Search Results (7)

Copper and its alloys are widely used in marine environments due to their excellent corrosion resistance and thermal conductivity. Cold spray technology can avoid the thermal damage to the underlying material and is suitable for the manufacturing and repair of parts. In this study, Cu coatings were prepared on 304 stainless steel substrates by high-pressure cold spray technology, and the effects of cold spray parameters on the microstructure, mechanical properties, and cavitation resistance were investigated. The coatings (Cu-N₂1, Cu-N₂2, and Cu-He) were prepared using distinct cold spray parameters: Cu-N₂1 and Cu-N₂2 employed nitrogen gas at 5 MPa/800 °C with different nozzle geometries, while Cu-He utilized helium gas at 3 MPa/600 °C. The results show that the porosity of the Cu coating prepared by cold spray technology is less than 0.1%. The coating treated with helium gas exhibits a higher bonding strength (81.3 MPa), whereas the coating treated with nitrogen demonstrates greater strain hardening (130–136 HV_0.1). XRD results show that no phase change or oxidation occurred for coatings under all cold spraying conditions. After the cavitation test, the mass loss of the Cu coating is significantly less than that of the as-cast copper. The Cu coating surface first develops holes, and with the increase in cavitation time, the hole area begins to increase. However, with prolonged cavitation exposure, the surface of as-cast copper has a large area of holes, and with the increase in cavitation time, the hole growth rate is faster. These observations indicate the cavitation resistance of the Cu coating prepared by cold spray is more than 10 times higher than that of the as-cast copper. This study highlights the potential application of cold spray technology in the preparation of high-performance anti-cavitation copper coatings. Full article

The cavitation phenomenon presents a significant challenge in pump operation since the losses incurred by cavitation adversely impact pump performance. The many constraints of conventional anti-cavitation techniques have compelled researchers to explore biological processes for innovative alternatives. Consequently, the use of bionanotechnology for anti-cavitation pumping has emerged as a prominent study domain. Despite the extensive publication of publications on biomimetic technology, research concerning the use of anti-cavitation in pumps remains scarce. This review comprehensively summarizes, for the first time, the advancements and applications of bionic structures, bionic surface texture design, and bionic materials in pump anti-cavitation, addressing critical aspects such as blade leading-edge bionic structures, bionic worm shells, microscopic bionic textures, and innovative bionic coatings. Bionic technology may significantly reduce cavitation erosion and improve pump performance by emulating natural biological structures. This research elucidates the creative contributions of biomimetic designs and their anti-cavitation effects, hence boosting the anti-cavitation performance of pumps. This work integrates practical requirements and anticipates future applications of bionic technology in pump anti-cavitation, offering a significant research direction and reference for scholars in this domain. Full article

The performance of an entire ship is increasingly impacted by propellers, which are the essential components of a ship’s propulsion system that have growing significance in a variety of aspects. Consequently, it has been a hot research topic and a challenge to develop high-performance antifouling and anti-cavitation coatings due to the issue of marine biofouling and cavitation faced by propellers in high-intensity service. While there is an overwhelming number of publications on antifouling and anti-cavitation coatings, a limited number of papers focus on integrated protective coatings on propellers. In this paper, we evaluated the development of antifouling and anti-cavitation coatings for ship propellers in the marine environment as well as their current status of research. These coatings include self-polishing antifouling coatings, fouling-releasing antifouling coatings, and biomimetic antifouling coatings for static seawater anti-biofouling, as well as anti-cavitation organic coatings and anti-cavitation inorganic coatings for dynamic seawater anti-cavitation. This review also focuses both on the domestic and international research progress status of integrated antifouling and anti-cavitation coatings for propellers. It also provides research directions for the future development of integrated antifouling and anti-cavitation coatings on propellers. Full article

Sol–gel coatings can provide anti-fouling and erosion resistance while being safe to use in the marine environment. MAPTMS/ZPO multilayer coatings deposited on the AA2024-T3 aluminium surface using the dip-coating method at three different thicknesses (2, 4, and 6 µm) are investigated in this work. The coatings are characterised in terms of physical and mechanical properties, and these properties are investigated in comparison to previously obtained cavitation erosion resistance levels of the coatings. Additionally, the efficiency of the coatings against biofouling was assessed using Phaeodactylum tricornutum, a marine diatom. The influence of the formation of organic–inorganic hybrid materials (OIHMs) from the prepared sols on the physical and mechanical properties of the coatings were analysed. A variety of techniques, including attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) measurements, pencil hardness testing, cross-cut adhesion testing, a roughness profilometer, and nano-indentation, were performed on the bare and coated substrates. The results indicated that the thickness, hydrophobicity, and adherence of the coatings are strongly affected by the roughness. The elastic strain failure (H/E) and resistance to plastic deformation (H³/E²) coefficients were higher than those of the bare substrate before and after the cavitation erosion test, indicating that the coating had a higher ability to withstand deformation in comparison to the substrate alone. Furthermore, the microscopic analysis of a marine diatom, Phaeodactylum tricornutum, revealed that coated surfaces exhibited a decreased rate of bacterial adhesion and biofilm formation. The data show that sol–gel formed coatings outperform uncoated AA2024-T3 in terms of hardness, elastic strain, plastic deformation, and biofouling resistance. These characteristics are attributed to the coatings’ mechanical and adhesive capabilities, as well as their tribological behaviour. Full article

