Cavitation Tests Research Articles

Influence of TiO2 Additives on Cavitation Erosion Resistance of Al-Mg Alloy Micro-Arc Oxidation Coating

Four ceramic coatings are fabricated on 6061 aluminum alloy substrates with a micro-arc oxidation technique in silicate electrolytes with different TiO2 nano-additive concentrations. To explore the cavitation erosion resistance of the micro-arc oxidation (MAO) coating, cavitation tests are performed using a vibratory test rig. After cavitation tests lasting 10 min, the mass losses, surface morphologies, and chemical compositions of the samples after cavitation tests are examined using a digital balance, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively. The results indicate that, in contrast to the aluminum alloy, the MAO coatings, by adjusting TiO2 nano-additive concentration, can decrease the mean depth of erosion rate (MDER) due to the cavitation damage, and lead to an excellent cavitation erosion resistance. The results also show that: In contrast to aluminum alloy, MAO coatings can decrease the MDER due to the cavitation damage in a short period of time by adjusting TiO2 nano-additive concentration. With the increase of TiO2 nano-additive concentration, the compactness and the surface hardness of MAO coatings decrease, which can easily lead to larger erosion pits.

Influence of adhesion strength on cavitation erosion resistance of diamond-like carbon coating

Purpose The disbonding of DLC coating is a main failure mode in the high-speed cavitation condition, which shortens the service life of the bearing. This study aims to investigate influence of adhesion strength on cavitation erosion resistance of DLC coating. Design/methodology/approach Three DLC coatings with different adhesion strengths were grown on the 304 steel surfaces by using a cathodic arc plasma deposition method. Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of a DLC coating. The cavitation mechanism of the substrate-coating systems was further discussed by means of surface analyses. Findings The results indicated that, the residual stress decreased and then increased with the increasing DLC coating thickness from 1 µm to 2.9 µm, and the lower residual stress can improve the adhesion strength of the DLC coating to the substrate. It was also concluded that, the plastic deformation as well as the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion strength. However, lower residual stress and better adhesion strength could help resist the occurrence of the coating fracture. Originality/value Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of the DLC coating. The plastic deformation and the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion of coating. Lower residual stress and better adhesion of coating could resist the occurrence of the DLC coating fracture.

Effect of chemical heat treatment on cavitation erosion resistance of stainless steel

The purpose of this paper is to study the effect of chemical heat treatments on cavitation erosion resistance of the 304 stainless steel. Three types of diffusion layers are prepared on the 304 stainless steel using gas nitriding, gas carburizing, and carbonitriding treatments. Phase composition and surface microstructure of the diffusion layers are characterized by X-ray diffraction and scanning electron microscopy. And then, the cavitation erosion behavior of the diffusion layers are tested and compared with the one of the 304 stainless steel. The cavitation test is performed in an ultrasonic vibration system integrated with an electrochemical workstation. The mass loss, scanning electron microscopic morphology, and electrochemical test are adopted to assess the surface damage of the diffusion layers. A measurement for the mechanical properties of the diffusion layers shows that the hardness and the elastic modulus of the gas nitrided diffusion layer, carbonitrided diffusion layer, carburized diffusion layer, and 304 stainless steel are 5.3 GPa and 260 GPa, 4.2 GPa and 236 GPa, 4.0 GPa and 210 GPa, 2.5 GPa and 193 GPa, respectively. A cavitation erosion test of 14 h shows that mass loss of the gas nitrided diffusion layer, carbonitrided diffusion layer, carburized diffusion layer, and 304 stainless steel is 5.19 mg, 8.97 mg, 14.37 mg, and 6.62 mg, respectively. The electrochemical test results also indicate that the gas nitrided diffusion layer has a higher corrosion resistance than the carburized diffusion layer, carbonitrided diffusion layer, and stainless steel under cavitation erosion condition. As a conclusion, the gas nitrided diffusion layer is capable of enhancing the cavitation erosion resistance of the stainless steel, while the carburized diffusion layer and carbonitrided diffusion layer increases the mass loss of the stainless steel under cavitation erosion condition.

