Ultrasonic Cavitation Test Research Articles

Differences in ultrasonic cavitation damage between new and used engine coolants with varying time in operation

This study investigates the cavitation erosion performance of heavy-duty engine coolants before and after operation in trucks using an ultrasonic test rig based on ASTM G32. Fresh coolants with 35% and 50% v/v glycol were compared with used coolants. One coolant was obtained from a gasoline-fueled vehicle with a mileage of 27000 km, and two from diesel-fueled vehicles with mileages of 16000 and 180 000 km, respectively. Surface tension and boiling point at atmospheric pressure were measured, a chemical analysis was carried out, and suspended particles were quantified by dynamic image analysis. The results showed that the used coolants caused a lower mass loss in ultrasonic cavitation testing than the fresh ones, and that they had higher boiling points, lower pH and a higher number of suspended particles, especially of those smaller than 30μm. Surface tension was higher for the used coolants from Diesel engines.The lower mass loss caused by all three used coolants can be attributed mainly to their high boiling point and high particle count. The presence of particles is believed to promote the heterogeneous nucleation of smaller, more stable bubbles, which may protect the exposed surface by shockwave absorption and microjet deflection. Some dissolved ions in the used coolants may help reduce their aggressivity by inhibiting bubble coalescence, reducing bubble collapse energy, despite increasing surface tension. Surface tension has complex interactions with the solutes, particles and bubble formation and cannot, in isolation, explain the differences in performance of the coolants.

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.

Influence of the deposition parameters on the tribological behavior of cold gas sprayed FeMnCrSi alloy coatings

Cold Spray deposition process may be an alternative for the High-Velocity Oxy-Fuel (HVOF), providing high kinetic energy without particles oxidation. In this work, an FeMnCrSi alloy was deposited onto carbon steel substrate by Cold Gas Spray (CGS) process varying spraying parameters (working gas, its pressure and temperature). Cavitation resistance was evaluated by ultrasonic cavitation testing, and the sliding wear resistance was studied by ball on disk testing, with intent to understand the behavior of this coating when exposed to sliding wear condition. FeMnCrSi sprayed using N2 working gas at 1000 °C showed higher hardness, elastic modulus, cavitation resistance, and sliding wear resistance than FeMnCrSi deposited with 900 and 1100 °C. The samples deposited with N2 at 1000 °C and He at 600 °C showed higher compressive residual stress and flatenning ratio also. The tests were performed for CGS sprayed 316 L stainless steel, which is used as a benchmark material.

Experimental study on the mesoscale causes of the effect of sediment size and concentration on material cavitation erosion in sandy water

The cavitation erosion of materials in sandy water is a very important topic in water conservancy and industrial production. In this paper, an ultrasonic vibration cavitation apparatus and underwater low-voltage electric discharge device are applied to investigate the erosion characteristics of 6063 aluminium specimens in sandy water with different sediment sizes and concentrations and the underlying mesoscale damage mechanism. The results show that the specimen damage gradually increases as the mean sand particle size increases. When the mean sand particle size is less than 0.120 mm, the resulting damage is lower than that in pure water. When the sand concentration is less than 10 kg/m3, the resulting damage is not very different from that in pure water. As the sediment concentration in the sand-water mixture increases, the influence of the sand particles on cavitation gradually increases. The bubble-particle interaction experiments reveal that the cavitation bubbles that interact with multiple small spherical particles show obvious non-spherical morphology and prolong the collapse time during the first collapse phase and reduce the collapse strength. The results of the bubble-particle interaction experiments verify the erosion characteristics obtained from the ultrasonic vibration cavitation test, which is significant for elucidating the damage mechanics of specimens in sandy water.

