Cavitation Erosion Research Articles

Cavitation erosion performance and phase transformation strengthening behavior of laser clad iron-based shape memory alloy coatings

In order to avoid cavitation damage on the surface of overcurrent components after long-term service, the surface is reinforced with a coating to improve its cavitation resistance, thus prolonging service life. The present study employed analytical techniques, such as X-ray diffractometry (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), to investigate the cavitation erosion performance of laser clad Fe-Mn-Si-Cr-Ni shape memory alloy (SMA) coatings with focus on the enhancing mechanism of their martensitic phase transformation. The results indicated that laser cladding could produce high-quality SMA coatings, free of defects such as pores and cracks, resulting in a significant improvement in the cavitation erosion performance. After 5 h of the cavitation, the coated samples remained in the cavitation erosion incubation stage, demonstrating an accumulated mass loss rate of approximately 0.12 mg/h, merely 13 % of that observed in the matrix samples. Extensive microstructural delamination occurred in the matrix samples after 5 h of the cavitation, whereas the coated samples exhibited only "shear bands" formed by plastic deformation on the surface. The martensitic phase transformation from γ-austenite to ε-martensite served to dissipate the stress induced by cavitation bubble collapse on one hand, and, on the other hand, the robust nature of martensite produced a hardening effect, significantly enhancing the cavitation resistance of the coating.

NEW METHODOLOGIES FOR ASSESSING CAVITATION LOAD AND RESISTANCE OF STRUCTURAL MATERIALS AND PROTECTIVE COATINGS IN NUCLEAR POWER INDUSTRY. PART I. MONOFRACTIONAL APPROACH

The paper presents a new method for assessing the cavitation load and durability of structural materials and protective coatings. To determine the cavitation load on a rotating disk or other test rig, a new method for extracting erosion loads based on tests of reference materials on a reference cavitation rig is proposed. Direct measurements of the cavitation load in a cavitation tunnel with a slot cavitator, performed using piezoelectric sensors, made it possible to obtain information on the spatial distribution of the impact load. As an analytical function for modeling cumulative erosion curves in the monofractional approach, the logarithmic formula of L. Sitnik is used, assuming that cavitation erosion is a stochastic process described using fatigue theory. Armco iron is chosen as a reference material, in view of the weak dependence of its erosion rate on cavitation qualitative features. Therefore the local load value could have been extracted from the eroded surface profile of the Armco iron sample. Using the example of TiN coating analysis on stainless steel and VT3-1 titanium alloy, the time dependencies and threshold characteristics of their resistance were determined depending on the parameter of the density of the supplied energy.

NEW METHODOLOGIES FOR ASSESSING CAVITATION LOAD AND RESISTANCE OF STRUCTURAL MATERIALS AND PROTECTIVE COATINGS IN NUCLEAR POWER INDUSTRY. PART II. POLYFRACTIONAL APPROACH

A fractional approach to cavitation erosion process as proposed previously by one of the authors is explained. The polyfractional erosion process is considered as a superposition of a series of monofractional ones and described by a differential kinetic equation with a set of parameters constituting “the erosion resistance matrix”. The funda-mental methodological considerations are supplemented by describing the most typical applications including pre-diction of erosion of structural materials under given cavitation load, derivation of cavitation erosion fatigue charac-teristics, retrieval of effective erosive load basing on performance of reference materials. Finally, extending the methodology onto thin and thick protective coatings is proposed.

Effect of surface microstructure spacing on the cavitation erosion process of stainless steel

Fabricating microstructures on the surface is an innovative method to mitigate cavitation erosion (CE), but there are few studies focus on the effects and mechanisms of microstructure spacing on CE performance. This study has prepared a regular dot array-shaped microstructure with different spacings on the surface of samples. The CE experiments were carried out on both the microstructured samples and smooth samples through a magnetostrictive-vibration cavitation facility. Mass loss measurement and microscopic morphology were utilized to reveal CE characteristics. Numerical simulation was used to study the parameters of the flow field. The results clearly show that the microstructure spacing of 0.25 mm, 0.50 mm, and 1.00 mm samples can improve CE resistance. On these microstructured surfaces, the volume fraction of vapor is reduced and the bubbles move away from it. However, when the microstructure spacing enlarges to 1.50 mm, the damage inside the microstructure groove increases, which will reduce the CE resistance of the materials. As the spacing increases, the volume fraction of vapor on the sample surfaces will increase, and the bubbles in the microstructure groove will congregate, resulting in increasing damage. The research provides the dimensional basis for designing cavitation-resistant surface microstructures.