고용량 경사류용 동력계를 이용한 프로펠러 단독시험 특성의 실험적 연구

In order to investigate Propeller Open Water (POW) characteristics for the high-speed propeller in Large Cavitation Tunnel (LCT), the high-capacity inclined-shaft dynamometer was designed and manufactured. Its measuring capacities of thrust and torque are ±2200N and ±120N-m, respectively. The driving motor is directly connected to the propeller shaft. Inclined angle of the propeller shaft can be adjusted up to ±10°. As the pressure inside LCT can be adjusted in the range of 0.1~3.0bar, we can carry out the POW test at high Reynolds number (above 1.0×106) without propeller cavitation and the cavitation test in uniform flow. After the new dynamometer setup in LCT, the Reynolds number variation test and propeller open-water test were conducted at the inclined angle of 0°and 6°. The present POW results of the new dynamometer are compared with those of the existing high-capacity dynamometer in LCT and of the dynamometer in the towing-tank. Through systematic model tests and comparison with their results, the performance of the new inclined-shaft dynamometer was verified. It is thought the POW test for the high-speed propeller should be better conducted at high Reynolds number.

An investigation on cavitation-corrosion behavior of Ni/β-SiC nanocomposite coatings under ultrasonic field

Ni/β-SiC nanocomposite coating was electroplated on the 17–4 PH SS (precipitation-hardening stainless steel) in modified Watt’s bath. The role of cyclic-cavitation (Duty cycle: 50%) on corrosion behavior of Ni/β-SiC nanocomposite coating in 3.5 wt% NaCl solution was investigated using open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The results of OCP tests demonstrated that cavitation led to positive shifts in the potential for Ni composite coating, while it caused the potential negative shifts in the case of 17–4 PH SS. The results of the polarization tests under cavitation condition exhibited positive shifts in potential and an increase in current density up to a specific anodic potential. In higher anodic potentials, the cavitation had a reverse effect on potential and current density. Moreover, it increased the overall corrosion current density. EIS measurements illustrated a severe reduction in electrochemical resistance of both 17–4 PH SS (from 228.15 kΩ.cm2 to 14.85 kΩ.cm2) and Ni composite coating (from 20.19 kΩ.cm2 to 5.00 kΩ.cm2) after 20 h of the cavitation tests. The cumulative mass loss measurements showed that the mass loss for the substrate (10.3 mg.cm−2) was about five times more than that of Ni composite coating (2.3 mg.cm−2). Also, in the coated specimen, the incubation time is increased and the growth slop of the accelerating period decreased under cavitation condition.

Cavitation erosion resistance of a non-standard cast cobalt alloy: Influence of solubilizing and cold working treatments

The wear behavior of a non-standard cast cobalt chromium alloy (Co30Cr19Fe), during vibratory cavitation test, was investigated. Low stacking fault energies (SFE) cobalt alloys deform by complex plastic deformation mechanisms, which enhance the cavitation erosion (CE) resistance, since the onset of localized stress, leading to fatigue failure and material removal, is delayed. The purpose of this work is to characterize the main operating deformation mechanisms during cavitation erosion testing of the non-standard Co30Cr19Fe alloy. As cast, solution treated, and 15% and 30% cold rolled specimens were tested. The as cast microstructure consisted of ~2 mm fcc alpha grains and hcp epsilon-martensite. The 1473 K solubilization treatment led to primary recrystallization and formation of 250 µm new grains. The 15% cold worked microstructure consisted of heavily deformed fcc phase containing deformation twins and epsilon-martensite. Ultrasonic cavitation testing was carried out, during 40 h, according to ASTM G32-09. The solubilized specimens presented the worst behavior, whereas, the 30% cold worked specimens were the most CE resistant. The CE results are discussed based on the microstructural parameters: amount of alpha fcc and epsilon-hcp phases, grain sizes, relative amounts of twinning, slip lines and strain induced martensite formation.

