Cavitation Effects Research Articles

Vibration Diagnostics for Predicting Pump Failures

This study investigates the predictive potential of specific vibration patterns in assessing the structural integrity of centrifugal pumps, vital for industrial fluid transport. Despite their importance, these pumps often encounter performance issues attributed to vibration-related damage such as cavitation and corrosion. Addressing this gap, we employ advanced vibration analysis techniques to identify distinct signatures indicative of cavitation and corrosion progression. Our research aims to provide an early detection tool for maintenance by understanding these patterns. Through our method, we reveal significant correlations between vibration patterns and pump condition, offering implications for extending pump lifespan and enhancing maintenance strategies in industries reliant on such machinery. Highlights: Centrifugal Pump Operation: Impeller rotation transfers fluid. Vibration Analysis Significance: Essential for predictive maintenance. Cavitation and Corrosion Effects: Trigger vibration, erode surfaces. Keywords: Centrifugal Pump, Corrosion, Vibration

Development of prominent bonding strength in Al/Mg bimetal composites prepared by ultrasonic vibration-assisted compound casting: Effects of ultrasonic powers

In this work, the A356/AZ91D bimetal composites were prepared by ultrasonic vibration-assisted lost foam compound casting, and the effects of ultrasonic powers on interfacial microstructures and mechanical properties of the Al/Mg interfaces were investigated. Results revealed that the Al/Mg bimetal composites without ultrasonic vibration treatment (UVT) were heterogeneous, and the Al/Mg interface was composed of Al-Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) area and Al-Mg eutectic structures (δ-Mg+Al12Mg17) area. The Mg2Si particles were gathered at the IMCs area and an oxide film that mainly composed of Al2O3 was existed between the IMCs area and eutectic structures area. With UVT, the oxide film was eliminated and the gathered Mg2Si particles were refined and dispersed by the acoustic cavitation effect, and part of the Al3Mg2 and Al-Mg eutectic structures were transformed into the Al12Mg17 due to the promoted solute interdiffusion, which improved the homogeneity of the Al/Mg interfaces. Besides, the grains of the Al/Mg interface with UVT under ultrasonic power of 75 W were significantly refined. The thickness of Al/Mg interface was increased with the increase of the ultrasonic power. Due to the excessive heat induced by UVT under the further increased ultrasonic power, the cooling rates and the degree of supercooling were reduced, resulting in the coarsening of interfacial grains. The microhardness of the Al/Mg interfaces was increased and got more uniform by UVT. The shear strengths of the Al/Mg bimetal composites with UVT were enhanced to 61.4 MPa from 32.4 MPa, with an increase of 89.5 % compared with that of the Al/Mg bimetal without UVT. This could be ascribed to the removal of the oxide film, the refinement of the interfacial grains and the dispersed and refined Mg2Si particles achieved by UVT, which hindered the crack propagation during deformation.

NIR Light-Fuse Drug-Free Photothermal Armor-Piercing Microcapsule for Femoral Vein Thrombosis Therapy.

Acute thrombosis and its complications are leading global causes of disability and death. Existing thrombolytic drugs, such as alteplase and urokinase (UK), carry a significant bleeding risk during clinical treatments. Thus, the development of a novel thrombolysis strategy is of utmost urgency. Based on the previous work, the hollow structure of microcapsules (MC) is fabricated. Subsequently, armor-piercing MC, known as Fucoidan/S-Nitrosoglutathione/Melanin@MC (FGM@MC) is obtained, using a layer-by-layer (LBL) self-assembly method. Utilizing near-infrared (NIR) light as a trigger, the FGM@MC demonstrated photothermal thrombolysis at the site of thrombus due to its stable and outstanding photothermal properties. Simultaneously, photothermal stimulation leads to the release of a significant amount of nitric oxide from the FGM@MC, resulting in cavitation effects for mechanical thrombolysis. In vivo experiments confirmed the stable release of nitric oxide under NIR light irradiation. Treatment of femoral vein thrombosis in rats revealed that the thrombolytic effectiveness of FGM@MC+NIR (53.71%) is comparable to that of UK (59.70%). Notably, FGM@MC does not interfere with the coagulation function of rats and exhibits a favorable safety profile. In conclusion, this study demonstrates that the drug-free armor-piercing microcapsule has significant potential in the treatment of thrombosis, offering a safe and effective alternative to traditional thrombolytic therapies.