Improving the cavitation corrosion resistance of 6061 aluminum alloy by anodizing

Anodic oxidation is a common surface strengthening method to improve the comprehensive properties of aluminium alloys (AAs), such as wear and corrosion resistance, but its application on cavitation erosion is rarely touched. In this paper, the effect of sealing treatment on the properties of anodized AA6061 was investigated by using scanning electron microscopy (SEM), friction and wear experiment, cavitation experiment, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The experiment results showed that the oxide film under hydrothermal sealing had a superior cavitation and corrosion resistance, due to the high hardness and less defects in the film. Compared to distilled water conditions, corrosion mitigated the cavitation erosion of anodized AA6061 in simulated seawater, and the weight loss under simulated seawater after sealing was reduced up to a maximum of 30%.

Quantitative evaluation on the cavitation damage energy of metals via multiscale approaches

In-situ experimental observation cannot be an effective method in the impact process of metal cavitation erosion, and the impact damage energy prediction theory has not been established based on a detailed mathematical and physical model. Research has shown that the metal material can be regarded as a sensor to reflect the impact parameters. Soft metal materials such as industrial pure copper with a single α-phase microstructure can be a suitable sensor to detect cavitation erosion effects, revealing the impact behaviors of the cavitation jet through the depth, width and spatial distribution of cavitation pits on the surface. In this scenario, volume loss of cavitation pits on a macro/mesoscale are obtained by three-dimensional surface measurement. A coupled fluid-solid simulation model calculating the impact damage energy on a macro/mesoscale is established based on the Smoothed Particle Hydrodynamics (SPH) and the Crystal Plasticity Finite Element Method (CPFEM). Python programming is used to set the trajectory of SPH particles to determine the macro cavitation flow field. IFEM methods were used to construct the prediction theory of cavitation impact energy in a relatively simple exponential equation, establishing the quantitative relationship between cavitation impact damage energy and measured volume of cavitation pits. Compared with conventional measurement and simulation, the present multiscale approaches are assumed as a further step advancement towards calculating the impact damage energy of cavitation water jet.

On the effect of salt bath nitrocarburizing on the cavitation erosion behavior of AISI 304L stainless steel

In this study, salt bath nitrocarburizing was applied on austenitic stainless steel AISI 304L to stabilize austenite at the surface exposed to cavitation attack. Samples were treated at 470 °C and 500 °C for 6 h, giving an average thickness of the nitrocarburized layer of 6 µm and 26 µm, respectively. The thickness of the nitrocarburized layer is found to influence the formation of deformation-induced martensite (DIM) in the material and, thereby, the cavitation erosion resistance. The mass loss vs. time plot shows that the nitrocarburized specimens performed significantly better than the base material under ultrasonic vibratory cavitation erosion test (ASTM G32). Cross-sectional micrographs show that the phenomenon responsible for the failure in the base material is the formation of DIM. The specimen, nitrocarburized at 470 °C, showed a reduction of about 90 % in mass loss when compared to the base material (AISI 304L SS), owing to a higher yield strength (/resilience) after the formation of more stable austenite.

Salvinia-inspired surfaces for enhancing the preservation of air plastrons under negative pressure

The preservation of air plastron on a submerged microtextured surface under negative pressure has always been a challenge. In this study, the Salvinia-inspired surfaces (SIs) are fabricated and studied to enhance the preservation of air plastrons. The blade coating method and the selective UV/O3 surface treatment facilitated by an adaptive mask are applied for facile fabrication of the SIs with hydrophilic top but hydrophobic side and bottom. The air plastrons of both the SIs and regular hydrophobic surfaces (HBs) with singular and patterned cavities are experimentally visualized and theoretically deduced. The two-stage morphological behaviors of plastron expansion, together with quantitative geometric parameters, are compared between SIs and HBs under various negative pressures. The hydrophilicity effect on SIs effectively preserves the air plastron by reducing the critical negative pressure required for detachment by 90% compared to HBs. The ability of plastron preservation is proved on SIs with patterned cavities by hindering the coalescence of air plastrons. Our study benefits the cost-effective fabrication of Salvinia-inspired surfaces and provides a theory model to predict air plastron morphology and reveal its mechanism of enhanced air plastron preservation capability under negative pressure, which expands their underwater applications, such as migrating cavitation erosion. In the future, the capacity to retain air under high pressure requires further investigation.