Research on failure of cementitious materials under rotary cavitation test

Utilizing the rotating cavitation erosion test device invented by Nanjing Hydraulic Research Institute (NHRI) to perform the persistent cavitation experiment on hardened cement paste and mortar, observing and analyzing the differences and similarities between cavitation and abrasion zone. Observing the cavitation erosion on the surface of cement-based materials and researching on the destruction of cement hydrations under cavitation process by adopting multiple modern material analysis apparatus, such as Scanning Electron Microscope (SEM), Energy dispersive X-Ray(EDX), X-Ray Diffraction(XRD) and thermal analysis(TG&DSC). Results implied that after continuous cavitation test for 2 hours, the microscopic structure of original defects becomes smooth, to be specific, the flake, rod shape-crystals are basically disappeared and the bottom of cavitation pits are shaped like some melted organizations. Hence the cavitation erosion on cement paste is not only a simple mechanical failure but also lead to the thermal decomposition on hydrations, which could cause the remarkable loss of hydration products on the surface of test blocks. The specific figures are as follows: the mass loss of cementitious substances is no less than 40% so as the loss of slaked lime is more than 25% during a 2 hours cavitation experiment. In that way, the considerable hydration mass loss is capable to cause a huge affection on deterioration of concrete structures.

Wear and Cavitation Erosion Resistance of an AlMgSc Alloy Produced by DMLS

Pin-on-disk and cavitation tests were performed on an innovative Al-Mg alloy modified with Sc and Zr for additive manufacturing, which was tested in annealed condition. The damaging mechanisms were studied by observations of the morphology of the sample surface after progressive testing. These analyses allowed the identification of an adhesive wear mechanism in the first stages of pin-on-disk test, which evolved into a tribo-oxidative one due to the formation and fragmentation of an oxide layer with increasing testing distance. Regarding cavitation erosion, the AlMgSc alloy was characterized by an incubation period of approximately 1 h before mass loss was measured. Once material removal started, mass loss had a linear behavior as a function of exposure time. No preferential sites for erosion were identified, even though after some minutes of cavitation testing, the boundaries of melting pools can be seen. The comparison with literature data for AlSi10Mg alloy produced by additive manufacturing technology shows that AlMgSc alloy exhibits remarkable wear resistance, while the total mass loss after 8 h of cavitation testing is significantly higher than the value recorded for AlSi10Mg alloy in as-built condition.

On the cavitation resistance of deep rolled surfaces of austenitic stainless steels

In the present work, two austenitic stainless steels (AISI 304 and AISI 316) were evaluated in cavitation tests with deep rolling treatments (DRT) on their surfaces. The results show that both steels exhibited better behaviour after the deformation process than in untreated conditions; however, the wear rate did not stabilize for the deformed surfaces due to the gradient of properties, attributed mainly to hardness profile of the material after DRT. A correlation between the cavitation erosion resistance and the fatigue strength is presented, with the cavitation wear rate and incubation time showing a good correlation with the fatigue strength coefficient in the case of high-cycle fatigue. In the case of low-cycle fatigue, a good correlation was established for the cavitation wear rate considering the Manson-Coffin theory of strain fatigue, assuming that the cavitation wear rate is inversely proportional to the fatigue life and using a fracture strain equal to the fatigue-ductility coefficient. In this case, a proportional constant around of 103 was found to establish the correlation for both steels. On the other hand, a linear correlation between the cumulative mass loss and surface roughness was separately established for steels under DRT conditions and untreated conditions. In addition, it was demonstrated that DRT is a great possible method for reducing the cost by wear.