Influence of the Rotation Speed on the Internal Flow Characteristics of an Aircraft Fuel Gear Pump

A gear pump is a key rotary-displacement pump for aircraft fuel transportation in the aerospace industry. Due to the great ratio of power-to-weight condition demanded for gear pumps in aircraft fuel transportation systems, the parameter of the rotation speed is a matter of extreme concern affecting internal flow characteristics that determines the adverse effects of cavitation, fuel trapping, and vibration. However, the flow characteristics of an aircraft fuel gear pump influenced by the rotation speed have not been elaborated upon on yet. In this research, the flow characteristics of an aircraft fuel gear pump were studied by considering the influence of the rotation speed. An experiment for testing the external performance of an aircraft fuel gear pump was performed, and a corresponding numerical simulation of a gas–liquid two-phase flow was employed. Distributions of the velocity and pressure at the central cross-sections and their monitored transient developments were comparatively analyzed for different rotation speeds. It was found that a greater pressure oscillational amplitude accompanied by a higher frequency could be induced by a higher rotation speed, especially in the region of gear engagement. Additionally, cavitation evolution characteristics affected by the rotation speed in the fuel gear pump were discussed. The mechanism of cavitation generation in the region of gear engagement to withdrawal was revealed to be the quick release of a great amount of pressure. Furthermore, a dimensionless cavitation area was employed to quantify the periodic cavitation evolution, and the natural exponential development of the maximum dimensionless cavitation area with the rotation speed was determined through curve fitting. This study should be helpful for creating a deeper understanding of the internal flow characteristics of an aircraft fuel gear pump in scientific research and the external performance in aerospace industrial applications.

Insight into the Effects of Hydrodynamic Cavitation at Different Ionic Strengths on Physicochemical and Gel Properties of Myofibrillar Protein from Tilapia (Oreochromis niloticus).

Effects of different ionic strengths (0.2, 0.4, and 0.6 mol/L) and different hydrodynamic cavitation (HC) treatment times (0, 1, 2, 3, and 4 min) on the conformation and gel properties of tilapia myofibrillar proteins (TMP) were investigated. The results showed that the solubility of TMP was significantly enhanced (p < 0.05) with the increase in NaCl concentration, and the gel characteristics were significantly improved. After HC treatment of TMP, the average particle size was significantly reduced (p < 0.05) and solubility was significantly enhanced (p < 0.05) with the increase in treatment time, the internal hydrophobic groups and reactive sulfhydryl groups were exposed. The intrinsic fluorescence spectra showed the unfolding of the spatial tertiary structure of proteins, and the circular dichroism spectroscopy showed the significant reduction in the content of α-helix in the secondary structure of the proteins (p < 0.05). In addition, the WHC and gel strength of the TMP heat-induced gels were enhanced, which improved the microstructure of the gels, and scanning electron microscopy showed that the gel network of the TMP gels became denser and more homogeneous. Dynamic rheology results showed that HC treatment resulted in a significant increase in the final G' and G" values of TMP. In conclusion, HC treatment was able to improve the physicochemical structure and gel properties of TMP at different ionic strengths. This study presents a novel processing technique for the quality maintenance aspect of salt-reduced surimi gel products.

