Cavitation Resistance Research Articles

Fe-Cr-C-V hardfacing coatings with molybdenum addition: Wear, corrosion, and cavitation performances

The purpose of this study was to determine how molybdenum content affected the hardfacing coatings made of Fe-Cr-C-V that resist wear, corrosion, and cavitation. The hardfacing process was applied on the S235JR steel by the metal arc welding method. Apart from the chromium-rich M23C6 and M7C3 (M: Cr, Fe) carbides, the presence of molybdenum led to the development of M2C (M: Mo, Fe, Cr) carbides. As molybdenum and carbon concentration decreased, the size and volume fraction of M23C6 and M7C3 carbides tended to reduce. While molybdenum did not significantly alter hardness or wear resistance, it was found to be advantageous in terms of cavitation and corrosion. The coating, including 3 wt% FeMo, demonstrated a 20-fold increase in cavitation resistance compared to the coating devoid of molybdenum. The hardfacing coatings' resistance to corrosion was increased by up to 4.5 times with the addition of molybdenum.

Cavitation pit evolution process of epoxy and polyurea coatings on mortar substrates

This study focuses on unraveling the failure mechanisms of three distinct polymer-coating structures applied to mortar substrates: an epoxy coating (MEP1), an epoxy coating with an intermediate epoxy mortar layer (MEP2), and a polyurea coating with an intermediate epoxy mortar layer (MPU). Ultrasonic cavitation experiments are conducted to investigate the initial stages of cavitation erosion. The damaged surfaces of these three coating structures are meticulously investigated and characterized. An in-depth analysis is performed on the distribution characteristics of cavitation pits and the evolutionary patterns of these pits. The results indicate that the introduction of epoxy mortar as an intermediate layer significantly enhances the material’s cavitation resistance by improving its energy absorption capacity. This enhancement delays the formation of cavitation pits on the coating surface. Additionally, the superior adhesive properties of the intermediate epoxy mortar with the mortar substrate prevent direct cavitation erosion from forming on the substrate, even when brittleness failure occurs and coating erosion is observed on the surface epoxy polymer. The polyurea coatings demonstrate exceptional elastic–plastic deformation capabilities. When combined with the intermediate epoxy mortar layer, MPU can withstand prolonged and repetitive cavitation impacts, resulting in minimal coating erosion.

Bioinspired Solar-Driven Osmosis for Stable High Flux Desalination.

The growing global water crisis necessitates sustainable desalination solutions. Conventional desalination technologies predominantly confront environmental issues such as high emissions from fossil-fuel-driven processes and challenges in managing brine disposal during the operational stages, emphasizing the need for renewable and environmentally friendly alternatives. This study introduces and assesses a bioinspired, solar-driven osmosis desalination device emulating the natural processes of mangroves with effective contaminant rejection and notable productivity. The bioinspired solar-driven osmosis (BISO) device, integrating osmosis membranes, microporous absorbent paper, and nanoporous ceramic membranes, was evaluated under different conditions. We conducted experiments in both controlled and outdoor settings, simulating seawater with a 3.5 wt % NaCl solution. With a water yield of 1.51 kg m-2 h-1 under standard solar conditions (one sun), the BISO system maintained excellent salt removal and accumulation resistance after up to 8 h of experiments and demonstrated great cavitation resistance even at 58.14 °C. The outdoor test recorded a peak rate of 1.22 kg m-2 h-1 and collected 16.5 mL in 8 h, showing its practical application potential. These results highlight the BISO device's capability to address water scarcity using a sustainable approach, combining bioinspired design with solar power, presenting a viable pathway in renewable-energy-driven desalination technology.

Methods for increasing the cavitation and solid particle erosion resistance of 20GL and 30L steels based on their surface modification

The article presents the results of studies of cavitation and solid particle erosion resistance of samples of 20GL and 30L steels with various surface modification options based on nitriding and boriding processes. Tests for cavitation resistance were carried out according to the ASTM G134-17, and for solid particle erosion resistance - according to the ASTM G76-13. It was revealed that to increase wear resistance, the depth of modification of the considered steels should be at least 80 microns. Based on the totality of cavitation and solid particle erosion studies carried out, the best option for surface modification for 20GL steel is boriding, and for 30L steel nitriding.

Water storage capacity is inversely associated with xylem embolism resistance in tropical karst tree species.