Cavitation erosion testing of different cavitation-resistent materials and coatings using the cavitating jet method

An experimental test circuit was built with submerged nozzle with diameter 1.2 mm and inlet pressure 200 bar. Several specimens of different cavitation resistant materials used for hydraulic turbines (e.g. 13Cr4Ni) and coatings (e.g. tungsten and chromium carbides) were tested. Cavitating jet tests proved to be very efficient, sufficient cavitation erosion was obtained within 90 minutes. Comparisons between different materials were based on microscopic mapping of the eroded surfaces and SEM visualizations. Finally comparison between cavitating jet test and hydrodynamic cavitation tests using the orifice is presented. Duplex steel weld deposit proved to be the most cavitation resistant material

Outstanding cavitation erosion resistance of hydrophobic polydimethylsiloxane‐based polyurethane coatings

ABSTRACTCavitation erosion will create shock waves and water jets in turbulent flows. These impact pressures will affect the surface, which will lead to crack propagation and severe material degradation. In this study, we have developed hydrophobic polydimethylsiloxane‐based polyurethanes (Si‐PUx) with hydroxypropyl polydimethylsiloxane (H‐PDMS) and polytetramethylene glycol (PTMG) as mixed soft segments and 2,4‐tolylene diisocyanate, 1,4‐butanediol, triethanolamine as hard segments via a polycondensation reaction and studied its properties. The cavitation wear experiment showed that the cavitation erosion resistance of Si‐PUx coating continuously improved with the increase of H‐PDMS content, while the adhesion force of Si‐PUs reduced with the increasing of H‐PDMS content. The surface of Si‐PUx coating after cavitation test was observed using an optical microscope and three‐dimensional profiler. The cumulative mass loss of Si‐PUx with 12.5 wt % H‐PDMS was only 2.96 mg and the surface showed no obvious holes and cracks after 80 h cavitation. The results showed that cavitation resistance had a correlation with degree of water resistance, hardness, adhesion strength, and dynamic mechanical properties of coating. It seemed that the Si‐PUx coating could withstand a longer period cavitation erosion resistance compared to high strength epoxy, which could be used as protective coating for flow components under water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47668.

Cavitation erosion behavior of super-hydrophobic coatings on Al5083 marine aluminum alloy

Al5083 alloy is widely used in marine and ship building industries for the construction of ship structures due to its high strength, fatigue resistance, and relatively good corrosion resistance against salty water. However, cavitation is one of its limiting factors in some important parts such as propellers used for marine applications. In the current research, the cavitation erosion behavior of super-hydrophobic coatings deposited on Al5083 aluminum was studied. The super-hydrophobic coating process included anodizing the surface in sulfuric acid followed by the surface chemical modification process with two Triethoxy Octylsilane (KH-832) and 1 H,1 H,2 H,2H-Perfluoro Octyl-Trichloro Silane (PFOTS) classes. The cavitation test was conducted according to ASTM-G32 standard using the vibration amplitude of 20μ in distilled water. The surface damage on the super-hydrophobic coatings was investigated by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Cavitation erosion caused the surface roughness of the as-anodized sample to increase from 85.9 nm to 153 nm, whereas for the coated samples, the cavitation process resulted in surface smoothing. In fact, cavitation erosion decreased the surface roughness of KH-832 and PFOTS coated samples from 269 nm to 119 nm and from 251 nm to 167 nm respectively. The number of the cavities formed on the surfaces of KH-832 and PFOTS coatings was more than that in the as-anodized sample due to their rougher surfaces. However, the super-hydrophobic nature of the coatings resulted in the formation of small bubbles. Hence, the depth of the generated cavities in KH-832 and PFOTS samples was lower than that in the as-anodized sample. In fact, the cavities on the coated surface did not penetrate into the substrate and this enhanced the cavitation resistance of the sample. Finally, a model for the cavitation erosion behavior of PFOTS and the anodized samples was presented.