Investigation of hydrodynamic lubricant film breakdown between the journal and bearing in a high-speed coolant pump of electric vehicles

The high-speed coolant pump is essential for electric vehicle thermal management, ensuring optimal module temperatures. The pump impeller and bearing are combined into a rotor and then fit on a fixed shaft with a clearance, aiming to generate a complete lubricant film between the stationary journal and rotating bearing during pump operations. However, during the pump durability test under off-design conditions, severe wear occurred on both the journal and bearing. A novel simulation method based on computational fluid dynamics and dynamic mesh is developed to investigate the lubrication failure. User-defined functions are programmed to articulate the simultaneous rotation and whirl of the bearing, and the effects of temperature and cavitation are considered. Both the pump and bearing simulations closely align with experimental results. When the radial force of the pump rotor is steady, the bearing only rotates without whirling, and the bearing load capacity can counteract the maximum radial force of the rotor. However, the rotor experiences fluctuating radial forces over time, primarily attributed to elevated pressure levels at the volute tongue caused by the rotor–stator interaction. This phenomenon results in the bearing to rotate and whirl simultaneously. The load capacity generated by the backward whirl of the bearing is greater than that of the forward whirl. Nevertheless, the bearing whirl initiates a decline in the extremum values of lubricant film pressure. Subsequently, both load capacity and minimum film thickness exhibit a continuous decrease, eventually culminating in the breakdown of the complete lubricant film and resulting in contact wear failure. These new findings contribute to proposing measures to reduce wear under unsteady excitations.

Study on regeneration characteristics of granular activated carbon using ultrasonic and thermal methods.

Dye wastewater is a type of high-concentration, high chromaticity, and high salinity organic wastewater, which is generally treated with activated carbon adsorbent. The effective regeneration of granular activated carbon (GAC) is the key to reducing the operating cost of GAC in the wastewater treatment process. The regeneration characteristics of saturated GAC adsorbed on 288 orange dye wastewater were studied by using the ultrasonic coupled thermal regeneration method. The results showed that the regeneration efficiency of GAC adsorbed on 288 orange dye wastewater increased with the increase of ultrasound power. The optimal ultrasound frequency and regeneration temperature were determined to be 45kHz and 60 ℃, and the relationship between regeneration times and carbon loss rate was explored. The combination of ultrasound and high-temperature heating methods has successfully improved the regeneration efficiency of GAC and significantly reduced the high-temperature thermal regeneration time of GAC, thereby reducing the mass loss rate of GAC. The performance changes of fresh activated carbon (FAC), saturated activated carbon (SAC), ultrasonic regeneration of activated carbon (UAC), and thermal regeneration of activated carbon (TAC) during the combined regeneration process were explored by characterizing the regenerated GAC. Infrared characterization showed that the C-O group of GAC was significantly weakened after coupling treatment, indicating that ultrasonic treatment can significantly enhance the desorption effect of thermal regeneration. The microjet, shock wave, and cavitation effects generated by ultrasonic treatment restore the specific surface area of GAC, mainly increasing the micropore volume and pore size of GAC, and enhancing the treatment effect of thermal regeneration.

Studies on the Mechanical, Strengthening Mechanisms and Tribological Characteristics of AA7150-Al2O3 Nano-Metal Matrix Composites

Stir-casting with ultrasonic cavitation produced nano-Al2O3-filled AA7150 matrix composites in this study. The SEM microstructure study shows that all composites include nano-Al2O3 particles with consistent particle sizes and homogenous distribution. EDS and XRD showed no secondary phases or impurities in the composite. Optical microscopy showed intense ultrasonic cavitation effects, and nano-Al2O3 particles caused grain refinement in the AA7150 matrix. The composite’s mechanical characteristics improved when the Al2O3 nanoparticle weight percentage (wt.%) increased. With only 2.0 wt.% nano-Al2O3 particles, the composites yielded 232 MPa, 97.52% higher than the sonicated AA7150 matrix alloy. Multiple models were used to characterize the strength of the AA7150 nano-Al2O3 composite. The findings showed that thermal incongruity, Orowan strengthening, the Hall–Petch mechanism, and load transfer effects contributed the most towards the increased strength of the composite. Increasing the nano-Al2O3 wt.% in the AA7150 matrix improved hardness by 95.08%, yield strength by 90.34%, and sliding wear resistance by 46.52%. This enhancement may be attributed to the combined effects of better grain refinement, enhanced dispersion with dislocation strengthening, and better load transfer between the matrix and reinforcement, which are assisted by the inclusion of reinforcements. This result was confirmed by optical studies.

