Cavitation Resistance Research Articles

Study of the cavitation resistance of Sn-based coatings

In this study, the resistance to cavitation erosion of different Sn-based journal bearing overlay coatings were studied and compared. An ultrasonic horn set-up was used to generate cavitation over the surface of samples coated with the evaluated coatings, the volume loss during the tests was estimated and the surface morphology and structure of the overlay coatings was investigated after tests. The results show how the overlay coating structure has an effect on the cavitation resistance of the Sn-based coatings studied, as the multilayered Sn-based overlay coating exhibited a significantly enhanced resistance to cavitation erosion compared with monolayered Sn-based overlay coatings.

Effect of erosion angle and Fe2B orientation on cavitation erosion and interfaces of Fe-B alloy in high-velocity flowing zinc

The effects of erosion angle and Fe2B orientation on cavitation erosion and interface structures of a directionally solidified (DS) Fe-B alloy in flowing liquid zinc were investigated to clarify erosion mechanism of liquid metal. The results indicate that the cavitation erosion rate of DS Fe-B alloy with Fe2B [001] orientation vertical to interface exhibits better erosion cavitation resistance. Erosion angle can strongly affect erosion performance that depends not only on interfacial orientation structure but also on local microturbulence. Erosion morphologies manifest that an obvious cavitation erosion occurs in strong flowing zinc disturbed and agitated zone, which results in severe cavitation pits and slip deformation of products, thus stimulating subsequent localized corrosion and pit-aggregation cracks. Cavitation erosion craters coupled with performance variations confirm that microturbulence-assisted fluid eddies and backflow are responsible for the cavitation pits. The combined effects of flow pattern and interface orientation significantly govern the epitaxial grown ζ removal/accumulation behaviors and multiphase pinning film adhesion. A model of hydraulic liquid-hammer action by cavitation-induced microjet and interface orientation interaction is proposed and discussed to account for cavitation pits and slip cracking, which reveals underlying erosion mechanism and material design of DS Fe-B alloy in flowing liquid zinc.

Microstructure and cavitation behaviour of alloyed austempered ductile irons

ABSTRACTIn this paper, the study of cavitation behaviour of austempered ductile iron (ADI) alloyed with copper, as well as copper and nickel with a fully ausferritic microstructure, is presented. The ADI materials used were austenitized at 900 °C and austempered at 350 °C having an ausferrite microstructure with 16 and 19% of austenite, respectively. The experimental investigations were conducted using the ultrasonically induced cavitation test method. The results show that the cavitation damage was initiated at graphite nodules, as well as in the interface between a graphite nodule and an ausferrite matrix. The cavitation rate revealed that the ADI material alloyed with Cu + Ni austempered at 350 °C/3 h has a higher cavitation resistance in water than ADI alloyed with Cu. An increased cavitation resistance of the ADI material alloyed with Cu and Ni is due to the matrix hardening by stress assisted phase transformation of austenite into the martensite (SATRAM) phenomenon.

Structure and cavitation erosion behavior of HVOF sprayed multi-dimensional WC–10Co4Cr coating

Abstract A new kind of multi-dimensional WC–10Co4Cr coating which is composed of nano, submicron, micron WC grains and CoCr alloy, was developed by high velocity oxy-fuel (HVOF) spraying. Porosity, microhardness, fracture toughness and cavitation erosion resistance of the multi-dimensional coating were investigated in comparison with the bimodal and nanostructured WC–10Co4Cr coatings. Moreover, the cavitation erosion behavior and mechanism of the multi-dimensional coating were explored. Results show that HVOF sprayed multi-dimensional WC–10Co4Cr coating possesses low porosity (≤0.32%) and high fracture toughness without obvious nano WC decarburization during spraying. Furthermore, it is discovered that the multi-dimensional WC–10Co4Cr coating exhibits the best cavitation erosion resistance which is enhanced by approximately 28% and 34%, respectively, compared with the nanostructured and bimodal coatings in fresh water. The superior cavitation resistance of multi-dimensional WC–10Co4Cr coating may originate from the unique micro–nano structure and excellent properties, which can effectively obstruct the formation and propagation of cavitation erosion cracks.

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A.mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A.mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes.