Effects of cavitation and erosion on submersible drainage pumps: A numerical study

Submersible drainage pumps are used around the world both residentially and industrially for draining water and sewage. However, these pumps are prone to wear and clogging when the flows inward contain particles and air bubbles, and the combined effects of cavitation and erosion directly affect the performance of such pumps and degrade their efficiency. Therefore, it is essential to design a submersible pump that mitigates the adverse effects of cavitation and erosion. Reported here is an energy-efficient submersible drainage pump for use in emergency response. The combined cavitation–erosion effects are established in order to reduce their adverse impact on the pump, and how erosion wear affects the cavitation characteristics of the water in the pump is investigated. An experiment was conducted to verify the numerical results pump, and then, the influences of particle concentration and size on two-stage existing and altered model submersible pumps were analyzed using computational fluid dynamics. The results show that the performance of the altered model pump increased by 4.34%, with the cavitation–erosion effects reduced significantly. In addition, higher particle concentration induced higher erosion rates at both the leading and trailing edges of the impeller blades. Furthermore, the altered model significantly reduced the cavitation–erosion impact on the pump impeller blades compared to the existing model.

Effect of laser ablation over cavitation, slurry erosion, and surface properties of 86WC-10Co-4Cr based ceramic coating developed using HP-HVOLF

The manuscript presents a detailed study on WC-10Co-4Cr powder coatings applied via HP-HVOLF and subjected to laser ablation. FESEM analysis showed strong metallurgical bonding between the coating and SS410 substrate (≈75 MPa), crucial for durability. Despite the presence of cavities and pits, the coating's overall thickness remains consistent post-ablation, affirming stability. EDS mapping confirmed uniform elemental distribution, with well-bonded transition zones. Vickers hardness increased in laser-ablated samples (HV0.3 ≈ 1523) compared to unablated samples (HV0.3 ≈ 1344). Slurry and cavitation erosion analyses demonstrated superior resistance in laser-ablated samples due to higher microhardness and elevated static contact angles. Contact angle measurements indicated hydrophobicity in both un-textured and textured samples, with textured surfaces showing increased hydrophobicity.

Analysis on cause of erosion of guide vane of high‐head Francis turbine in sandy river

AbstractThe Kizilsu River Basin in China is located in the desert Gobi area with high sediment content and high hardness. After 4798h operation, the maintenance of a high‐head Francis turbine in this basin found that the guide vane was seriously worn, and even most of the top and lower skirts of the front of the guide vane were worn off. In this study, the k‐ε turbulence model, ZGB cavitation model and sediment erosion prediction model were used to simulate the solid‐liquid two‐phase flow and cavitation of guide vane. The research results show that the guide vane of a high‐head Francis turbine in a sandy river has a high sediment velocity and serious surface erosion, with the maximum erosion rate of 1.0 × 10−6 kg/(m2·s), while the area near the skirt of the guide vane is a low‐pressure area lower than the saturated steam pressure, and cavitation is very easy to occur, with the maximum vapor volume fraction of 0.9. Serious cavitation erosion occurs near the skirt of the guide vane, and the combined effect of sand erosion and cavitation erosion on the surface of the skirt of the guide vane aggravates the damage of the skirt structure. The research results provide a technical basis for the antiabrasion design of the guide mechanism of the high‐head Francis turbine and the operation and maintenance of the hydropower station in the sandy river.

Characterization of RF-Sputtered ZnO Thin Film Coatings on Aluminum (Al6061): Microstructure, Wettability, Cavitation, and Corrosion Analysis

The study focuses on the characterization of Aluminum (Al-6061) coated with RF-sputtered Zinc Oxide (ZnO) thin film, aiming to understand the complex interactions between microstructure, wettability, cavitation resistance, and corrosion performance. The study involves the use of various analytical techniques such as Field Emission Scanning Electron Microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and water contact angle (WCA) measurements. The cavitation erosion testing has been conducted under various factors namely jet velocity (m/s), impingement angle (°), and stand-off distance (cm), respectively, and that too at various levels. Further, with the use of RSM, the study also contributes to the interplay in between factors and acquiring optimized results. Moreover, the findings of the study provide valuable insights into the effectiveness of the ZnO coating in enhancing corrosion resistance and reducing mass loss due to cavitation erosion. The study’s results offer significant implications for the engineering and design of protective coatings for Aluminum surfaces, with the potential to enhance durability and performance in various industrial applications.