Experimental and numerical research on the coupled mechanisms of cavitation effect in a Venturi-type bubble generator

Venturi type bubble generator has a broad application in various fields and its bubble performance is closely related to the strong turbulent flow field. The interaction between bubble breakup and cavitation flow is not fully explained. In present work, the influence of cavitation on the suction performance and gas-phase transport pattern of a Venturi-type bubble generator is investigated by experiments and numerical simulations. The results show that the pressure ratio of 0.58 is the critical cavitation condition and the suction of the Venturi type bubble generator reaches the limiting value. The Venturi type bubble generator almost lost its suction capacity at the pressure ratio decreased to 0.27. However, the cavitation effect has a suppressive effect on the suction volume. The quasi-periodicity of the air inlet velocity pulsation and cavity development is highly consistent. Further research found that the blocking effect formed by return jets and pressure waves from cavity collapse is the main factor in reduced suction volume. The mechanisms of cavity shedding and collapse have a similar evolutionary model to the bubble breakup mechanisms in the Venturi-type generator.

Histotripsy: an innovative approach for minimally invasive tumour and disease treatment.

Histotripsy is a noninvasive medical technique that uses high-intensity focused ultrasound (HIFU) to treat liver tumours. The two main histotripsy methods are boiling histotripsy and cavitation cloud histotripsy. Boiling histotripsy uses prolonged ultrasound pulses to create small boiling bubbles in the tissue, which leads to the breakdown of the tissue into smaller subcellular fragments. Cavitation cloud histotripsy uses the ultrasonic cavitation effect to disintegrate target tissue into precisely defined liquefied lesions. Both methods show similar treatment effectiveness; however, boiling histotripsy ensures treatment stability by producing a stable boiling bubble with each pulse. The therapeutic effect is ascribed to mechanical damage at the subcellular level rather than thermal damage. This article discusses the mechanisms, treatment parameters, and potential of histotripsy as a minimally invasive procedure that provides precise and controlled subcellular damage.

Advances in using ultrasound to regulate the nervous system.

Ultrasound is a mechanical vibration with a frequency greater than 20kHz. Due to its high spatial resolution, good directionality, and convenient operation in neural regulation, it has recently received increasing attention from scientists. However, the mechanism by which ultrasound regulates the nervous system is still unclear. This article mainly explores the possible mechanisms of ultrasound's mechanical effects, cavitation effects, thermal effects, and the rise of sonogenetics. In addition, the essence of action potential and its relationship with ultrasound were also discussed. Traditional theory treats nerve impulses as pure electrical signals, similar to cable theory. However, this theory cannot explain the phenomenon of inductance and cell membrane bulging out during the propagation of action potential. Therefore, the flexoelectric effect of cell membrane and soliton model reveal that action potential may also be a mechanical wave. Finally, we also elaborated the therapeutic effect of ultrasound on nervous system disease such as epilepsy, Parkinson's disease, and Alzheimer's disease.

Effect of ultrasonic vibration on microstructural evolution, clad defects, and surface properties in laser direct energy deposition of Inconel 625