Tropical karst habitats are characterized by limited and patchy soil, large rocky outcrops and porous substrates, resulting in high habitat heterogeneity and soil moisture fluctuations. Xylem hydraulic efficiency and safety can determine the drought adaptation and spatial distribution of woody plants growing in karst environments. In this study, we measured sapwood-specific hydraulic conductivity (Ks), vulnerability to embolism, wood density, saturated water content, and vessel and pit anatomical characteristics in the branch stems of 12 evergreen tree species in a tropical karst seasonal rainforest in southwestern China. We aimed to characterize the effects of structural characteristics on hydraulic efficiency and safety. Our results showed that there was no significant correlation between Ks and hydraulic safety across the tropical karst woody species. Ks was correlated with hydraulic vessel diameter (r=0.80, P<0.05) and vessel density (r=-0.60, P<0.05), while the stem water potential at 50 and 88% loss of hydraulic conductivity (P50 and P88) were both significantly correlated with wood density (P<0.05) and saturated water content (P=0.052 and P<0.05, respectively). High stem water storage capacity was associated with low cavitation resistance possibly because of its buffering the moisture fluctuations in karst environments. However, both Ks and P50/P88 were decoupled from the anatomical traits of pit and pit membranes. This may explain the lack of tradeoff between hydraulic safety and efficiency in tropical karst evergreen tree species. Our results suggest that diverse hydraulic trait combination may facilitate species coexistence in karst environments with high spatial heterogeneity.

Enhancing Efficiency and Reliability of Tidal Stream Energy Conversion through Swept-Blade Design

The current limited efficiency and reliability of tidal current turbines (TCTs) have posed significant challenges in effectively harnessing tidal stream energy. To address this issue, this paper undertakes both numerical and experimental studies to explore the advantages of swept blades over conventional straight blades in terms of energy capture efficiency and cavitation resistance. It is found that both the sweep length and sweep angle of the blade can influence the power generation efficiency of the TCT. For the particular swept blade investigated in this study, the highest power coefficient is achieved when the sweep length is 0.544 m and the sweep angle is 28.88°. The research also demonstrated that the swept-blade TCT shows a higher power generation efficiency than the straight-blade TCT across a broad range of rotor speeds. To be precise, with the swept blades, the power coefficient of the TCT can be improved by 5–17%, depending on the tip speed ratio. Additionally, swept blades exhibit a superior cavitation resistance. This is evidenced by their higher cavitation numbers across all tip speed ratios in comparison to conventional straight blades.

Neighbourhood species richness and drought-tolerance traits modulate tree growth and δ13 C responses to drought.

Mixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are more resistant to drought than monospecific forests remains contested. In particular, the trait-based mechanisms driving the role of tree diversity under drought remain elusive. Using tree cores from a large-scale biodiversity experiment, we investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; δ13 C) to changes in climate-induced water availability (wet to dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. We hypothesized that neighbourhood species richness increases growth and decreases δ13 C and that these relationships are modulated by the abiotic (i.e. climatic conditions) and the biotic context. We characterised the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance versus resource acquisition and stomatal control. Tree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods. The effects of neighbourhood species richness and climate on growth and δ13 C were modulated by the traits of focal trees and the traits of their neighbours. At either end of each drought-tolerance gradient, species responded in opposing directions during dry and wet years. We show that species' drought-tolerance traits can explain the strength and nature of biodiversity-ecosystem functioning relationships in experimental tree communities experiencing drought. Mixing tree species can increase growth but may not universally relieve drought stress.

Cavitation resistance of laser-sintered MS1 steel

This study focuses on the determination of cavitation rate for samples produced by Direct Metal Laser Sintering (DMLS) of MS1 maraging steel powder without any post-processing thermal or mechanical treatment (as-built). The test samples, fabricated using an EOSINT M280 machine in a nitrogen atmosphere, were evaluated for their cavitation resistance using the ultrasonic vibration method as proposed by the ASTM G32 standard. Surface characterization to determine the duration of the experiment, as well as during and after the experiment to analyze changes in surface characteristics, was conducted using Scanning Electron Microscopy (SEM). Additionally, chemical analysis was performed using the Energy Dispersive X-ray Spectroscopy (EDS) method before and after the experiment to identify any changes and locations of significant surface damage. The mass loss of the samples over time was measured to calculate the cavitation rate. The goal of this research was to explore the potential applications of laser-sintered MS1 steel powder for manufacturing machine components and parts that are subject to cavitation erosion, due to the numerous benefits of additive manufacturing over traditional conventional technologies.