Analysis of the External Conditions Affecting on the Cavitation Resistance of a Steel

The aim of this study is to analyze the effect of cavitation erosion test conditions on the surface resistance of medium carbon steel. The ultrasonic vibratory specimen system was used to perform the experiments under the laboratory conditions. The vibratory frequency and the displacement amplitude were 20 kHz and 20 μm, respectively. In design of experiments, four various cavitation behaviors have been studied based on four cavitation test conditions corresponding to those behaviors. These conditions can be summarized as follows: (1) the usage of water as a testing liquid; (2) replacement the water with 3.5% NaCl solution; (3) applying a certain voltage to cause a combined electrochemical action working simultaneously with the water; and (4) applying the same voltage by using the 3.5% NaCl solution instead of water. The obtained results showed that the mass loss differs by test modes applied.

Cracking induced tribological behavior changes for the HVOF WC-12Co cermet coatings

HVOF sprayed WC based cermet coatings have been widely used in industries as barriers against wear and hydrodynamic cavitation due to their high hardness and relatively high toughness. However, cracking of the coatings can occur during coating production or in service, which can reduce operational performances. It can be difficult to assess the performance impact due to cracks within the coating and as to whether the cracked coatings should be resprayed or removed from service. In this work, artificial cracks of different widths were introduced to liquid fuel HVOF sprayed WC-12Co coating through uniaxial tension of the coated steel substrate to assess the implications of such cracking. Tribological performances of the cracked coatings were examined using rubber wheel dry abrasion, ‘ball on disc’ sliding wear, and ultrasonic cavitation erosion. The results show that the crack deteriorates the abrasive wear resistance of the coating at the initial stage due to preferable mass loss at the cracks. However, after 30 min of abrasion, all the cracked coatings showed the same wear rate as compared to the non-cracked coating, with the abrasive wear resistance acting independent to the crack characteristics. Because the cracks could store wear debris and thus minimize the debris induced abrasion to the coating surface during sliding wear test, both improvement in wear resistance and reduction in coefficient of friction (COF) were detected in the cracked coatings. During the cavitation test, it was found that the mass loss of the specimen increased significantly (up to 75%)with crack width and density suggesting that the crack presence greatly deteriorated the cavitation resistance of the cermet coatings.

Advancing methodology to specify cavitation characteristic of screw-type centrifugal pumps

The research proposes a methodology of high-rate cavitation tests significantly decreasing testing period as well as increasing the accuracy of specifying a cavitation characteristic. To specify it, the tests without holding up consumption are conducted; however, at the pump inlet the rate to minimize pressure is increased. To decrease a test discrepancy, the data logging system is introduced. The research determines the high-rate pressure decreases without holding up consumption; it does not impact the accuracy to specify the cavitation characteristic and minimizes pump operation under the cavitation conditions diminishing erosive action. Automation significantly minimizes labour intensity during tests and improves the accuracy.

Cavitation Erosion Performance of Steel, Ceramics, Carbide, and Victrex PEEK Materials

Abstract Cavitation erosion has to be taken into consideration during material selection in many industrial sectors, e.g., offshore, marine, and oil and gas, in which components operate under severe working conditions. The cavitation erosion equipment, located at the University of Southampton, uses a vibratory apparatus to compare, rank, and characterize the cavitation erosion performance of materials. This article highlights some of the results obtained from industrial research (consultancy) work employing a Hielscher UIP1000hd 20 kHz ultrasonic transducer (Hielscher Ultrasonics GmbH, Teltow, Germany). The transducer is attached to a titanium horn to induce the formation and collapse of cavities in a liquid, creating erosion (material loss) of the specimen undergoing testing. The results from erosion cavitation testing (in accordance with ASTM G32-16, Standard Test Method for Cavitation Erosion Using Vibratory Apparatus (Superseded)) of two commercially available steels are presented herein and are shown to have less resistance to cavitation when compared to polyether(ether ketone), ceramic, and carbide materials. These materials are presented, along with Nickel 200, which was used to normalize the results. A plot of cumulative erosion versus exposure time was determined by periodic interruption of the test.