Non-destructive Evaluation of Cavitation Erosion Behavior of Alumina-based Ceramic Samples

Numerous industrial parts, devices, and processes are designed to withstand the conditions that lead to cavitation erosion. Metallic, ceramic, and composite materials used for these conditions must achieve specific mechanical characteristics required to resist cavitation erosion. When molten metal or alloy flows and comes into contact with refractory material or coated furnace linings, cavitation erosion can occur. This phenomenon is particularly expected in metallurgy, especially in casting operations. Alumina-based refractories, specifically low cement castable (ALCC), are often used in furnace lining applications due to their superior properties, such as high refractoriness, thermal stability, and mechanical characteristics. Mullite is another refractory material frequently used in foundry lining applications. It can be utilized as a coating in casting processes, such as the Lost Foam process, which is a novel method for producing high-quality, cost-effective castings. These two refractory materials were chosen to study their behavior under cavitation conditions. An ultrasonic vibratory test with a stationary specimen (ASTM G-32) was used for experimental cavitation determination. The results of mass loss and surface morphological parameters of degradation revealed that ALCC samples eroded predominantly at the surface, while the mullite samples exhibited more significant degradation by depth.

Effect of Si and prolonged time on interfacial morphologies and cavitation erosion behavior of directionally solidified Fe-B alloy in flowing liquid zinc

The effect of Si and prolonged time on interfaces and cavitation erosion behavior of directionally solidified (DS) Fe-B alloy in flowing liquid zinc was investigated. The results show Si enriches in α-Fe intragranular and α/Fe2B boundaries to refine textured grains. DS Fe-B alloy with 2.5 wt%Si exhibits the best cavitation erosion resistance to flowing zinc, which is attributed to formation of alternating distributed Γ-Fe3Zn10 and FeSi and subsequently columnar ζ-FeZn13. Cavitation erosion resistance mechanism of DS Fe-B alloy with 2.5 wt%Si is manifested that Si-induced Γ-Fe3Zn10 and FeSi and the rooting-whisker ζ-FeZn13 layer can inhibit spallation and cracks of Fe2B and products.

CAVITATION EROSION BEHAVIOR OF WC–Co COATINGS ON TURBINE STEEL DEPOSITED BY COLD SPRAY

A renowned hard coating material (WC–Co) has the potential to overcome cavitation erosion (CE) in hydromachinery components. Hydro turbines that employ silt-filled water for electricity generation create a lot of metal waste due to erosion and cavitation caused by the particles. There is an urgent need for repair of hydropower components that have undergone damage due to cavitation. In this investigation, tungsten carbide composite coatings were produced on 13Cr4Ni (CA6NM) stainless steel substrates using the cold spray method. In order to create high-quality coatings, nitrogen was used as the propellant gas. The coating microstructures were characterized by EDS, SEM XRD, and microhardness tests. Cold-sprayed WC–Co-based coatings were exposed to enhance the cavitation erosion resistance of CA6NM steel. Cold spray coating prepared with WC-12/17Co powder has shown excellent wear-resistant properties due to higher hardness and lower porosity.

Effect of Marine Bacillus Subtilis on Cavitation Erosion Resistance of HVOF-Sprayed WC-10Co-4Cr Coating in Artificial Seawater

Effect of Marine Bacillus Subtilis on Cavitation Erosion Resistance of HVOF-Sprayed WC-10Co-4Cr Coating in Artificial Seawater

Synergy effects of cavitation and particle erosion based on the Erosion/Corrosion Research Center erosion model

This study presents a new synergy model that incorporates the accelerated motion of particles resulting from bubble collapse. The model uses the Erosion/Corrosion Research Center erosion model to predict the combined effect of cavitation and particle erosion on wall surfaces. The results show that, compared with the conventional erosion model, the synergy model reduces the error in the erosion mass loss by up to 24.60%. The significant improvement in prediction accuracy confirms the effectiveness of the synergy model. The severity of sample erosion is positively correlated with the cavitation-inducer angle. The synergy effect leads to an increase in the extent and severity of erosion. Smaller particles demonstrate a more pronounced synergy effect, resulting in significantly accelerated motion and a highly concentrated particle distribution. High erosion rates are associated with high-speed impacts and small-angle impact zones, primarily caused by high-speed cutting erosion. This study presents a novel prediction method for exploring the synergy effect of cavitation and particles on wall erosion and investigates the motion characteristics of particles under this effect.