Cavitation erosion of samples based on cordierite-talc ceramics

In the paper, the cavitation resistance of cordierite samples with the addition of 10%, 15% and 20% talc, sintered at 1200?C, was investigated. The ultrasonic vibration method with a stationary sample according to the ASTM G32 standard was applied. The formation and development of damage to the surface of the samples was monitored using a scanning electron microscope and the level of damage to the surface of the samples was quantified using image analysis. The change in the mass of the samples as a function of the cavitation time was monitored to determine the cavitation rate. By measuring the mass loss and morphological analysis of the pits formed on the surface of the sintered samples of the cordierite-talc ceramics, the mechanism of degradation and resistance to the effect of cavitation was monitored. The obtained results were compared with the results of earlier tests of cavitation resistance of sintered cordierite samples. The addition of talc in the mixture with cordierite significantly improved cavitation resistance of the sintered material compared to sintered pure cordierite. The tests were done to see the potential application of this material in hydrodynamic conditions, especially because of the strong corrosion resistance of these refractory materials.

Cavitation resistance of explosively welded aluminium/steel joint

Explosion welding is an unconventional method of joining two dissimilar metal materials, mostly used to clad dissimilar materials or when some unusual geometries need to be joined. Some of the bimetal joints obtained this way have applications in special cutting tools, transition joints, propellers and turbine blades, and therefore it is important to know the wear resistance of welded joints. In this research, explosive Demex, based on ammonium nitrate and trinitrotoluene, was used to weld plates of aluminium alloy AW-2024 and steel 1.0216. The welding procedure was carried out in the configuration of parallel plates. The quality of the welded joint was inspected on samples cut out from the welded plate by the method of microscopic analysis on the cross-section and by an ultrasonic cavitation test. Materials erosion in the zone of the welded joint after each of 4 cavitation cycles was observed using an optical microscope and by monitoring the mass loss. The wear resistance of the created bimetal was analysed from the aspects of further exploitation.

The effect of three-type Vortex Generators (VGs) on NACA-0015 hydrofoil cavitation formation at different angles of attack

Cavitation, the formation of vapor bubbles on hydrofoil surfaces, poses a significant challenge to the performance and durability of marine vessels utilizing hydrofoils. Vortex generators, small structures embedded on the hydrofoil surface, have emerged as a potential solution for mitigating cavitation, but the optimal shape of vortex generators for achieving maximum cavitation resistance remains an open question. This study aims to address this challenge by systematically investigating the impact of rectangular, triangular, and circular vortex generators on the cavitation characteristics of a NACA-0015 hydrofoil. Utilizing computational fluid dynamics (CFD) simulations, the influence of these vortex generator shapes on cavitation inception and critical cavitation numbers will be evaluated under varying angles of attack and flow velocities. The findings of this study will provide valuable insights into the design and optimization of vortex generators for hydrofoil applications. Despite the effectiveness of vortex generators in mitigating cavitation, the optimal vortex generator shape for specific hydrofoil designs and operating conditions remains unclear. The precise mechanisms by which vortex generators suppress cavitation are not fully understood, requiring further investigation to optimize their design and placement. The durability and long-term performance of vortex generators under various environmental conditions, including turbulence and corrosion, warrant further evaluation. By addressing these unsolved challenges, this study will contribute to the advancement of vortex generator technology and its practical application in hydrofoil systems, leading to more efficient and reliable marine vessels.

The application of self-healing concept in Ni superalloys: Theoretical design and experimental validation

The self-healing mechanism has been newly applied in Ni superalloys to extend the creep lifetime during service. Quantitative selection criteria are proposed to screen the potential self-healing elements in Ni alloying system. Ti atoms and η-Ni3Ti precipitates are thus selected as the candidate healing atoms and the healing agent, respectively. The ideal composition interval for Ti to achieve the effective healing effects is computationally calculated as 0.076–0.1 mol fraction. On this basis, SHNi (self-healing Ni alloy) has been developed and compared with nSHNi (no self-healing Ni alloy). The creep lifetimes of SHNi alloys are observed 8–10 times higher than that of nSHNi alloys. Microstructure characterizations have shown that η-Ni3Ti healing agents in SHNi alloys can form site-specifically at the cavity sites during service. Meanwhile, the creep cavities in SHNi alloys present much smaller average sizes during creep, and the cavity growth rates are generally one magnitude lower compared to that of nSHNi alloys. The excellent creep properties of SHNi alloys can be well ascribed to their creep cavitation resistance brought by the self-healing behavior. The effectiveness of self-healing mechanism in improving the creep properties has proposed a new strategy in developing novel Ni superalloys.