Axial-flow pumps, in addition to providing high anti-cavitation properties, must have high anti-erosion properties to ensure the required lifetime of the pump. Erosion damage of surfaces occurs when the net positive suction head (NPSH) significantly exceeds its critical value. The object of the study in this article is the axial-flow pump with a specific speed of 600 in two alternatives: № 1 and № 2. By analysis of the flow in the impeller blade systems, the ratio value between the NPSH, which ensures the absence of erosion, and the NPSH3, at which pump operational failure occurs, was determined. Impeller variant № 1 did not provide the required ratio. Impeller variant № 2 had higher cavitation qualities, and the required ratio was achieved for it. Energy, cavitation, and erosion characteristics of the axial-flow pump with impeller № 2 in rotational frequency n = 2000 rpm were investigated. Easily breakable paint coatings were used for the accelerated study of cavitation erosion. The experiment was carried out at three different flow rates and confirmed the assumptions made—the pump with impeller № 2 was not affected by cavitation erosion at the optimum flow rate. Patterns of erosion zones were accompanied by calculations of vapor zones in the impeller. At flow rates less than the optimum, cavitation disruptions occurred and appeared behind the vapor region. As a result, the condition of ensuring erosion-free flow in the impeller of an axial pump with a specific speed of 600 was obtained, ensuring the ratio NPSH/NPSH3 > 2.5. Recommendations on designing of erosion-free flow part of the axial pump impeller were also obtained. Full article

Metallic coatings based on cobalt and nickel are promising for elongating the life span of machine components operated in harsh environments. However, reports regarding the ambient temperature tribological performance and cavitation erosion resistance of popular MCrAlY (where M = Co, Ni or Co/Ni) and NiCrMoNbTa coatings are scant. This study comparatively investigates the effects of microstructure and hardness of HVOF deposited CoNiCrAlY, NiCoCrAlY and NiCrMoNbTa coatings on tribological and cavitation erosion performance. The cavitation erosion test was conducted using the vibratory method following the ASTM G32 standard. The tribological examination was done using a ball-on-disc tribometer. Analysis of the chemical composition, microstructure, phase composition and hardness reveal the dry sliding wear and cavitation erosion mechanisms. Coatings present increasing resistance to both sliding wear and cavitation erosion in the following order: NiCoCrAlY < CoNiCrAlY < NiCrMoNbTa. The tribological behaviour of coatings relies on abrasive grooving and oxidation of the wear products. In the case of NiCrMoNbTa coatings, abrasion is followed by the severe adhesive smearing of oxidised wear products which end in the lowest coefficient of friction and wear rate. Cavitation erosion is initiated at microstructure discontinuities and ends with severe surface pitting. CoNiCrAlY and NiCoCrAlY coatings present semi brittle behavior, whereas NiCrMoNbTa presents ductile mode and lesser surface pitting, which improves its anti-cavitation performance. The differences in microstructure of investigated coatings affect the wear and cavitation erosion performance more than the hardness itself. Full article

This article selects studies on the preparation of fluorinated polyurethane-nano-alumina composite coating materials, and analyzes the anti-wear, water resistantance, and surface microstructure. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) shows that the polyurethane synthesized in this study does not contain hydrophilic –CH₂OH groups. The cavitation wear test depicts that the actual cavitation amount C of the Al₂O₃-FPU (4) (fluorinated polyurethane) coating is 0.9035 × 10⁻³ kg, and the anti-wear ability increases by 61.9% compared with FPU-0.5. The water-resistant test shows that the contact angle of water droplets on the surface of the coating increase from 95.3° of FPU-0.5 to 123.1° of Al₂O₃-FPU (4), and the water absorption decreases from 2.52% to 1.04%. Scanning electron microscopy (SEM) observation confirms that alumina particles can protrude on the coating surface and resist strong wear, while the C-F chain with high bond energy at the near-surface exhibits high strength and water resistance, which prevents wear from spreading deep into the coating. Differential scanning calorimetry (DSC) results show that the Tg_(HS) value of the hard segment phase decreases with higher external force. Notably, when the coating is subjected to erosion, which enhances the crystallinity of the hard segment phase, the tensile strength of the hard segment phase of the coating surface is improved, which supports the wear resistance. Herein, we show that the addition of nano-alumina to fluorinated polyurethanes can control high water and abrasion resistance. Full article