Haitao Duan

To address the problem of cavitation damage and wear loss of turbine blades, cylinder liners for marine engines, valves in hydraulic systems, and other overflow components in long-term service underwater. This paper using laser cladding technology to prepare Al _x CoCrFeNi _2.1 high-entropy alloy coatings with different Al contents on the surface of 0Cr13Ni4Mo stainless steel. Investigates the effect of Al content on the tribological and cavitation performance of the Al _x CoCrFeNi _2.1 high-entropy alloy coatings. The results indicate that within the studied range of Al element content ( x = 0.1–0.9), the coating exhibits optimal wear resistance and cavitation resistance when x = 0.9. Compared with the base material, this corresponds to an 18.18% lower friction coefficient, 63.76% better wear resistance, and 12.6% improved cavitation resistance. In addition, with the increase of Al element content, the FCC phase of the coating gradually transforms to the BCC phase, forming a more obvious and uniform dual-phase structure consisting of FCC and BCC. This dual-phase structure improves the hardness of the coating while maintaining its toughness. It also helps reduce the coefficient of friction as well as the amount of abrasion and wear, and significantly enhances the coating’s cavitation resistance. This work provides technical guidance for the application of Al _x CoCrFeNi _2.1 high-entropy alloy coatings in cavitation-resistant coatings for hydraulic turbines.

The effectiveness of microstructural recovery (RE) in single-crystal (SX) superalloys remains poorly understood when creep damage is compounded by thermal or thermomechanical excursions. Here, we systematically distinguish creep, thermal, and thermomechanical damage by combining creep interruption, thermal exposure (TE), over-temperature creep (OC), rejuvenation heat treatment (RHT), and subsequent re-creep. A nickel-based SX superalloy was creep interrupted at 1000 °C/280 MPa and subsequently subjected to TE at 1200 °C for 2 h or OC at 1200 °C/80 MPa for 30 min. RE after creep interruption produced a stable total creep life extension exceeding 35%. TE generated secondary γ' precipitates without markedly degrading creep resistance, and RE extended the total creep life by 45%. In contrast, OC promoted premature γ' cutting by dislocations and pronounced creep degradation, limiting the life extension after RE to 23%. Microstructural analysis reveals that γ' and dislocation degradation is largely reversible, whereas carbide- and pore-related damage limits creep life restoration. γ' dissolution during RHT further facilitates dislocation annihilation and rearrangement into lower-energy configurations. These findings clarify the damage-dependent recoverability and define the applicability limits of RHT for life extension of SX superalloys under complex thermal and thermomechanical histories.

Titanium alloys have strong adhesion and a high wear rate, which limits their application in motion friction pairs. In this work, a stable in-situ copper phosphate (CuP) layer with a three-dimensional structure formed by interlocking CuP nanosheets was constructed on the titanium alloy surface. Under Polyalphaolefin 8 (PAO8) lubrication, the CuP layer and PAO8 formed a solid-liquid coupled lubrication system. Within this system, compared with the bare titanium alloy lubricated with PAO8, the coefficient of friction (COF) decreased by 79.60 % from 0.451 to 0.092, and the wear rate (WR) decreased by 99.69 % from 1.54 × 10-4 mm3/(N⋅m) to 4.85 × 10-7 mm3/(N⋅m). SEM-EDS results indicated that the in-situ constructed CuP layer could directly participate in the tribofilm formation, which effectively separated the contact surfaces of the friction pair and protected the titanium alloy surface from severe wear. It was the key to the significant reduction in WR. At the micro level, the results of molecular calculations showed that the interface between polar CuP nanosheets and non-polar PAO8 molecules generated Coulomb repulsion under the load, forming a solid-liquid coupled lubrication system and reducing lateral shear forces. Meanwhile, XPS analysis confirmed that the introduction of the CuP layer effectively suppressed the strong frictional chemical reaction of titanium alloy during the sliding process, reducing the formation of TiO2. This work developed an in-situ lubrication interface construction method, providing an effective solution to the problems of strong adhesion and high wear rate of titanium alloys.