Assessment of flow aggressiveness and erosion damage topography for different gap widths in ultrasonic cavitation testing

Incubation time and erosion rate of C15 steel (SAE 1016) are measured in a cavitation test-rig utilizing an ultrasonic horn. The gap width (separation distance) between horn tip and stationary sample is varied and effects on material damage are studied. Cavitation erosion shows a local maximum for a gap width of 0.5 mm at the stationary specimen, while it continuously rises on the horn tip with rising gap width. A characteristic erosion pattern develops at horn tip and stationary specimen. By a-posteriori surface erosion topography measurements, radial erosion depth profiles are evaluated. Together with scanning electron microscopy investigations, they provide information on the spatial distribution of the flow aggressiveness and on wear mechanisms. By means of computational fluid dynamics (CFD) results, the local surface erosion topography is associated to harmonic and subharmonic collapse events within the gap. Pressure measurements have been performed by piezoelectric polyvinylidene fluoride (PVDF) sensors, mounted in central as well as eccentric position on the specimen surface. A local mean of the erosion depth profile is evaluated on the surface portion that corresponds to the PVDF sensor locations. By temporally high-resolved pressure data, a cumulative force load is evaluated. For larger gap width, a good correlation of cumulative force load with the inverse incubation time, erosion rate, as well as mean erosion depth is obtained, while for the smallest gap width of 0.3 mm, the correlation deteriorates.

Određivanje otpornosti na dejstvo kavitacije uzoraka pirofilita

The resistance under the action of cavitation of sintered pyrophillite samples was investigated. The initial sample of pyrophillite from the Parsovic-BiH deposit was ground a vibrating mill to a granulation of 20 mm, pressed and sintered at temperatures (⁰C): 100; 1100; 1200. To assess cavitation resistance, the change in sample mass as a function of cavitation time was monitored. The cavitation erosion test was performed using the ultrasonic vibratory cavitation test method according to the ASTM G-32 standard. Cavitation velocites were calculated for all samples, as a basic indicator of the resistance of the material under the action of cavitation. The change in the morphology of the surface with the test time was followed by scanning electron microscopy. Based on the values of cavitation velocity and analysis of the surface damage morphology, the cavitation resistance of the tested samples based on pyrophillite was determined. The obtained results indicate that the samples of sintered pyrophillite have satisfactory resistance to the action of cavitation and be applied in conditions of lower cavitation loads.

Damage mechanisms in cavitation erosion of nitrogen-containing austenitic steels in 3.5% NaCl solution

Interruptions of the passive layer of stainless steels by cavitation erosion expose the bare metal surface to the environment and can lead to cavitation-erosion-corrosion damage and synergistic effects. However, the probability for pitting corrosion is decreased during cavitation exposure of stainless steels in chloride solutions because mechanical passive film removal shifts corrosion potentials to lower cathodic values. In this study, the impact of 3.5 wt% NaCl in water on mass loss and damage features of two austenitic stainless N-containing steels is investigated to amend the understanding of cavitation erosion of passivating steels. Ultrasonic cavitation tests were carried out on steels 316LVM and CNMo0.95 in distilled water and 3.5% NaCl solution. Exposed surfaces were characterized qualitatively by light- and electron-microscopy and quantitatively by confocal microscopy. Damage mechanisms vary between the two steels but not with NaCl content in the solution. 316LVM also displayed the same mass loss in both solutions. CNMo0.95 possesses twice the strength as 316LVM, resulting in lower intensities of ductile damage mechanisms and slower damage progression. Mass loss of CNMo0.95 was lower in 3.5% NaCl solution compared to distilled water, which was primarily assigned to the effect of the salt content in the water on cavitation bubble formation.

Laser-assisted production of HAp-coated zirconia structured surfaces for biomedical applications

ObjectivesThe aim of this study was to develop a novel design for implants surface functionalization through the production of HAp-coated zirconia structured surfaces by means of hybrid laser technique. The HAp-rich structured surfaces were designed to avoid hydroxyapatite (HAp) coating detachment from the zirconia surface during implant insertion, thus guaranteeing an effective osseointegration. Materials and methodsThe functionalization process of zirconia surface started by creating micro-textures using a Nd:YAG laser and subsequent deposition of a HAp coating on the designated locations by dip-coating process. Afterwards, a CO2 laser was used to sinter the HAp coating. The potential of the HAp-coated zirconia structured surfaces was inspected concerning HAp bioactivity preservation, surface wettability, HAp coating adhesion to the textured surfaces and mechanical resistance of zirconia, as assessed by different approaches. ResultsThe functionalized surfaces exhibited a superhydrophilic behavior (2.30 ± 0.81°) and the remaining results showed that through the hybrid strategy, it is possible to maintain the HAp bioactivity as well as promote a strong adhesion of HAp coating to the textured surfaces even after high energy ultrasonic cavitation tests and friction tests against bovine bone. It was also verified that the flexural strength of zirconia (503 ± 24 MPa) fulfills the strict requirements of the ISO 13356:2008 standard and as such is expectable to be enough for biomedical applications. SignificanceThe promising results of this study indicate that the proposed surface design can open the window for manufacturing zirconia-based implants with improved bioactivity required for an effective osseointegration as it avoids the coating detachment problem during the implant insertion.

