Search Results (679)

We aimed to address the issue of fretting wear on the rollers and raceways of pitch bearings in wind turbines during shutdown and under intermittent high loads. This study focuses on triple-row cylindrical roller bearings. A finite element wear simulation of the contact area between a single roller and the raceway was established based on Hertzian contact theory and the modified Archard model. The wear coefficient values of the model before and after coating were verified through experiments, with results of k₁ = 3.125 × 10⁻⁸ and k₂ = 4.5 × 10⁻¹⁰, respectively. The effects of normal load, displacement amplitude, and cycle number on the fretting wear behavior of rollers under both uncoated and GLC-coated conditions were investigated. The results show that the GLC (Glassy Carbon-like Carbon) film significantly reduces the friction coefficient and wear. Compared to uncoated rollers, it reduces the maximum wear depth by approximately 90.53% across various normal loads, displacement amplitudes, and numbers of cycles. Additionally, the wear rate of the coated rollers remains consistently low with small fluctuations. The conclusion holds that the GLC film reduces the interface shear force and effective slip amplitude, enhances surface hardness and stability, and improves the fretting wear resistance of pitch bearings by an order of magnitude under complex load and oil-starved conditions. The primary objective of this work is to investigate the mechanisms for enhancing the anti-fretting wear performance of pitch bearings, with the goal of significantly extending their service life and reliability in harsh operating environments. Full article

Background and objectives: Hemiarthroplasty (HA) remains one of the most common treatments for displaced femoral neck fractures in the elderly, providing pain relief, early mobilization and a low reoperation risk. Acetabular erosion is a recognized late complication of this procedure, but early cartilage wear and its potential relationship with infection remain poorly understood. The aim of this study was to describe the clinical and microbiological characteristics of patients who required conversion to total hip arthroplasty (THA) because of acetabular erosion and to analyze the possible role of unexpected infection as a contributing factor. Materials and methods: A retrospective observational study was performed including all patients treated between 2007 and 2019 who underwent conversion of a failed HA to THA due to acetabular erosion after femoral neck fracture. Microbiological analysis was performed in all cases through multiple intraoperative samples. Patients were classified into two groups, with and without infection, according to positive microbiological cultures. Results: Forty-four patients were included, with a median age of 80.5 years (74–85). The median time to acetabular erosion was 25.4 months (10.4–47.4). Infection was identified in six patients (13.6%), all within the first six months after fracture (p = 0.029). The median time to erosion was shorter in infected patients (4.0 versus 29.8 months, p < 0.001). No other demographic, functional, or implant-related variables were associated with infection. There were three re-revisions, two due to recurrent dislocation and one periprosthetic infection in a hip without unexcepted positive culture. All patients with positive intraoperative culture were successfully managed with antibiotherapy. Postoperative functional scores improved significantly in both groups. Fifteen patients (34.1%) died during follow-up. Conclusions: Early acetabular erosion after hemiarthroplasty may represent a manifestation of previously unrecognized low-grade infection, particularly in frail elderly patients. Despite advanced age and multiple comorbidities, conversion to THA achieved significant functional improvement with an acceptable complication rate. Prospective studies with larger populations are warranted to confirm the relationship between infection and early acetabular cartilage loss. Full article

This study examines the rheological and tribological behavior of bio-based nano-lubricants enhanced with cerium oxide (CeO₂) and multi-walled carbon nanotubes (MWCNTs), alongside the application of artificial intelligence (AI) models for performance prediction. Rheological results confirmed non-Newtonian, shear-thinning behavior across all formulations. CeO₂-based lubricants exhibited significantly higher viscosities at 40 °C (up to ~3700 mPa·s at low shear), which decreased sharply with shear, indicating strong particle interactions. In contrast, MWCNT-based lubricants maintained moderate viscosities (90–365 mPa·s at 40 °C) with improved flowability due to nanotube alignment. At 100 °C, both systems showed viscosity reduction, stabilizing between 8 and 18 mPa·s, which favors pumpability in high-temperature applications. Tribological testing revealed distinct performance characteristics. CeO₂ lubricants showed slightly higher coefficients of friction (0.144–0.169) but excellent wear resistance, achieving the lowest wear rate of 1.66 × 10⁻⁶ mm³/N-m. MWCNT-based lubricants offered stable and lower CoF values (0.116–0.148) while also providing very low wear rates, with MCO6 achieving 1.62 × 10⁻⁶ mm³/N-m. However, ternary blends (C20T80 and M20T80) displayed moderate CoF but significantly higher wear rates (up to 2.92 × 10⁻⁵ mm³/N-m), suggesting that blending improves dispersion but weakens tribo-film stability. To complement the experimental findings, support vector regression (SVR), artificial neural networks (ANN), and AdaBoost algorithms were employed to predict key performance parameters based on compositional and thermal input data. The models demonstrated high prediction accuracy, validating the feasibility of AI-driven formulation screening. These results highlight the complementary potential of CeO₂ and MWCNT additives for high-performance bio-lubricant development and emphasize the role of machine learning in accelerating material optimization for sustainable lubrication systems. Full article