Laser direct energy deposition (DED) has some accompanying issues, such as existence of micropores, elemental segregation at grain boundaries, intergranular corrosion, etc. Therefore, the current work aims for a reduction in clad defects and enhancement in surface properties for laser direct deposition of Inconel 625 by implementing ultrasonic vibration. The acoustic streaming and cavitation effect induced by ultrasonic vibration results in the breaking of columnar grains, along with grain refinement and better elemental distribution in the matrix during the solidification process. The investigation is carried out for deposition using a 240 W Yb-fiber laser under the application of ultrasonic vibration with a variable amplitude of 6–13 μm (frequency: 33–28 kHz). A relatively higher vibration amplitude was found more efficient in converting long columnar grains into finer and uniformly distributed equiaxed grains, with a significant reduction in micropores. Further, it resulted in a shorter molten pool lifetime because of the generation of more nucleation centers, leading to better cooling. The above effects resulted in higher microhardness of the deposited layer. Further, the wear and corrosion resistance showed an improvement with the application of vibration, which may be due to the finer equiaxed grains, less porosity, and better elemental distribution at a higher vibration amplitude.

Effect of ultrasound treatment on the performance and segregation of Al–Cu alloy with different Cd contents

By applying ultrasonic treatment to ZL205A aluminum alloy melt containing different Cd contents and then using a tensile test, a scanning electron microscope experiment, and a metallographic experiment, the influence of ultrasonic treatment to ZL205A aluminum alloy melt on the properties of aluminum–copper alloy with different Cd contents in the liquid phase high-temperature region was studied. The effect of ultrasonic treatment on the solidification structure of ZL205A aluminum alloy was investigated. The results showed that there was no significant difference in the form of Cd and the solid solution rate of the aluminum alloy with different Cd contents in ultrasonic-assisted casting. However, the effect of ultrasonic waves on the high-temperature liquid phase of the melt of ZL205A aluminum alloy can effectively reduce the porosity defects in the solidification structure of the casting, refine the solidification structure, and make the structure more uniform. The ultrasonic cavitation effect can promote the formation and uniform distribution of Al–3Ti and improve the nucleation rate, and the effect can continue after heat treatment. This can solve the problem that increasing Cd content in ZL205A greatly reduces the toughness of castings while increasing the strength. The sample with a Cd content of 0.20% and with ultrasonic treatment has the highest strength, the average tensile strength is 475.5 MPa, and the yield strength is 381.75 MPa. However, compared with the conventional casting samples with the same Cd content, the decrease in elongation was significantly reduced.

Performance improvement of a double-suction centrifugal pump for water supply system based on energy loss analysis and cavitation behaviour prediction

ABSTRACT To gain a comprehensive understanding of the energy dissipation of a double-suction pump, analysing the energy loss of its various components is necessary. However, the liquid temperature in the double-suction pump remains almost constant, using the entropy production or dissipation method to evaluate energy loss is difficult. The traditional analysis method based on pressure drop cannot quantify the internal energy changes in each component. To solve this problem, a pressure energy loss evaluation approach is developed on the basis of the pressure drop theoretical analysis and numerical prediction, and the effects of cavitation on the energy loss are investigated. The structure of the volute casing is improved to enhance the performance based on energy loss analysis and cavitation behaviour prediction. The results show that the energy loss efficiencies for the suction casing, impeller, and volute casing are 0.55, 4.6, and 5%, respectively, at the design flow rate. The proportion of energy loss in the impeller and volute casing increased with a decrease in NPSHa. The RNG k–ε and k–ω turbulence models are chosen for the numerical simulation, and the numerically predicted results are verified experimentally.

Effects of Ultrasonic Treatment on Grain Refinement and Gas Removal in Magnesium Alloys

The effects of ultrasonic treatment on grain refinement and hydrogen removal in three kinds of magnesium alloys—Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys—were investigated in this study. After ultrasonic treatment, the grains of the magnesium alloys were refined to varying degrees. The degassing effect was characterized by measuring the densities and hydrogen content of ingots. The results indicated that the application of ultrasonic treatment in these magnesium alloys was able to remove hydrogen and obviously refine the microstructure. In this experiment, both the measurement of the density of the ingots and the solid-state hydrogen measurement reflected the degree of degassing. The highest degassing efficiencies were 53.8%, 67.5%, and 34.9% for the Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys, respectively. The lowest hydrogen content of the AZ80 alloy reached 8.2 cm3/100 g, and the corresponding tensile strengths were 174 Mpa, 79 Mpa, and 6.2%, which represented increases of 41.5%, 38.6%, and 87.9%, respectively. The cavitation effect and acoustic streaming effect with an appropriate ultrasonic treatment duration resulted in grain refinement, degassing, and the uniform dispersion of second phases. This can significantly improve mechanical properties and provide a basis for industrial production.