Achieving ultralow friction in polymer-ceramic contacts typically requires complex material modifications or interface engineering. This study demonstrates that exceptional tribological performance can be unlocked through rational lubricant-polymer pairing, without altering the polymer. Specifically, polyetheretherketone (PEEK) lubricated by ethylene glycol (EG) against Si₃N₄ achieves an ultralow, stable coefficient of friction (COF = 0.0087) and exceptional wear resistance (specific wear rate = 0.99 × 10^-6 mm³ N^-1 m^-1), outperforming polymers like PTFE and UHMWPE. A comparative investigation of five polymers reveals that PEEK's superiority originates from a unique interfacial synergy with EG, manifesting as concurrent surface strengthening (≈34% increase in nanohardness) and in-situ formation of a continuous, highly ordered graphitic carbon transfer film on the counterface (lowest I_D/I_G = 0.48). Density functional theory calculations attribute this synergy to a geometrically matched, dual‑site chemisorption between the diols of EG and the carbonyl/ether oxygens on the PEEK backbone (binding energy = -0.01157 Ha), in contrast to the weak physisorption or suboptimal polar interactions observed for other polymers. This work establishes a clear structure‑affinity‑interface‑performance relationship and proposes a paradigm‑shifting design strategy for polymer tribosystems based on molecularly synergistic lubricant selection, paving the way for green, sustainable lubrication in precision engineering and biomedical applications.

To address the problem of cavitation damage and wear loss of turbine blades, cylinder liners for marine engines , valves in hydraulic systems, and other overflow components in long-term service underwater. This paper using laser cladding technology to prepare AlxCoCrFeNi2.1 high-entropy alloy coatings with different Al contents on the surface of 0Cr13Ni4Mo stainless steel. Investigates the effect of Al content on the tribological and cavitation performance of the AlxCoCrFeNi2.1 high-entropy alloy coatings. The results indicate that within the studied range of Al element content (X=0.1-0.9), the coating exhibits optimal wear resistance and cavitation resistance when X=0.9. Compared with the base material, this corresponds to an 18.18% lower friction coefficient, 63.76% better wear resistance, and 12.6% improved cavitation resistance. In addition, with the increase of Al element content, the FCC phase of the coating gradually transforms to the BCC phase, forming a more obvious and uniform dual-phase structure consisting of FCC and BCC. This dual-phase structure improves the hardness of the coating while maintaining its toughness. It also helps reduce the coefficient of friction as well as the amount of abrasion and wear, and significantly enhances the coating’s cavitation resistance. This work provides technical guidance for the application of AlxCoCrFeNi2.1 high-entropy alloy coatings in cavitation-resistant coatings for hydraulic turbines.

 The present investigation evaluates the effect of graphite-based filler (GBF) size on the mechanical and tribological performance of polyimide (PI) solid lubricant composites. During dry sliding tribological experiments, micron-, nano-graphite (MG, NG), and ultrathin graphene (GN) additives were considered. The results revealed that atomic-thickness GN outperformed micron- and nano-sized GBF filler in terms of mechanical and tribological performance when added into PI matrix. It was inferred that the GN was able to generate sufficient lubricating phases at the frictional interface due to their small size and ultrathin morphology, which provided them with enhanced tribological properties in comparison with the micro and nano-sized GBF fillers. GN oxidized by reciprocating shear force and friction heat at friction interface and subsequently formed lubricating layer consisting of graphene oxide (GO), as characterized by FTIR and Raman, spectroscopy. Atomistic modeling techniques was also used to elucidate the surface/interface lubrication mechanism, where GO was tightly adsorbed at frictional interfaces by van der Waals. The results facilitate better understanding of size effect on wear mechanism for solid lubricants.

The tribological behavior of polyether ether ketone (PEEK) composites modified with whisker carbon nanotubes (Wh‐CNTs) was systematically investigated across a wide temperature range (25°C–210°C) using reciprocating ball‐on‐disc sliding tests under a maximum Hertzian contact pressure of 290.72 MPa. Both the coefficient of friction (COF) and wear rate of pure PEEK and its composites exhibited a progressive increase with rising temperature. Advanced characterization techniques, including x‐ray photoelectron spectroscopy (XPS), laser Raman microscopy, and thermal emission scanning electron microscopy (FE‐SEM), were employed to analyze interfacial morphology, chemical evolution, and wear debris formation, elucidating the underlying wear mechanisms. Key findings revealed that the incorporation of 4 wt.% Wh‐CNTs facilitated the formation of a continuous heat‐dissipative transfer film on the GCr15 counterpart surface. Furthermore, temperature‐dependent structural transitions were observed: the 3D network of Wh‐CNTs evolved from a spherical architecture (analogous to rolling bearings) to an ellipsoidal configuration, significantly enhancing high‐temperature lubrication efficiency compared to fragmented structures. These results provide critical insights for predicting wear life and optimizing maintenance cycles of PEEK‐based composites in extreme thermal environments.