Cavitation erosion behavior of ceramic/organic coatings exposed to artificial seawater

The cavitation erosion damage of the materials in seawater is more severe than in freshwater due to the coupling effect of mechanical impact, instantaneous high temperature and seawater corrosion. This study reported that the ceramic/organic coating fabricated by the vacuum pressure impregnation epoxy resin into as-sprayed ceramic coating is introduced. The corrosion inhibition mechanism of the ceramic-based coatings in seawater after introducing the epoxy resin was further clarified. The influence of epoxy resin on the microstructure and mechanical properties of the ceramic coatings were systematically evaluated based on SEM, Vicker hardness and scratch results. The corrosion behaviors of the ceramic-based coatings with/without sealing treatment were evaluated by electrochemical corrosion tester. Their cavitation erosion performance in seawater was comparatively studied using the ultrasonic vibration cavitation testing machine. It was demonstrated by the experimental results that the hardness, compactness and cohesive strength of the ceramic/organic coatings were greatly improved compared with those of the as-sprayed ceramic coatings. The epoxy resin completely filled the defects of the ceramic coatings and effectively prevented the invasion of seawater. Accordingly, the anti-cavitation erosion of the ceramic/organic coatings was significantly improved.

Microstructure and cavitation erosion behavior of sputtered NiCrAlTi coatings with and without N incorporations

The NiCrAlTi coatings free of N and with N incorporations were deposited on austenitic stainless steel 304L by magnetron sputtering in Ar and in gas mixture of Ar and N2, respectively. The N incorporated in the coatings existed as nitride precipitates (from ∼3 vol.% to ∼17 vol.%) after vacuum annealing. All the NiCrAlTi coatings, whatever free of N or with N incorporations, exhibited better resistance against cavitation erosion than ion plating TiN coating and the substrate 304 L in ultrasonic cavitation tests. The NiCrAlTi coating free of N incorporation presents superior cavitation erosion resistance. However, the nitrogen incorporation within the NiCrAlTi coatings showed negative effects on the resistance against cavitation erosion.

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.

The influence of HVOF spraying parameters on the microstructure, residual stress and cavitation resistance of FeMnCrSi coatings

Thermal spray processes can be used to apply erosion-resistant coatings to components. One of the most important is the HVOF (High Velocity Oxygen Fuel) process, which is characterized by lower temperatures and higher projection velocities than arc and plasma thermal spray processes. This study sought to analyze the influence of three process parameters (standoff distance, fuel/oxygen ratio and powder feed rate) on particle velocity, particle temperature, coating microstructure and residual stress formation in FeMnCrSi coatings deposited by a liquid-fuel HVOF process and the effect in turn of coating microstructure and residual stress on coating cavitation resistance. An increase in fuel flow and reduction in standoff distance resulted in increased particle velocity but did not significantly affect particle temperature. Varying the process parameters had a significant influence on the residual stress in the coatings. A correlation between compressive residual stress, increased hardness and reduced mass loss rate during ultrasonic cavitation testing was observed.

Ti6Al4V laser surface preparation and functionalization using hydroxyapatite for biomedical applications.

This work presents a novel texture design for implants surface functionalization, through the creation of line-shaped textures on Ti6Al4V surfaces and subsequent sintering of hydroxyapatite (HAp) powder into the designated locations. HAp-rich locations were designed to avoid HAp detachment during insertion, thus guaranteeing an effective osseointegration. This process starts by creating textured lines using a Nd:YAG laser, filling these lines with HAp powder and sintering HAp using a CO2 laser. The adhesion of HAp is known to be influenced by HAp sintering parameters, especially laser power and scanning speed and also by the textured lines manufacturing. Different laser parameters combinations were used to assess the sintering and adhesion of HAp to the textured lines. HAp adhesion was assessed by performing high energy ultrasonic cavitation tests and sliding tests mimicking an implant insertion, with Ti6Al4V/HAp specimens sliding against animal bone. The HAp content retained after these tests was measured and results showed that an excellent HAp sintering and adhesion was achieved when using a scan speed of 1 mm/s and laser power between 9 and 9.6 W. It is important to emphasize that results indicated that the HAp bioactivity was maintained when using these conditions, validating this functionalization process for the production of hip prosthesis with improved bioactivity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1534-1545, 2018.

