Tribology International最新文献

The height and spatial properties of a rough surface can be described by height distribution and height spectrum, respectively. However, when dealing with experimental surface data without additional processing, reasons such as surface defects and dimples could lead to undesired fluctuations in spectrum. In this study, we measured the height distribution and height difference autocorrelation function (HD-ACF) of rough surface obtained from both simulation and experiments. We confirmed that HD-ACF conveys the same information as height power spectrum. Moreover, starting from a rough surface with height obeying symmetric Gaussian distribution, by using warping transformation with design and adjusting the HD-ACF, we can obtain a numerical rough surface that conforms to the height distribution and HD-ACF of the target isotropic surface.

By adding a spoiler bulkhead within the trapezoidal tooth cavity, a labyrinth seal (LS) structure is constructed with a bulkhead-tooth cavity. This design allows the tooth cavities to be subdivided without changing the original seal dimensions, enabling fine-tuned control of the fluid flow field within the cavities to improve the sealing performance. Based on three-dimensional transient computational fluid dynamics (CFD) methods and the self-developed plate test platform of the clearance seal, the leakage control and rotordynamic stability of several typical bulkhead-tooth LSs such as cross tooth (CTLS), side tooth (STLS), bevel tooth (BTLS) bulkhead and standard tooth labyrinth seals (SLS) have been relatively analyzed. The results show that the maximum leakage rate reduction of the CTLS and STLS is approximately 25 % and 22 %, respectively, compared to the standard tooth LS, while the BTLS achieves a reduction of approximately 10 %. The effective damping of CTLS, BTLS, and STLS can be improved by 36.6 %, 21.3 %, and −19.7 %, respectively, while the effective rigidity coefficients increase by 56.1 %, 43.4 %, and 7.5 %, respectively. The more substantial vortex dissipation effect within the cross-tooth and bevel-tooth cavities of LS and its obstruction to the clearance jet can improve the leakage control ability of the BTLS and CTLS. Meanwhile, the stronger vortex and more uniform distribution of circumferential velocity and pressure caused by the increase in fluid viscosity have significantly improved both the direct damping coefficient and the cross-damping coefficient of BTLS and CTLS. The enhanced constriction effect of STLS at the cavity outlet can improve the leakage control ability of STLS, but when superimposed with the negative moments in the tooth cavities, results in significant negative direct stiffness and reduced direct damping coefficient.

Surface microtopography is the most concerned topic in chemical mechanical polishing, yet no method currently exists to predict its evolution process. This paper introduces an approach to predicting the surface microtopography evolution considering chemical-mechanical synergy and polishing pad-workpiece random contact. Experiments confirm the effectiveness of the model through height probability density, roughness Ra, and power spectral density curves. Both experimental and simulation results indicate that under stronger chemical and mechanical actions, the surface micromorphology smooths faster, but the stabilized surface roughness ends up being larger. The presented model serves as a significant tool for studying the wear mechanisms under chemical-mechanical synergy and provides guidance for optimizing chemical mechanical polishing processes.

Tribo-corrosion-fatigue coupling damage greatly affects the service safety of wire rope. A self-made test rig was employed to investigate the influences of fatigue load characteristics (amplitude, stress ratio, maximum) on bending tribo-corrosion-fatigue damage of wire ropes. The tribological properties and electrochemical corrosion of the wire ropes, and the coupling damage and mechanisms were discussed in detail. Results indicate a lower friction coefficient between wire ropes in artificial seawater. The main wear mechanisms in seawater are adhesive wear, fatigue wear, oxidation wear and corrosion wear as compared to abrasive wear, adhesive wear, oxidation wear and fatigue wear in pure water. Lower stress ratios amplify corrosion and adhesive wear. Fatigue fractures are mainly ductile, with stress ratio being a significant factor. Tribo-corrosion-fatigue coupling exacerbates damage in contact ropes compared to fatigue ropes. Seawater increases fatigue rope damage but reduces contact rope damage. Higher fatigue load amplitude and maximum value, and lower stress ratios, increase friction coefficient, deformation, volume loss, wire breakage, and decrease corrosion resistance. These findings provide essential data for assessing wire rope service life under seawater corrosion conditions and ensuring offshore drilling safety.

Herein, the anti-corrosive polymer brush functionalized MXene (P-MBTS₂MA@MXene) was successfully prepared via surface-initiated polymerization. First, the dopamine initiator (DA-Br) can self-assemble onto MXene nanosheets formation of initiator modified MXene (PDA-Br@MXene) via spontaneous oxidative polymerization, then the corrosion inhibitor MBT derivative MBTS₂MA monomer was grafted onto MXene nanosheets through surface-initiated atom transfer radical polymerization (SI-ATRP) to obtain polymer brush P-MBTS₂MA functionalized MXene (P-MBTS₂MA@MXene). The prepared P-MBTS₂MA@MXene served as lubricant additive, manifesting good tribological properties with a low COF of 0.098 % and 94.8 % wear-reduction, which is attributed to the shielding effect and protective film formed by P-MBTS₂MA@MXene. Additionally, the grafting P-MBTS₂MA endows MXene nanosheets with improved anti-corrosion property, which prevents further corrosion of the metal surface via releasing corrosion resistance molecule MBT.