Wave Energy Converters (WECs) depend on hydraulic Power Take-Off (PTO) systems in which elastomeric seals must withstand wear, fatigue, and corrosion under harsh marine loading. This study quantitatively compares two commercial polyurethane seals (E1-E2) with custom-compounded Ethylene propylene diene monomer rubber (EPDM) formulations (E3–E5) using reciprocating wear tests (ASTM G133) at 3–10 N and 10–30 mm/s. It is noted that all experiments were conducted under dry conditions at room temperature as a baseline assessment, and the findings provide foundational insight prior to considering lubrication, hydraulic fluid effects, and marine environmental conditions relevant to WEC operation. Coefficient of friction (COF), specific wear rate, and worn-surface morphology were assessed to determine material durability. The commercial thermoplastic polyurethane (TPU) grades exhibited high hardness (93–94 Shore A), low wear rates (2.29–1.93 × 10⁻⁴ mm³/Nm), and shallow wear scars (≤380 µm). Carbon-black-reinforced EPDM (E3) produced the lowest wear rate among all samples (1.45 × 10⁻⁴ mm³ N⁻¹ m⁻¹) and the longest predicted service life (6.2 years), whereas silica-filled and plasticized EPDMs (E4, E5) showed higher wear (2.44–2.88 × 10⁻⁴ mm³/Nm) and broader deformation zones. Archard-based lifetime estimates at 10 N and 30 mm/s ranged from 3.1 to 6.2 years across materials. These results demonstrate that optimized EPDM formulations can serve as cost-effective alternatives to commercial TPUs for medium-load hydraulic sealing applications while providing a quantitative basis for material selection and life prediction. Full article

Although micro-arc oxidation (MAO) coatings are widely used due to their corrosion and wear resistance, their inherent micro-pore defects seriously affect their service life. The conventional sealing materials to these defects often fail to bond well with the pore wall due to volume shrinkage during curing, resulting in a service life that still does not meet expectations. Here, a novel pore-sealant is prepared to overcome the issue by adding nano calcium sulfoaluminate (CAS) expansive fillers. The modified CAS particles were compounded with glycidyl methacrylate (CAS sealant) and were driven to seal the micro-pores of MAO coatings by negative pressure. Results indicate that the surface porosity of the MAO coating decreased almost to zero after sealing treatment with the CAS sealant. Its low-frequency impedance |Z|_0.01Hz remained at 10⁸ Ω·cm² after 672 h of immersion, which is three orders of magnitude higher than that achieved by traditional sealing methods. The mechanism is that the interface defects at fillers/pore walls are filled by the sealant volume expansion due to CAS water absorption, which significantly inhibits the rate of corrosion medium penetration into the coating. Full article

The influence of electron beam melting (EBM) scan speed on the corrosion, nano-biotribological, and cellular adhesion properties of Ti-6Al-4V-ELI (extra low interstitials) was systematically investigated. Specimens were fabricated using five different scanning speeds, and tribological performance was assessed via reciprocating dry wear tests, while corrosion behaviour was evaluated through monitoring the open circuit potential and anodic potentiodynamic polarization tests in Ringer’s solution. Human fibroblasts from the FN1 cell line were used to assess cell adhesion. Specimens produced using scanning speeds of 4530 mm·s⁻¹ and 4983 mm·s⁻¹ exhibited increased passive current densities, indicating reduced corrosion protection, although all surfaces maintained the passive film characteristic. Tribological behaviour was strongly dependent on scan speed, with wear rate and penetration depth increasing at higher speeds; notably, an intermediate scan speed produced a surface with minimal wear and penetration depth despite a wide wear track, suggesting enhanced resistance to tribological degradation. Fibroblast cultures demonstrated robust adhesion and spindle-shaped morphology across all samples, with the disk produced using a scanning speed of 4983 mm·s⁻¹ showing the highest surface coverage, highlighting the role of EBM process parameters in modulating surface properties relevant to cell–biomaterial interactions. These findings underscore the critical influence of scan speed on the multifunctional performance of Ti-6Al-4V-ELI for biomedical applications. Full article