Influence of Particle Size Distribution on the Morphology and Cavitation Resistance of High-Velocity Oxygen Fuel Coatings

The cavitation wear process is one of the major wear mechanisms in turbines and rotors of hydroelectric power plants in Brazil. An effective way to increase the cavitation resistance is the use of coatings, applied by thermal spraying. The high-velocity oxy-fuel process (HVOF) is one of the most used thermal spraying processes, and it is widely adopted for applying coatings for protection against wear and in maintenance components. A FeCrMnSiB experimental alloy was deposited onto SAE 1020 substrate by HVOF process, in order to evaluate the influence of the powder particle size range on the morphology and cavitation resistance of the coatings. The morphology of the coatings showed an increase in oxide content with powder size reduction. The increase in the powder particle size reduced the wettability of the particles, observed by the increase in the quantity of non-melted particles. Higher particle size distribution led to an increase in erosion rate, due to higher presence of non-melted particles in the coatings and consequently reduction of splats adhesion. The cavitation damage was perceived mainly by the mechanism of lamellae detachment; however, part of the damage was also absorbed by strain hardening due to the γ-e martensitic transformation.

Investigation of cavitation erosion resistance of AlSi10Mg alloy for additive manufacturing

This study investigates the cavitation erosion resistance of AlSi10Mg additive manufactured samples according to the ASTM G32 standard, in comparison with the cast ones. Samples were tested in different conditions in order to analyse the effect of T6 heat treatment and hot isostatic pressing, while cast samples were studied in as-cast and heat-treated conditions. It was found that additive manufactured AlSi10Mg alloy shows outstanding cavitation erosion resistance, in comparison to the cast alloy, mainly due to the ultra-fine microstructure. This superior performance of as-produced AlSi10Mg additive manufactured samples was demonstrated by the extremely limited mass loss and erosion rate measured during the tests, coupled with a remarkably long incubation stage. On the other hand, the heat treatment proves detrimental to the cavitation resistance of additive manufactured material due to the microstructure modification and pores enlargement. Hot isostatic pressing only partially improves the alloy performance.

Is There Variability for Xylem Vulnerability to Cavitation in Walnut Tree Cultivars and Species (Juglans spp.)?

Drought-tolerance selection is a current challenge for breeding programs to ensure agrosystem resilience, particularly with intensity and frequency of drought increasing worldwide. In tree species, xylem vulnerability to cavitation is among the most important traits on which drought-induced mortality depends. It can be rapidly evaluated, enabling large-scale screening for drought resistance. Genetic variability and phenotypic plasticity for this trait have been studied in natural populations, but not yet for cultivated tree species. In this work, the genetic variability in xylem vulnerability to cavitation of six Persian walnuts (Juglans regia L.), six hybrid walnuts (J. regia × Juglans nigra), and seven walnut species was investigated. In the first step, the method for measuring xylem vulnerability to cavitation using the “Cavitron” centrifuge technique was improved on walnut samples to obtain more accurate results. The Cavitron technique was found well suited to assessing xylem vulnerability to cavitation on this species using a 0.38 m rotor, which is large enough to analyze samples with intact vessels. Despite differences in wood anatomical traits, xylem vulnerability to cavitation among the Persian walnuts studied was similar. Very narrow variations in xylem vulnerability to cavitation were also found among hybrid walnuts. Only slight differences were observed on comparing species among which some have shown differences in various traits. These results suggest uniform selection, leading to canalization in cavitation resistance for cultivated Juglans.

Adaptations of white spruce to climate: strong intraspecific differences in cold hardiness linked to survival.

Understanding local adaptation of tree populations to climate allows the development of assisted migration guidelines as a tool for forest managers to address climate change. Here, we study the relationship among climate, a wide range of physiological traits, and field performance of selected white spruce provenances originating from throughout the species range. Tree height, survival, cold hardiness, hydraulic, and wood anatomical traits were measured in a 32‐year‐old common garden trial, located in the center of the species range. Provenance performance included all combinations of high versus low survival and growth, with the most prevalent population differentiation for adaptive traits observed in cold hardiness. Cold hardiness showed a strong association with survival and was associated with cold winter temperatures at the site of seed origin. Tree height was mostly explained by the length of the growing season at the origin of the seed source. Although population differentiation was generally weak in wood anatomical and hydraulic traits, within‐population variation was substantial in some traits, and a boundary analysis revealed that efficient water transport was associated with vulnerable xylem and low wood density, indicating that an optimal combination of high water transport efficiency and high cavitation resistance is not possible. Our results suggest that assisted migration prescriptions may be advantageous under warming climate, but pronounced trade‐offs between survival and cold hardiness require a careful consideration of the distances of these transfers.