Wear, corrosion and tribo-corrosion requirements for Zr alloys in extreme environments are increasingly demanding. The development of high-performance coating materials is an effective way to expand the application prospect of Zr alloys. Herein, we have successfully prepared Al_xNbTiV_0.1W_0.5Zr_0.3 HEA coatings on Zr alloy by laser cladding. The coatings are composed of two BCC and Zr-rich phases. The increase of Al content leads to the precipitation of B2 structure and TiAl phase. The coatings demonstrate superior long-term tribo-corrosion resistance in H₃BO₃-LiOH solution, owing to their high-strength phases and remarkable ability to resist pitting corrosion. This work provides a theoretical basis for design of HEA coating system with high performance on Zr alloy in a dynamic corrosive environment.

The purpose of this study was to investigate the relationship between the morphology of β phase and the wear characteristic of Ti-6Al-4V (TC4) alloy. The coefficient of friction of the equiaxed β phase structure was reduced by 34.0 % and the wear rate was decreased by 25.9 % compared to the layered β phase structure. The excellent strain coordination of the equiaxed β phase could maintain its wear resistance, which was because the shear stress was less concentrated. More $\frac{1}{2}<111>$ dislocations were activated in the equiaxed β phase, which made {110}<111> slip system easier to slip and it alleviates shear stress concentration. This study provided valuable evidence for improving their wear resistance.

Ni60A alloy powders doped with varying concentrations (0, 10 wt% and 20 wt%) of Ti₃AlC₂ MAX phase were coated on S31008 NiCr stainless steel substrate using atmosphere plasma spraying technique in this work. Comparative investigation was conducted to examine the effects of Ti₃AlC₂ additions on the microstructure evolution, microhardness, and wide temperature range (room temperature to 800 ^oC) tribological performance of the composite coatings. The findings demonstrated that the composite coatings were composed of γ-Ni, intermetallic hard metal borides, Ti₃AlC₂ and TiC phases, without any noticeable oxide phases. The 20 wt% Ti₃AlC₂ additions to the Ni60A alloy coating exhibited minimum imperfections in microstructure with a porosity drop of 65.8 %, and the highest microhardness which was enhanced by 64 % to 924 HV_0.515. After introducing of Ti₃AlC₂, the coefficient of friction decreased and appeared to distinguish itself by remaining minimal and stable at low-medium temperatures compared with an increase of more than 70 % at high temperatures. Ni60A-10 wt% Ti₃AlC₂ coating resulted in the lowest friction coefficient of approximately 0.45 from room temperature to 400 ^oC and it peaked to 0.78 at 800 ^oC, reducing by 19.6 % and 6 % compared to non-composite coating, respectively. The wear resistance of the composite coating was considerably improved with the increment of Ti₃AlC₂, and the coating with 20 wt% Ti₃AlC₂ showed the most significant reduction in wear rate: 18.5 % at room temperature, 45.2 % at 200 ^oC, 37.2 % at 400 ^oC, 60 % at 600 ^oC, 90.8 % at 800 ^oC. The lubricate layered Ti₃AlC₂ phases and the tribo-oxide film predominate composed of derivative NiO, Cr₂O₃ Al₂O₃ and TiO₂ played a critical role in antifriction and wear resistance. The wear mechanisms were accordingly conducted as abrasion and adhesion wear at low-medium temperature and transferred into tribo-oxidation wear at elevated temperature.

To repair oil drill pipe joints that have failed owing to dry wear and tribocorrosion, graphene-reinforced CoCrFeMo_0.5NiTi_0.5 high-entropy alloy composite coatings (HEACCs) were developed through high-speed laser cladding. The HEACC containing 1.5 wt% graphene exhibited dry wear and tribocorrosion rates that were 59.18 % and 32.20 % of those observed in the high-entropy alloy coating, respectively. The HEACC exhibited a corrosion current density of 2.475 × 10⁻⁷ A/cm². The HEACC containing 1.5 wt% graphene underwent progressive damage during dry wear owing to the combined effects of abrasive wear, which created furrows; adhesive wear, which led to flaking; and oxidative wear, which formed oxide layers. During tribocorrosion, chloride ions exacerbated surface damage caused by hard abrasives and asperities, intensifying corrosive–abrasive wear interactions.

The high temperature sliding wear behavior of microstructurally engineering in-situ sub-micron sized TiB₂ reinforced ZE41 composite was studied and compared with it’s base counterpart at varying loading conditions. The wear mechanism maps were constructed by correlating the microstructures of worn surfaces with different test parameters. The severe and catastrophic wear mechanisms like delamination and melt wear were wider in base and composite, while in the case of engineered composite, these zones are significantly narrow down. Due to the presence of thermally stable in-situ TiB₂ particles and bimodal precipitates in engineered composite, the material showed sufficient resistance against wear induced deformation. Furthermore, the study established scientific knowhow on high-temperature wear induced deformation behavior by analyzing microstructural evolution in wear subsurface zone.