Magnesium and magnesium alloy dissolution by high intensity focused ultrasound: erosion/cavitation vs. Wave propagation

The dissolution of metals, influenced by mechanical and chemical factors, plays a crucial role in various applications. Ultrasonic irradiation has been explored for its ability to enhance dissolution rates and modify surface characteristics. In this study, we investigate the dissolution of magnesium (Mg) and magnesium alloys under high-intensity focused ultrasound (HIFU) conditions with frequency sweeping (wobbling). Our findings reveal distinct effects of cavitation and acoustic streaming on the dissolution process. For pure magnesium, ultrasonic treatment significantly increases dissolution rates compared to silent conditions. Negative frequency sweeps result in the highest dissolution rates, linked to increased cavitation activity, while positive sweeps reduce dissolution rates but maintain acoustic streaming effects. The removal of surface oxides is accelerated in all sonication conditions. Macro- and micro-roughness patterns on the surface correspond to the wobbling frequency range, with wavelengths matching the average ultrasonic frequency. However, dissolution is not uniform across the sample, and preferential attack occurs at the focal point during negative frequency sweeps. In contrast, magnesium alloys exhibit lower dissolution rates than pure Mg. The alloy's mechanical properties make it less susceptible to cavitation erosion but more sensitive to acoustic streaming-induced dissolution. Grain boundaries are preferentially attacked, revealing differences between ductile pure Mg and the harder, more cavitation-resistant, alloy. This study highlights the complex interplay between cavitation and acoustic streaming in the dissolution of magnesium and its alloys under HIFU conditions, shedding light on the limits and potential applications of this technique, particularly in microstructure analysis.

Monitoring acoustic cavitation effects in tissues under the action of HIFU based on ultrasound images

The cavitation effect plays a key role in the field of High-intensity focused ultrasound treatment. By monitoring cavitation to adjust the irradiation dose, effective control of cavitation effects can be achieved, which is crucial for ensuring the safety and efficacy of HIFU therapy. In this paper, a method for monitoring cavitation effects in tissues based on ultrasound images is proposed. First, support vector machine is used to rapidly and accurately determine whether cavitation has occurred. Then, the improved watershed algorithm is employed to extract the regions where cavitation occurs, and the extracted cavitation region images are reconstructed using the total focusing method based on sparse array elements. Finally, to validate the feasibility and stability of the proposed method and investigate the development patterns of cavitation effects. An experimental system was established to conduct cavitation effect monitoring experiments on fresh bovine liver and a simulated human tissue model. The experimental results showed that, except for the recall rate in the fresh bovine liver test set, all classification metrics are greater than 0.9, demonstrating the practicality of the model established in this paper. The improved watershed algorithm achieved average values of Dice Similarity Coefficient, accuracy and precision at 93.69%, 96.74% and 92.23% respectively, representing a significant improvement compared to the traditional watershed method. The proposed total focusing method based on sparse array elements can effectively improve imaging efficiency while ensuring reconstruction accuracy.