Copper (Cu) is widely used in electrical, electronic, and tribological systems owing to its excellent electrical and thermal conductivity. However, its relatively low hardness and poor wear resistance limit its use in demanding engineering applications. In this study, Cu-based hybrid metal matrix composites (MMCs) reinforced with hexagonal boron nitride (h-BN) and boron carbide (B₄C) were fabricated via spark plasma sintering (SPS) to improve their mechanical and tribological performance. The h-BN content was fixed at 1 wt.% to ensure solid lubrication, while the B₄C content was varied (0.25, 0.5, 0.75, and 1 wt.%) to examine its influence on the microstructural, mechanical, electrical, and wear properties of the composites. Microstructural analyses confirmed a homogeneous distribution of h-BN and B₄C particles in the Cu matrix at low and moderate reinforcement levels, whereas excessive B₄C resulted in partial agglomeration and reduced densification. All composites achieved relative densities above 95%, demonstrating the high densification efficiency of the SPS process. Hardness increased markedly with B₄C addition due to dispersion strengthening and grain refinement, while electrical conductivity decreased slightly because of the insulating nature of the reinforcements. Tribological tests showed that the composite containing 0.75 wt.% B₄C exhibited the best performance, with the lowest wear rate and stable friction behavior. Overall, the results indicate that co-reinforcing Cu with h-BN and B₄C through SPS is a promising strategy for developing multifunctional materials suitable for electrical contact and sliding applications. Full article

In the manufacturing sector, energy loss often stems mainly from wear. By improving the surface characteristics of alloys, we can substantially cut down on this kind of loss, which in turn boosts the efficiency of energy use. In this study, Fe₄₀Mn₁₉Cr₂₀Ni₂₀Mo₁ high-entropy alloy (HEA) with a face-centered cubic (FCC) structure was subjected to aluminum–nitrogen co-infiltration treatment via pack aluminizing and plasma nitriding, forming an aluminum–nitrogen co-infiltrated layer with a thickness of approximately 17 μm. An analysis was carried out on the microstructure, growth dynamics, and tribological behavior of the Al-N co-infiltrated layer across a broad temperature spectrum. The results showed that the surface hardness of the samples treated by aluminizing and Al-N co-infiltration reached 592 HV and 993 HV, respectively, which were significantly higher than that of the hot-rolled alloy (178 HV). The Al-N co-infiltrated HEA exhibited a low and stable friction coefficient as well as wear rate over a wide temperature range (20–500 °C), which was attributed to the formation of the Al-N co-infiltrated layer composed of AlN, CrN, and FeN phases. This study demonstrates that Al-N co-infiltration treatment is an effective surface modification technique, which can significantly enhance the hardness and tribological properties of high-entropy alloys over a wide temperature range. Full article

Sediment-laden seawater (1.4 kg/m³) under controlled flow velocities (1.5 m/s and 3.0 m/s) was employed to evaluate degradation mechanisms in static anti-fouling coatings. Exposure to 1.5 m/s sediment-laden flow induced a 49% reduction in adhesion strength, a 4.9–5.2° decrease in water contact angle, and an elevation in surface roughness from 0.32 μm to 0.88 μm after 30 days. Concurrently, antibacterial rate and anti-algal rate declined by 11.9% and 14.6%, respectively. In comparison, pure seawater scouring at equivalent velocity reduced adhesion by 30% and contact angle by merely 1.1°. Low-flow (1.5 m/s) conditions accelerated abrasive wear, driving severe surface roughening, whereas higher flow velocity (3.0 m/s) disrupted sustained particle–coating contact through turbulence generation, attenuating roughness progression. Crucially, low-flow conditions intensified abrasive wear and promoted severe surface roughening, whereas higher flow velocities generated sufficient turbulence to disrupt sustained particle–coating contact, thereby slowing the progression of roughness. These findings reveal a previously unrecognized, flow-velocity-dependent erosion mechanism: lower velocities encourage particle deposition and progressive surface damage, while higher velocities unexpectedly produce a protective, turbulence-mediated buffering effect that mitigates surface roughening. These findings establish a theoretical foundation for developing advanced anti-fouling coatings with enhanced resistance to sediment erosion. Full article