Cavitation resistance of surface composition "Steel-Ni-TiNi-TiNiZr-cBNCo", formed by High-Velocity Oxygen-Fuel spraying

The object of the study is a multilayered surface composition "Steel - a Multicomponent material with Shape Memory Effect - a wear-resistant layer" under conditions of cavitation effects in sea water. Multicomponent TiNi-based coatings with addition of alloying elements such as Zr in an amount up to 10% mass, allow to create a composite material with a gradient of properties at the interface of layers, which gives new properties to coatings and improves their performance significantly. The use of materials with shape memory effect (SME) as surface layers or in the composition of surface layered compositions allows to provide an effective reaction of materials to the influence of external factors and adaptation to external influences. The surface composite layer cBN-10%Co has high hardness and strength, which ensures its resistance to shock cyclic influences of collapsing caverns. The increased roughness of the surface of a solid surface composite in the form of strong columnar structures ensures the crushing of vacuum voids, redistributing their effect on the entire surface, and not concentrating them in certain zones. In addition, the gradient structure of the multilayer composite coating TiNi–Ti33Ni49Zr18–cBN-10%Co Co makes it possible to create conditions for the relaxation of stresses created by the variable impact load of cavitation caverns and the manifestation of compensating internal forces due to thermo-elastic martensitic transformations of SME materials. The cavitation resistance of the coating TiNi–Ti33Ni49Zr18–cBN-10%Co according to the criterion of mass wear is 15-20 times higher than that of the base material without coating and 10-12 times higher than that of the TiNi-TiNiZr coating. The proposed architecture of the multifunctional gradient composition, "steel-Ni-TiNi– Ti33Ni49Zr18–cBN-10%Co", each layer of which has its functional purpose, allows to increase the service life of parts operating under conditions of cavitation-fatigue loading in corrosive environments.

Improvement of cavitation resistance of composite films using functionalized alumina particles

Composite films having the UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as a matrix and the ferrous oxide doped alumina (Al2O3 Fe) based particles were prepared and subjected to cavitation. In order to improve the mechanical and adhesion properties of composites, four different surface modifications of filler particles were performed: 3-methacryloxypropyltrimethoxysilane (MEMO), vinyl-tris(2-methoxyethoxy)silane (VTMOEO), (3-aminopropyl)trimethoxysilane (APTMS) and biodiesel (BD). Composite films were made with 0.5, 1.5, and 3 wt.% of ferrous oxide doped alumina particles with each of the mentioned surface modifications. Composite films were prepared on brass substrates and exposed to cavitation erosion. The erosion was monitored using the mass loss while image analysis was used to observe surface defects. The composite film reinforced with Al2O3 Fe having VTMOEO as a surface modifier was the most resistant one in terms of mass loss, as well as the level of surface destruction. Results were compared to the same polymer matrix film and composite films prepared with fillers without surface modifications revealing that all composites with surface modified fillers exhibited some improvement in resistance to cavitation.

Evaluation of cavitation erosion resistance of Al-Si casting alloys: effect of eutectic and intermetallic phases

In the present paper, the influence of eutectic and intermetallic phases on cavitation resistance of Al-Si alloys was studied. In fact, Al-Si alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon. Samples of AlSi3, AlSi9 and AlSi9CuFe were characterized from the microstructural point of view. Hardness measurements were also performed. Subsequently, cavitation tests were carried out according to ASTM G32 standard and the erosion mechanism was examined by scanning electron microscope. It was found the both eutectic and intermetallic phases enhance cavitation resistance, expressed in terms of mass loss. Particularly, intermetallic particles with complex morphologies provide a positive contribution, exceeding that of other microstructural features, as grain size. The effect of T6 heat treatment was also evaluated. It was confirmed that the precipitation of fine strengthening particles in the Al matrix successfully hinders the movement of dislocations, resulting in a longer incubation stage and a lower mass loss for heat-treated samples in comparison with as-cast ones. Finally, the relationship between cavitation resistance and material hardness was investigated.

Adhesion testing of composites based on Bis-GMA/TEGDMA monomers reinforced with alumina based fillers on brass substrate

Abstract Quantitative assessment of the adhesion behavior between the composite film having UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as matrix and the aluminum oxide based particles as a reinforcement on metallic surface was done using the microhardness testing method and compared to the contact angle. Composites are made with 1 wt %, 3 wt %, 5 wt % and 10 wt % of alumina based fillers. Films were subjected to the cavitation in order to evaluate the erosion resistance of the composite film on the metal. It is proved that the adhesion is improved with addition of the fillers while the cavitation resistance is improved up to 5 wt % of fillers.