In Situ Analysis of the Effect of Ultrasonic Cavitation on Electrochemical Polishing of Additively Manufactured Metal Surfaces

Abstract The effects of a hybrid process that combines ultrasonic cavitation and electrochemical polishing on the electrochemical behavior and the resulting surface characteristics of additively manufactured 316-L stainless steel were investigated. In situ potentiodynamic scans and electrochemical impedance spectroscopy (EIS) were conducted to gain a fundamental understanding of the effect of ultrasonic cavitation on the electrochemical processes involved, considering the influence of electrolyte temperature at 60 and 70 °C. The potentiodynamic scans revealed that increasing the ultrasonic excitation amplitude from 20 to 80 µm at 20 µm intervals and temperature from 60 to 70 °C led to reduced polishing resistance, and elevated passivation current density at equivalent applied potentials, thus leading to an increased polishing rate. These findings are attributed to intensified cavitation near the material surface, which promoted anodic dissolution reactions and accelerated the polishing rate. In situ EIS measurements provided valuable information on the charge transfer resistance and double-layer capacitance and their influence on the hybrid process. Specifically, higher ultrasonic amplitudes and elevated temperatures contributed to enhanced electrical double-layer formation and ion adsorption, resulting in a faster rate of polishing, indicating the efficacy of the hybrid process. These findings enhance our understanding of the complex interactions between ultrasonic cavitation and electrochemical dissolution processes that occur during ultrasonic cavitation-assisted electrochemical polishing. The research provides valuable insights for optimizing the process and its potential application in the post-processing of metal additive manufactured parts.

Development of a high intensity focused ultrasound device for bio-samples preparation

A miniaturized, low-cost high-intensity focused ultrasound device is developed for the problems of cross-contamination and uneven sample fragmentation in conventional ultrasound devices. This device generates ultrasonic waves through a concave spherical self-focusing piezoelectric ceramic piece, and creates a cavitation effect in the focusing area to achieve sample fragmentation. The feasibility of the device is demonstrated by physical simulation, then a driving circuit with adjustable power is designed and manufactured to generate 0 ~ 22.4 W acoustic power, and finally paraffin-embedded sample dewaxing experiments are performed to verify the validation of the device. The experimental results show that the dewaxing efficiency and safety of the high-intensity focused ultrasound device is significantly better than those of traditional chemical methods, and this device is comparable with commercial ultrasonic instruments. In summary, the high-intensity focused ultrasound device is expected to be applied in automated nucleic acid extraction and purification equipment and has a broad application prospect in the field of sample pre-processing.

Effect of ultrasonic vibration-assisted laser cladding frequency on the microstructure and properties of Fe-0.5C-15Cr alloy cladding layers

In this paper, Fe-0.5C-15Cr wear and corrosion resistant alloy coating was prepared on 3Cr13 stainless steel surface by ultrasonic vibration assisted laser cladding technology. The effects of ultrasonic vibration frequency on the microstructure, microhardness and corrosion resistance of the coating were studied. The results show that the length of the dendrites of the cladding layer decreased significantly after ultrasonic vibration is applied, the grains size is refined significantly, and the morphology of the grain boundary carbides changed from fishbone-like to short rods, when the vibration frequency is 20.2 kHz, the grain refinement is the most significant, and the orientation of the dendrites is obviously weakened. The hardness of the applied ultrasonic vibration specimens increased by 10–20 HV0.2 relative to the non-ultrasonic specimens, with the increase of vibration frequency, the hardness of the cladding layer firstly increased and then slightly decreased, and the peak appeared at 20.2 kHz. The coefficient of friction of the specimens when the ultrasonic frequency of 20.2 kHz is applied is lower than that of the specimens with non-ultrasonic frequency by 12.8 %, and the abrasive wear rate is reduced by 14.3 %. After ultrasonic vibration, the pitting potential of the cladding layer increases, the dimensional passivation current density decreased, the width of the passivation zone becomes wider, and the intergranular corrosion reactivation rate decreased, When the ultrasonic frequency is 20.2 kHz and 20.4 kHz, the pitting corrosion resistance and intergranular corrosion resistance of the cladding layer are significantly improved. This is because the cavitation effect, resonance effect and acoustic flow effect of ultrasonic vibration promote the non-uniform nucleation, refine the dendrites and intergranular carbides, and promote the redistribution of the corrosion-resistant element Cr in the in-grain martensite and grain boundary carbides, increasing the content of Cr in the matrix, and thus improving the wear resistance and corrosion resistance of the cladding layer.