shear resistance was also lowered, resulting in reduced friction and wear. The friction-reducing and wear-protective roles of mucus-derived material retained on the fish-scale surface after drying were elucidated under solid-sliding conditions. These findings provide a basis for further research on bio-derived materials for interfacial lubrication.
A comprehensive multiscale surface characterization framework is developed to systematically investigate the surface microtopography, spatial correlations, multiscale complexities, and tribological behaviour of laser-directed energy deposited IN718 coating finished by grinding and chemical-assisted magnetorheological finishing (CAMRF) (with glyceregia reagent) process. The corresponding framework integrates advanced analytical tools including scale-sensitive fractal (SSFA) analysis, continuous wavelet transform (CWT), power spectral density (PSD), and spatial uniformity and directional error distribution analysis. SSFA and CWT facilitate the assessment of scale-dependent complexity and fractal characteristics, whereas PSD quantifies the contribution of different wavelength components to overall surface structure. The combined analyses indicates that the CAMRF-processed surface exhibits reduced multiscale complexity, improved spectral coherence, and enhanced spatial consistency. Furthermore, the multiscale topographical characteristics are found to be consistent with the observed tribological response, which demonstrates the capability of developed framework for correlating surface microtopography with functional performance.