Analysis of the effect of impact of near-wall acoustic bubble collapse micro-jet on Al 1060

The bubble collapse near a wall will generate strong micro-jet in a liquid environment under ultrasonic field. To explore the effect of the impact of near-wall acoustic bubble collapse micro-jet on an aluminum 1060 sheet, the cavitation threshold formula and micro-jet velocity formula were first proposed. Then the Johnson-Cook rate correlation material constitutive model was considered, and a three-dimensional fluid-solid coupling model of micro-jet impact on a wall was established and analyzed. Finally, to validate the model, ultrasonic cavitation test and inversion analysis based on the theory of spherical indentation test were conducted. The results show that cavitation occurs significantly in the liquid under ultrasonic field, as the applied ultrasonic pressure amplitude is much larger than liquid cavitation threshold. Micro pits appear on the material surface under the impact of micro-jet. Pit depth is determined by both micro-jet velocity and micro-jet diameter, and increases with their increase. Pit diameter is mainly related to the micro-jet diameter and dp/dj≈0.95–1.2, while pit’s diameter-to-depth ratio is mainly negatively correlated with the micro-jet velocity. Wall pressure distribution is mostly symmetric and its maximum appears on the edge of micro-jet impingement. Obviously, the greater the micro-jet velocity is, the greater the wall pressure is. Micro pits formed after the impact of micro-jet on aluminum 1060 surface were assessed by ultrasonic cavitation test. Inversion analysis results indicate that equivalent stress, equivalent strain of the pit and impact strength, and velocity of the micro-jet are closely related with pit’s diameter-to-depth ratio. For the pit’s diameter-to-depth ratio of 16–68, the corresponding micro-jet velocity calculated is 310–370m/s.

Composite cavitation resistant PVD coatings based on NiTi thin films

As a protective coating, TiCN hard PVD coating was deposited on magnetron sputtered NiTi thin films under various coating architectures. The microstructure, composition, mechanical properties, tribological performance as well as the cavitation resistance of deposited coatings were analyzed by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), nanoindentation, ball–on-disc, scratch test, three dimensional (3D) optical microscopy, and the standard ultrasonic cavitation test (ASTM G 32). The obtained results revealed that under a specific coating architecture, the superelasticity of NiTi can be combined with high hardness and wear resistance of TiCN coatings. As a consequence of the combination of these properties, the composite NiTi based coatings are capable of presenting remarkable cavitation resistance and tribological performance.

Effect of Cold Work on Cavitation Resistance of an Austenitic Stainless Steel Coating

Machining procedures of welding deposits are usual and result on cold work hardened surfaces. The cold work effect on cavitation erosion of an austenitic stainless steel surface is assessed. FeCrMnSiB coatings were processed by PTA on AISI 304 plates. Specimens were grouped as the cold work deformed surface (CWHS) and the undeformed polished surface (UPS) specimens. Top surface and transverse section of coatings were analysed for slip lines and hardness changes by light microscopy and Vickers microhardness measurements. Ultrasonic cavitation tests were conducted in accordance to ASTM G32-10. CWHS specimens exhibited slip lines and hardened surfaces while UPS specimens did not show traces of slip lines and had insignificant changes on microhardness. Cold work prior to cavitation indirectly increased the nominal incubation time and reduced the maximum erosion rate. Cold work increases the duration of the acceleration period postponing the onset of the maximum erosion rate and enhancing cavitation resistance.

Influence of crystallographic orientation on cavitation erosion resistance of high interstitial CrMnCN austenitic stainless steels

The excellent resistance of high interstitial CrMnCN austenitic stainless steels to cavitation erosion was ascribed to strengthening by C+N and the low stacking fault energy causing improved resistance to fatigue and superior mechanical properties. Previous investigations revealed correlation of crystallographic orientation and cavitation erosion damage. In this study, different CrMnCN steels were investigated by ultrasonic cavitation testing. Results were correlated with indentation-derived properties. Alteration of the surface during cavitation was examined by scanning electron microscopy and electron back scatter diffraction. The investigations show influences of crystallographic orientation on the cavitation resistance of individual grains. A relationship between cavitation resistance and hardness and elastic indentation energy was derived in earlier research work. This study shows similar relationship for individual grains.