Surplus out-of-spec Al powders, typically discarded, remain an underused resource. Their reuse via alternative consolidation routes is a sustainable path for AlSi10Mg alloy recycling, but studies on the feasibility of such routes remain scarce. This study proposes a novel route combining powder compaction (under 50 kN and 80 kN loads) and remelting/solidification via suction casting to assess the feasibility of producing dense parts with enhanced properties. Microstructure, mechanical properties (compression and Vickers microhardness), and tribological performance (ball-crater wear under dry and abrasive conditions) were evaluated. The proposed route produced dense AlSi10Mg parts with low porosity levels (≤0.2%) and refined dendritic microstructures (spacing between 2.4 and 4.6 µm). Increased cooling rates promoted microstructural refinement, while higher compaction loads improved densification. The refined microstructure samples achieved compressive strengths above 500 MPa. Remarkably, microstructural refinement led to significantly increased hardness, with values reaching ≥100 HV. The samples compacted at 50 kN and subjected to the highest cooling rate exhibited the lowest dry wear rate (2.3 × 10⁻⁴ mm³/N·m), comparable to additively manufactured AlSi10Mg (AM) samples, confirming the efficiency of this recycling route. The dry wear rates ranged from 2.3 to 3.9 × 10⁻⁴ mm³/N·m, reinforcing the inverse correlation between hardness and dry wear performance. Although abrasive wear resulted in a material loss approximately 3 times higher than dry wear, it preserved the same microstructural dependence: finer, harder, and denser samples exhibited better wear resistance. Full article

The magnetic fluid seal (MFS) is a novel sealing technique that offers numerous benefits such as non-wear, long life, zero leakage, etc. There are numerous potential applications for it in the fields of energy and chemical industry, aerospace, machinery and electricity, etc. However, compared with a mechanical seal, the pressure of MFS is relatively low, which greatly limits its application promotion. Therefore, in this paper, a magnetic fluid sealing device with a dual magnetic source (present MFS) is firstly designed to improve the sealing pressure. Secondly, the effects of different sealing gaps, pole tooth heights, pole tooth angles and pole tooth eccentricity distances on the sealing pressure are investigated through numerical simulations to obtain the better combination of structural parameters for sealing performance. Finally, a test rig was built to confirm the reliability of the new device, and the results show that the new device’s sealing pressure is significantly higher than the conventional MFS’ at the same rate of rotation, with a maximum increase of 1.69 times and 1.71 times in sealing gas and liquid, respectively. This paper provides a reference for the improvement of sealing pressure of MFS in engineering applications. Full article

The oil and gas sector encounterssignificant material problems during acid stimulation, particularly under high temperatures, high pressures, and corrosive conditions with CO₂ and H₂S. This study focused on corrosion and erosion failures of tungsten carbide jetting nozzles in coiled tubing bottom hole assemblies. While tungsten carbide is durable, its high price, restricted machinability, and scarcity necessitate the search for viable alternatives. This study sought to identify and validate a low-cost, readily available, and easily machinable alloy with equivalent performance. A rigorous material selection approach took into account thermochemical stability, mechanical strength, and corrosion resistance under simulated downhole circumstances. Candidate alloys, both coated and uncoated, were subjected to extensive laboratory testing, including acid compatibility, high-temperature corrosion, erosion resistance, and mechanical integrity assessments. The majority failed due to pitting or surface deterioration. However, one coated alloy system was very resistant to chemical and thermal damage. To support long-term performance, a machine learning model relying on Gradient Boosting was created to forecast corrosion behavior using operational factors; demonstrating effective prediction characteristics compared with four other models. This AI-powered tool allows for accurate prediction of corrosion risks and aids decision-making by determining whether the material will maintain integrity under harsh acidic conditions. Field tests proved the selected alloy’s durability and jetting efficiency during many acid stimulation cycles. The corrosion and wear performance of coated 4145 material demonstrates a validated, cost-effective alternative to tungsten carbide with only four times lower corrosion resistance than carbide, outperforming other alloy combinations with up to 35 times higher corrosion rates. These results reveal tremendous opportunities for improving material design in corrosive energy applications. Full article