Cavitation resistance of FeMnCrSi coatings processed by different thermal spray processes

Cavitation-resistant FeMnCrSi coatings were developed in the past years as a cost-effective alternative to Co-containing alloys to increase the lifespan of hydraulic machinery. The effect of different chemical compositions, surface finishing, and post-processing treatments was investigated for various processing techniques, namely: Arc Spraying Process (ASP), High-Velocity Oxy-Fuel (HVOF), High-Velocity Air-Fuel (HVAF), Plasma Transferred Arc (PTA), and Cold Gas Spray (CGS). This works consists of a compilation and review of original and literature results, and discusses the microstructure changes imparted by each type of processing and their impact on the coating properties and cavitation resistance. Low heat input high-velocity processes (HVOF, HVAF, CGS) developed a reduced degree of oxidation and porosity, accounting for a cavitation resistance higher than that of the coatings that ASP processed. In addition, ASP coatings showed reduced cohesive strength, with the oxidized inter-splat interface being a preferential site for crack propagation.

Prospects for the Use of Metal Surfaces Modified by Nanosecond Laser Radiation for Energy Applications

Laser technologies for processing metals used as heat exchange surfaces are unrivaled to solve a number of problems in the energy industry. This is explained by the fact that after laser radiation treatment, metal surfaces gain unique surface functional properties (extreme wettability properties, high resistance to corrosion in contact with traditional coolants, high abrasive and cavitation resistance). The study of the processes of evaporation, boiling, and condensation on such surfaces is hampered by one of the unsolved problems, which is the lack of the ability to predict the configuration of microtextures, for example, in the form of micropillars and microchannels with predetermined sizes. In this work, a graphic–analytical technique based on the use of ablation spot sizes for the formation of a given configuration and microtexture dimensions on traditional structural materials of heat exchange surfaces is developed. Based on experimental data, regime maps were constructed for the formation of microtextures on the surfaces of aluminum alloy AlMg6 and steel AISI 310. The prospects for using metal surfaces with a given microtexture formed by laser radiation to intensify the phase transition of coolants and control convective flows in a droplet lying on a heated surface were assessed. The obtained results can be used in the development of spray (drip) irrigation systems to provide thermal protection for heat-stressed equipment.

Magnetically controlled interface weaving of dual-layer heterogeneous coatings with active and passive anti-corrosion protection

Polydimethylsiloxane (PDMS) elastomer exhibiting remarkable corrosion resistance and fouling release properties. However, their performances are often compromised due to the weak interfacial adhesion with rigid substrates. Herein, we have developed an innovative dual-layer heterogeneous coating via magnetic-controlled interface weaving technology, achieving a seamless integration of PDMS with a rigid epoxy (EP) substrate. Magnetic nanoparticles (Fe3O4@MPDA-MBT) were strategically incorporated into the coating system, guided by a magnetic field to facilitate their interfacial migration. This controlled migration of nanoparticles resulted in the formation of interface layer between the EP primer and PDMS topcoat, leading to a sharp increase in PDMS adhesion strength (3.0 MPa), which is over 7 times greater than that of control counterpart (0.4 MPa). Additionally, Fe3O4@MPDA-MBT were selectively enriched adjacent to the metal substrate, thereby endowing the coating with outstanding corrosion resistance, due to the quick releasing of enough MBT inhibitors, as confirmed by electrochemical tests with high corrosion resistance value (2.2 × 108 Ω·cm2). Also, the topcoat PDMS enabled the dual-layer heterogeneous coating to achieve fouling-release and cavitation resistance.

Surface treatments for the improvement of mechanical and cavitation resistance of Al 6082 alloy

Surface treatments for the improvement of mechanical and cavitation resistance of Al 6082 alloy

An epoxy-modified polyurethane composite coating with repetitive self-healing function for anti-cavitation, anticorrosion, and antifouling applications