Evaluation of cavitation-induced pressure loads applied to material surfaces by finite-element-assisted pit analysis and numerical investigation of the elasto-plastic deformation of metallic materials

Implosion of cavitation bubbles close to a material applies a high pressure load on the surface that leads to cyclic, elasto-plastic deformation followed by damage and loss of material. The load strongly depends on the flow conditions and its experimental determination is extremely difficult. This study presents a method for quantitative calculation of the pressure loads induced by collapsing bubbles. This method is based on the analysis of pits on the material surface formed within the incubation period. The pits are footprints of collapsing bubbles and are measured by atomic force microscopy (AFM). An inverse algorithm based on finite element method (FEM) simulations is then used to determine the pressure load that is necessary to form the measured pits. The pressure fields, which are assumed to be axially symmetric (bell-shape profile), were calculated for cavitation pits formed in pure copper. The pits were induced by short-term exposure to cavitation in an ultrasonic cavitation testing device. Additionally, the elasto-plastic deformation of copper was numerically (FEM) investigated for a given cavitation load. It was found that the deformation is mostly elastic and that the maximum stress is located in a subsurface region. The maximum pressure of the cavitation load, the resulting maximum plastic strain in the material, and the ratio of the elastic to total deformation work correlate well with the ratio of pit width to pit depth. In order to evaluate the simplified assumption of a static pressure profile (bell-shape), the calculated pressure loads were critically compared to those determined by a detailed single bubble simulation with a compressible CFD flow algorithm. The maximum pressure profiles of the highly-transient CFD results show partly significant deviations dependent on the non-dimensional bubble stand-off distance to the wall. An improved pressure load profile and transient effects will be considered next in the FEM algorithm.

Experimental characterization of the nanoparticle size effect on the mechanical stability of nanoparticle-based coatings.

We present an experimental investigation of the mechanical stability of silica nanoparticle-based coatings as a function of the size of the nanoparticles. The coatings are built following a layer-by-layer procedure, alternating positive and negative surface charges. The mechanical stability of the multilayers is studied in water, on the basis of an ultrasonic cavitation test. The resistance of the coating to cavitation is found to remarkably increase with decreasing the size of the nanoparticles, indicating an increase of the cohesive energy density. The relative contribution of van der Waals and electrical double-layer interactions to the stability of the multilayer is discussed toward their size dependence.

Cavitation erosion and hydroabrasion resistance of cold work tool steels produced by powder metallurgy

Carbide-rich cold work tool steels produced by powder metallurgy are designed for applications that are exposed to heavy abrasive wear. Alloying with higher amounts of chromium and molybdenum additionally leads to corrosion resistance. This makes them excellent candidates for use in fluid flow systems with a high abrasive load, e.g. due to liquids containing sand particles. In this study, two different cold work tool steels were examined with focus on wear attack that may occur in combination with flowing liquids. On one hand, hydroabrasive attack results from fluids containing abrasives such as sand. This was simulated using a slurry pot containing a mixture of water and SiO2 particles. On the other hand, changes in flow speed may cause formation of cavitation bubbles that lead to erosive wear of the surfaces of nearby materials. Thus, despite the fact that resistance to surface spalling (e.g. by cavitation) was not a primary goal of alloy development, both alloys were also investigated by means of ultrasonic cavitation testing. The aim was to detect the influences of alloying system, processing route, and heat treatment condition on the wear resistance. The results indicate a positive influence of retained austenite on cavitation resistance, whereas the exact opposite holds true in the case of hydroabrasion. The damage mechanisms were analyzed by means of optical as well as scanning electron microscopy with special focus on the role of carbides during cavitation. Further attention was paid to the manufacturing route by comparing commonly used hot isostatic pressing (HIP) with supersolidus liquid phase sintering (SLPS). The latter permits consolidation of pre-alloyed powders to near net-shape parts or to thick protective layers on lower alloyed substrates. Compared to HIP, SLPS promises lower manufacturing costs combined with comparable mechanical properties.