The low hardness of copper alloys, which are the substrate material used for continuous casting molds, makes them prone to plastic deformation, wear, and high-temperature oxidation, leading to premature failure and the formation of surface defects on billets. In this work, the microstructure, phase composition, mechanical, and tribological properties of Cr₃C₂–NiCr coatings deposited by high-velocity oxy-fuel (HVOF) spraying onto copper substrates used in molds were investigated. This research was driven by the need to extend the service life of copper molds in continuous steel casting processes. It was established that spraying parameters have a decisive influence on porosity, coating thickness, microhardness, and friction behavior under conditions simulating billet contact with the working surface of the mold. Among the investigated regimes, the coating deposited at a powder feed rate of 11.39 m/s exhibited a dense lamellar structure and the highest level of microhardness. Tribological tests confirmed that this coating exhibited the lowest coefficient of friction, whereas the other coatings were characterized by higher porosity and poorer wear resistance. Thus, the results emphasize the necessity of optimizing spraying parameters to develop highly effective HVOF protective coatings for copper molds operating under extreme thermomechanical loads during steel casting. Full article

Because of their exceptional strength, corrosion resistance, and low weight, materials such as titanium, aluminum, and others are becoming increasingly popular. The application scope of additive manufacturing (AM) in the aerospace sector continues to expand. Because of its high performance and low coefficient of thermal expansion, AlSi10Mg processed by laser-based powder bed fusion (LPBF) is becoming increasingly popular in lightweight aerospace component design. Nonetheless, the AM technique has a number of benefits; poor surface quality is the only drawback, necessitating post-processing. This study aims to focus on the machinability of AlSi10Mg under three distinct environmental conditions (dry, minimum quantity lubrication (MQL), and SL-MQL). The experimental investigations were centered on chip morphology, flank wear (Vb), surface roughness (Ra), and cutting temperature (Tc). SL-MQL reduced the roughness by 53–57% over dry machining and 23–29% over MQL condition, and in a similar way lessened the flank wear by 36–40% over dry machining and 12–15% over MQL condition. In addition, to check the predictive accuracy and optimize machining parameters, four machine learning models were used: Gaussian Process Regression (GPR), Bagging, Multilayer Perceptron (MLP), and Random Forest (RF). In both the training and testing stages, MLP consistently demonstrated superior performance across all parameters in comparison to other algorithms, achieving high levels of accuracy and low error rates. Full article

Plasma Transferred Arc (PTA) cladding is a versatile hardfacing technique that produces dense, metallurgically bonded overlays with excellent wear and corrosion resistance. However, optimizing bead shape is challenging due to complex multi-parameter interactions, an issue not fully addressed in existing studies. The bead morphology, defined by height, width, and penetration depth, remains highly sensitive to process parameters, directly affecting dilution and overall coating quality. In this work, single-pass powder PTA cladding was systematically studied using an orthogonal experimental design to assess the effects of arc current, powder feed rate, welding speed, oscillation width, and oscillation speed. A morphology index was proposed to integrate geometric attributes into a single metric for quality evaluation. Regression analysis and finite element simulations based on a Goldak double-ellipsoid heat source revealed that arc current is the dominant factor, where low-to-moderate values (100–115 A) promote wide–shallow pools and higher morphology index values, while higher currents induce excessive penetration and reduced stability. Multi-parameter coupling further indicated that optimal bead morphology is achieved under low-to-moderate current, a high welding speed, relatively high powder feed rate, wide oscillation width, and moderate oscillation speed. A representative optimal condition (100 A, 105 mm·min⁻¹, 35 g·min⁻¹, 10 mm, 2600 mm·min⁻¹) ensured minimal dilution and stable deposition. This integrative framework of orthogonal design, morphology index evaluation, and thermo-fluid simulation provides practical guidelines for parameter optimization and represents a novel combined approach for PTA bead optimization. Full article