Reducing corrosion and wear has been a challenge to metal components in marine environments for a long time. However, the problems of high cost and low efficiency hinder the discovery of new anti-tribocorrosion multiprincipal element alloys (MPEA). This study reported a significant reduction in both wear and corrosion of single-phase CoCrNi MPEA through in situ laser-directed energy deposition (L-DED), which had only half the tribocorrosion rate of prealloyed samples. Furthermore, the structural evolution mechanism of in situ samples was revealed at different scales, and the interaction mechanism of tribocorrosion was clarified in detail. The results show that in situ samples had finer cells and higher microhardness due to solid solution strengthening and nanoprecipitation strengthening. The higher Cr₂O₃/Cr(OH)₃ ratio, higher R_ct, and lower I_pass indicated a denser and more protective passive film of the in situ samples. Furthermore, the in situ sample demonstrated superior tribocorrosion resistance, which was mainly due to a lower corrosion-intensified wear loss (W_C) value. Moreover, the load intensified the material loss of interactions between wear (W) and corrosion (S). This work will provide breakthroughs in the wear–corrosion trade-off of MPEA design and promote the application of anti-tribocorrosion MPEAs in marine equipment.

Tungsten disulfide (WS₂)-based coatings have excellent thermal stability and self-lubricating properties and are considered better lubricating materials at elevated temperatures. This work reports that a WS₂ coating can achieve ultralow friction behavior after sliding for a period of time when the ambient temperature increases to 400 °C; that is, the friction coefficient decreases sharply from 0.08 to approximately 0.025 (a decrease of 68.7%), which is a very interesting phenomenon. There is no doubt that the WS₂ coating will undergo more significant oxidation at a medium temperature. It is generally believed that oxidation is detrimental to the tribological properties of disulfide coatings because oxides formed at intermediate temperatures act as abrasive phases to increase friction and wear, which cannot explain the special ultralow friction behavior of WS₂ coatings at 400 °C. Therefore, the microscopic structural evolution of the transfer film during the friction process was investigated via Raman and high-resolution transmission electron microscopy. The formation of WO₃ nanocrystals (~15 nm) promotes the structural ordering of WS₂ around WO₃ nanocrystals. Then, incommensurate contact interfaces are spontaneously formed between WS₂ crystals with a (002) plane preference and adjacent WO₃ nanoparticles, thus achieving an ultralow friction state. This ultralow friction mechanism of the WS₂ coating provides guidance for the design of superlubricating coatings for elevated-temperature environments.

Molybdenum disulfide (MoS₂) is widely utilized as a lubricant in aerospace, machinery, and electronics applications because of its unique layered structure and interlayer slip characteristics. Understanding the tribological behavior of MoS₂-based films under various atmospheric conditions, including oxidizing and specialized atmospheres, is crucial for developing environmentally adaptive lubricants. Here, we fabricated pure MoS₂ and Ag-doped MoS₂/Ag composite films via magnetron sputtering, focusing on their tribological performance in argon, CO₂, and O₂ atmospheres. Our results demonstrate that the friction coefficients of both films in argon and CO₂ are comparable to those in vacuum, with these environments promoting the formation of a continuous tribofilm on the counterpart ball surface, thereby reducing the wear rates. Remarkably, in an oxygen environment, the MoS₂/Ag composite film results in a ~50% reduction in the friction coefficient (0.027) and a threefold decrease in the wear rate compared with vacuum conditions. This exceptional performance is attributed to the friction-induced metal oxide nanoparticles coated with Ag, which form a “brick‒mud” structure that slides with MoS₂ (002) nanosheets to achieve low friction and wear. Furthermore, the addition of Ag enhances the ability of the film to repair sliding interfaces, mitigating abrasive wear. Our study elucidates the mechanisms driving the low-friction behavior of MoS₂-based films in atmospheric environments, offering valuable insights for the development of high-performance lubricants for extreme conditions.

High-entropy alloys have made significant progress in high mechanical properties, wear resistance, and corrosion resistance properties. Excellent tribological properties, especially high-temperature lubrication, have become another sought performance. In this work, VAlTiCrW high-entropy alloy film with body-centered cubic (BCC) structure was prepared on superalloy substrate by magnetron sputtering. It is found that the VAlTiCrW film shows very low friction coefficient of 0.15 and a low wear rate of 10^-5 orders of magnitude at 800 °C. After 800 °C oxidation, the film can still obtain a friction coefficient of no more than 0.2 at 700 °C. XRD and TEM revealed the formation of ternary oxide AlV₃O₉ with preferred orientation of (002) crystal plane with large spacing of 0.71 nm on the wear surface of the film, a high-temperature lubricating phase that has not been reported, realizes the low friction coefficient. This AlV₃O₉ can be formed by tribochemical reaction under the thermal-mechanical action at 700 °C, but pre-oxidation at 800 °C is the prerequisite in order to form the precursors of V-rich and Al-rich oxide layer.

Because of profound applications of two-dimensional molybdenum disulfide (MoS₂) and its heterostructures in electronics, its thermal stability has been spurred substantial interest. We employ a precision muffle furnace at a series of increasing temperatures up to 340 °C to study the oxidation behavior of continuous MoS₂ films by either directly growing mono- and few-layer MoS₂ on SiO₂/Si substrate, or by mechanically transferring monolayer MoS₂ or hexagonal boron nitride (h-BN) onto monolayer MoS₂ substrate. Results show that monolayer MoS₂ can withstand high temperature at 340 °C with less oxidation while the few-layer MoS₂ films are completely oxidized just at 280 °C, resulting from the growth-induced tensile strain in few-layer MoS₂. When the tensile strain of films is released by transfer method, the stacked few-layer MoS₂ films exhibit superior thermal stability and typical layer-by-layer oxidation behavior at similarly high temperature. Counterintuitively, for the MoS₂/h-BN heterostructure, the h-BN film itself stacked on top is not damaged and forms many bubbles at 340 °C, whereas the underlying monolayer MoS₂ film is oxidized completely. By comprehensively using various experimental characterization and molecular dynamics calculations, such anomalous oxidation behavior of MoS₂/h-BN heterostructure is mainly due to the increased tensile strain in MoS₂ film at elevated temperature.