Cavitation flow characteristics on the surface of hydrofoil with microjet structure

A hydrofoil physical model is established based on the surface microstructure to mitigate the detrimental effects of cavitation phenomena on hydrodynamic machinery, such as cavitation erosion or surface damage. Tangential microjet structures are arranged on the hydrofoil's surface, and the modified k-omega shear stress transport (SST k–ω) turbulence model is employed to simulate the hydrofoil numerically. This simulation aims to analyze the effects of different chordwise positions and widths of microjet structures on the cavitation flow and performance of hydrofoils. The mechanism of cavitation suppression is revealed by coupling the chordwise position and width of the microjet structures. The results indicated that the chordwise position of the microjet structures near the trailing edge of the hydrofoil has a minimal impact on the hydraulic properties. The optimal chordwise positions are 0.5c and 0.6c, with the deviation rate of the lift-drag ratio within 3%. The optimum jet width is 0.5 mm, and the cavitation suppression is approximately 15% of the prototype hydrofoil. The microjet structures with tangential jets suppress cavitation by creating obstruction and suppression of the re-entrant jet. The tangential jet ratio of 0.3 represents the most effective tangential jet hydrofoil scheme, and the addition of tangential jets produces a significant inhibitory effect on the shedding of large-scale cavitation.

Microstructure, wettability, cavitation and corrosion performance of aluminum (Al6061) coated with RF-sputtered AlN thin film

This study addresses the challenge of enhancing aluminum substrates with AlN coatings for improved durability. Novel RF-sputtered AlN coatings were developed, demonstrating deposition with equiaxed crystals and a predominant presence of aluminum and nitrogen. The coatings exhibited hydrophobic properties as shown by contact angle measurements. Cavitation erosion resistance was systematically analyzed, revealing optimal parameters for minimizing mass loss, including jet velocity, impingement angle, and stand-off distance, thereby showcasing the protective role of the RF-sputtered AlN coating. Response Surface Methodology (RSM) provided insights into the correlation between operational parameters and mass loss, leading to process optimization with specific mass loss values and high desirability percentages. XPS analysis of corroded AlN on Al-6061 revealed aluminum compounds, sodium, NaCl, and oxidation products, aligning with SEM/EDS results and confirming the coating's effectiveness in mitigating corrosion. Carbon and oxygen were the most abundant elements by weight and peak area. Overall, this study offers valuable insights into the multifaceted performance and protective capabilities of RF-sputtered AlN coatings.

Microstructural transformation and corrosion–cavitation behavior of ultrasonic nanocrystal surface modified nickel aluminum bronze (NAB)

In this study, nickel–aluminum bronze (NAB) is optimized by ultrasonic nanocrystal surface modification (UNSM), and its surface microstructural evolution, surface hardness, electrochemical corrosion behavior, and cavitation erosion behavior are investigated. The potentiodynamic polarization curves and electrochemical impedance spectra before and after UNSM treatment of NAB are measured using a typical three-electrode system. The cavitation erosion process is simulated through the vibration of ultrasonic waves underwater, and the cavitation erosion resistance performance of various specimens is evaluated. UNSM significantly refines the coarse and heterogeneous multi-phase structure of the cast NAB, providing a relatively uniform and dispersed structure. Simultaneously, severe plastic deformation rapidly increases micro-strains on the NAB surface, which effectively improves its surface hardness from 211 to 360 Hv. After UNSM treatment, the corrosion potential increases slightly; and the passivation potential and current decrease considerably, dropping from 207 to 103 mV and from 5.23 to 2.41 mA/cm2, respectively. This is primarily because of the slowdown of selective-phase corrosion and the uniform formation of an oxide film. Additionally, UNSM parameters affect corrosion potential by regulating surface roughness. A smoother surface corresponds to a higher corrosion potential at the same load. UNSM treatment significantly improves the cavitation corrosion resistance of NAB, primarily because an increase in hardness and uniform distribution of structure effectively slows the speed of crack formation and propagation, which is a result of the synergistic improvement of mechanical and corrosion resistance properties.