Experimental and numerical investigation of cavitation on Clark Y foil

The results of experimental investigation of cavitation in flow over Clark Y foil are presented. The cavitation test rig included a chamber with a blade profile fixed to the rotary disc that enabled to set different angles of attack. Working fluid was water at temperature 16°C. For different flow conditions (water velocity, pressure) the pictures of cavitating flow were taken and analyzed. The pressure at the inlet and outlet of the chamber were measured, as well as the value of volumetric flow rate. That enabled to determine the cavitation number for each case. The mechanism of cavitation structures appearance, growth and collapse was observed and described. The numerical simulation of cavitating flow was also performed by means of Open FOAM software with interphase Change Foam solver. Kunz cavitation model was chosen for calculations, with k-ω SST turbulence model. The assumption of isothermal, two–phase flow was made. The vapour areas appearance, their shapes and changes in time were described and compared with experimental results. The main features of cavitating flow were caught, but the further adjustment of cavitation model is recommended.

On Surface Topography and Microstructure in Cavitation Erosion Tests of Alloy 80 A

From practical and economic reasons for the design of components for Diesel engines, the selection of materials and/or heat treatments is essential to provide a high cavitation erosion resistance. This paper studies cavitation behavior of the Nimonic 80A alloy designed for execution of Diesel engine exhaust valves. The cavitation tests where done on an ASTM G32 -2010 compliant vibrating device with piezoceramic crystals.The metalographic examinations performed with optical microscope and electronic scanning microscopy revealed the microstructural changes occurring in the region of the cavitation affected material and the path of the crack propagation

Cavitation erosion of AISI1045 steel in polyacrylamide solutions

The control of experimental conditions is imperative in the study of cavitation characteristics in polymer solutions. First, qualification of steady-state physical properties should be acquired for a given polymer solution. Second, the approaches to keeping the physical properties stable should be incorporated into the process of cavitation tests. The present investigations contain two aspects involving the steady-state conditions of certain polymer solutions for long ageing times and for experimental processes, as well as cavitation erosion performance, in polymer additives. As far as polyacrylamide solution is concerned, the findings demonstrate that the critical ageing time of the steady-state viscosity occurs at various concentrations and temperatures; viscosity is almost constant throughout the course of the vibratory tests, with a solution circulatory system attached. Based on viscosity stability, cavitation erosion of AISI1045 steel performs with good regularity and decreases with the increase of concentration as well as the decrease of temperature.

Cavitation Erosion Resistance and Wear Mechanism Model of Flame-Sprayed Al2O3-40%TiO2/NiMoAl Cermet Coatings

This manuscript deals with the cavitation erosion resistance of flame-sprayed Al2O3-40%TiO2/NiMoAl cermet coatings (low-velocity oxy-fuel (LVOF)), a new functional application of cermet coatings. The aim of the study was to investigate the cavitation erosion mechanism and determine the effect of feedstock powder ratio (Al2O3-TiO2/NiMoAl) of LVOF-sprayed cermet coatings on their cavitation erosion resistance. As-sprayed coatings were investigated for roughness, porosity, hardness, and Young’s modulus. Microstructural characteristics of the cross section and the surface of as-sprayed coatings were examined by light optical microscopy (LOM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) methods. Coating cavitation tests were conducted in accordance with the ASTM G32 standard using an alternative stationary specimen testing method with usage of reference samples made from steel, copper, and aluminum alloys. Cavitation erosion resistance was measured by weight and volume loss, and normalised cavitation erosion resistance was calculated. Surface eroded due to cavitation was examined in successive time intervals by LOM and SEM-EDS. On the basis of coating properties and cavitation investigations, a phenomenological model of the cavitation erosion of Al2O3-40%TiO2/NiMoAl cermet coatings was elaborated. General relationships between their properties, microstructure, and cavitation wear resistance were established. The Al2O3-40%TiO2/NiMoAl composite coating containing 80% ceramic powder has a higher cavitation erosion resistance than the reference aluminium alloy.