Erosion and fouling are important factors that affect the performance of power components of large cargo ships. Inspired by animal cartilage tissue, an epoxy modified polyurethane composite coating (FD-EPU) with reproducible self-healing properties was successfully prepared. FD-EPU was endowed with excellent resistance to cavitation, corrosion, and fouling due to the presence of functional reduced graphene oxide (FrGO) and 2-octyl-4,5-dichloroisothiazolinone (DCOIT). The introduction of FrGO with multiple hydrogen bonds into coatings increased the tensile strength of FD-EPU by 3.56 MPa and exhibited excellent cavitation resistance (with a mass loss of 4.7 mg under continuous cavitation for 60 h). In addition, the barrier effect of FrGO enabled FD-EPU to possess outstanding anticorrosion ability. After being immersed in 3.5 wt% NaCl for a duration of 15 days, the |Z|0.01Hz value of FD-EPU was found to remain at 9.18 × 109 Ω·cm2. The modification of epoxy resulted in FD-EPU coatings with improved adhesion by 53.5 % compared to non-modified coatings, with a bond strength of 23.8 MPa on stainless steel. The incorporation of DCOIT and FrGO endowed FD-EPU with good antifouling properties (removal of more than 97.5 % of bacteria and removal rate of microalgae up to 96.2 %). Furthermore, FD-EPU exhibited outstanding opto-thermal self-healing capability, with a self-healing efficiency of 61 % after 30 s of near-infrared light irradiation. This work provides a new inspiration for the protection of large cargo ship power components.

Effect of water temperature and induced acoustic pressure on cavitation erosion behaviour of aluminium alloys

Cavitation erosion is a major challenge for marine and fluid machinery systems. This study investigated the erosion performance of two as-cast aluminium alloys exposed to acoustic cavitation in water at temperatures of 10–50 °C and those were then compared with an extruded wrought alloy tested specifically at the temperature of maximum erosion. The results showed that the as-cast A380 alloy displayed exceptional resistance to cavitation erosion, with the lowest mass loss and surface roughness. This finding suggests that the as-cast A380 alloy is a suitable choice for lightweight, high-performance components in applications where cavitation resistance is critical.

Liquid hydrogen centrifugal pump optimization based on reducing hydraulic loss and improving cavitation

According to the operation parameters and the design experience parameters, a liquid hydrogen centrifugal pump was developed and tested to meet an application requirement of small flow and high head in cryogenic systems or cryogenic storage tanks. The test results showed that 6 m of hydraulic loss in the pump at the rated condition and the inlet pressure of the cryogenic fluid decreased and fluctuated, which resulted in the pump being prone to cavitation. To improve cavitation resistance and hydraulic efficiency of liquid hydrogen centrifugal pumps, the model was optimized based on the genetic algorithm of MATLAB applying 7 parameters of impeller taken as optimization variables, each sub-objective function was given corresponding weights, and the optimal solution combination at the minimum of the objective function was finally obtained, and an inducer was matched. The results showed that by reducing the angle of the inlet, increasing the diameter of the impeller, and adding an inducer, the cavitation performance of the pump can be improved and the hydraulic loss can be reduced by appropriately reducing the impeller outlet diameter, to improve the head of the pump.A comparison of the performance of the preposition inducer optimized pump with the preliminary pump shows that, at the rated condition point, the head was increased by 4.6 m resulting in an efficiency of 43%. A numerical calculation considered the thermodynamic effect of non-isothermal cryogenic cavitation on the Reynolds-averaged Navier-Stokes combined with the k-ε turbulence model was applied for getting the pump hydrodynamic performances. It was proved that the multi-objective optimization method and preposition inducers were effective, and the calculating results were by experimental data well. Feasibility of the model had been validated to a certain extent. It can bring a high level of pump optimization, integration, and quality to new and existing designs.

Non-Destructive Examination for Cavitation Resistance of Talc-Based Refractories with Different Zeolite Types Intended for Protective Coatings.

In many industrial processes that include fluid flow, cavitation erosion of different engineering structures (pumps, turbines, water levels, valves, etc.) during their operation is expected. Metallic, ceramic, and composite materials are usual candidates considered for application in such extreme conditions. In this study, the idea is to synthesize refractory ceramic material based on talc with the addition of zeolite for utilization as protective coatings in cavitating conditions. Two talc-based refractories with zeolites from two Serbian deposits were produced. The behaviors of the samples in simulated cavitation conditions were examined by an advanced non-destructive methodology consisting of monitoring mass loss and surface degradation using image analysis compiled with principal component analysis (PCA), interior degradation by ultrasonic measurements, and the microstructure by a scanning electron microscope (SEM). Lower mass loss, surface degradation level, and modeled strength decrease indicated better cavitation resistance of the sample with Igros zeolite, whereby measured strength values validated the model. For the chosen critical strength, the critical cavitation period as well as critical morphological descriptors, Area and Diameter (max and min), were determined. A Young's elasticity modulus decrease indicated that surface damage influence progressed towards interior of the material. It can be concluded that the proposed methodology approach is efficient and reliable in predicting the materials' service life in extreme conditions.