Influence of cobalt content and HVOF deposition process on the cavitation erosion resistance of WC-Co coatings

Cavitation is a wear process that occurs in aqueous environments in which water vapor bubbles on the metal surface of a component implode, leading to erosion. The phenomenon can cause significant damage to structural metal alloys, and many components are therefore covered with coatings to protect against this damage. Thermal spray coatings have long been used for this purpose. With the advent of the HVOF (high velocity oxy-fuel) spray process it became possible to produce denser, harder, tougher coatings, which can be used in applications where fracture toughness is more important. Among the materials most frequently used, tungsten carbide-cobalt (WC-Co) cermet coatings offer a combination of high hardness, toughness and adherence and consequent wear resistance. In this work, two WC cermets with different Co (binder) contents were used to investigate the influence of Co content on the fracture toughness and cavitation resistance of WC coatings deposited by the HVOF process using different fuels. The influence of the HVOF process (specifically the type of fuel used) on the residual stresses in these coatings and their microstructure and properties was also studied. An increase in Co content led to an increase in the fracture toughness and cavitation resistance of the coatings. The primary wear mechanism appears to involve carbide particles becoming detached from the Co matrix. The greater compressive residual stress when liquid fuel was used in the HVOF process resulted in improved properties, including fracture toughness, and a concomitant improvement in cavitation resistance.

Synthesis and characterization of porous tungsten carbide with added tungsten silicides

Porous materials made of commercial tungsten carbide (WC) with the addition of thermally obtained tungsten silicides (WSi2 and W5Si3) were made. The main research's contribution is firstly finding optimal conditions for synthesis tungsten silicides from elementary powders, and lately obtaining porous materials with excellent cavitation resistance. A phase transformation during synthesis of silicides was studied by changing temperature and time of heating. Obtained silicides were added to WC in different mass percentages. Mixtures were spark plasma sintered. Nanoindentation tests were performed on sintered samples, as well as cavitation erosion testing accompanied by measuring of mass changes and the profilometry measurements to scan the surface. Microstructure and morphology were determined by scanning electron microscopy (SEM), while porosity percentages based on SEM images were calculated by computer software QWin.

Microstructure and cavitation damage characteristics of surface treated gray cast iron by plasma ion nitriding

In this study, plasma ion nitriding (PIN) was performed as a measure to prevent the cavitation damage of gray cast iron (GCI) which is a cylinder liner material of diesel engine and evaluated its applicability. GCI treated by PIN presented about 45.2% improvement in surface hardness. In addition, a thickness growth behavior of flake-shaped graphite was observed in the nitrogen diffusion layer. As a result of cavitation erosion test, the maximum surface damage depth increased greatly due to a crater growth behavior along the depth on the flake-shaped graphite distributed on the surface. Furthermore, the weight loss after cavitation test indicated poorer cavitation resistance compared to the as-received specimen. Consequently, the application of PIN to prevent the cavitation erosion damage of GCI requires minimization of defects by flake-shaped graphite.

CFD based investigations for the design of severe service control valves used in energy systems

Multistage severe service control valves are extensively used in various energy systems, such as oil & gas, nuclear etc. The primary purpose of such valves is to control the amount of fluid flow passing through them under extreme pressure changes. As opposed to the conventional valves (butterfly, gate etc.), control valves are often installed in energy systems with geometrically complex trims, comprising of various geometrical features, formed by a complex arrangement of cylindrical arrays. The pressure within the trim varies in controlled steps and hence, cavitation resistance can be embedded in the trim through improved design process for the trim for severe service applications in energy systems. The flow characteristics within a control valve are quite complex, owing to complex geometrical features inherent in such designs, which makes it extremely difficult to isolate and quantify contribution of these features on the flow characteristics. One of the most important design parameters of such trims is the flow coefficient (also known as flow capacity) of the trim which depends on the geometrical features of the trim. The design of valves for particular performance envelop within the energy systems depends on effects of complex trim geometrical features on performance characteristics; hence, the focus of recent research is on quantifying the hydrodynamic behaviour of severe service control valves, including the trims. This includes the estimation of the local flow capacity contributions of the geometrical features of the trim through detailed numerical investigations. In this work, a tool has been developed that can be used to predict the local contribution of geometrical features on the flow coefficient of the trim. It is expected that this work will result in better performance of the energy systems where these valves are used.

Cavitation erosion behaviour of an innovative aluminium alloy for Hybrid Aluminium Forging

Aluminium alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon.In the present paper, the cavitation erosion resistance of an innovative light-alloy used for Hybrid Aluminium Forging was investigated. The material was tested by means of an ultrasonic vibratory device in compliance with ASTM G32. In order to better estimate the material behaviour, the same investigation was performed on two commercial alloys, 6061 wrought alloy and A356 casting alloy. The cavitation resistance of these materials was evaluated by determining the erosion rate from the progressive measurements of the samples mass loss during the test. The erosion mechanism was studied by means of optical and scanning electron microscope, and its correlation with the alloy hardness and microstructure was evaluated. The innovative alloy shows remarkable cavitation erosion resistance, particularly in heat-treated conditions.

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.

Effects of soil nutrient conditions on water transport properties and recovery from severe drought stress in Pinus densiflora saplings

ABSTRACTTo evaluate the acclimation of water transport properties to soil nutrient conditions, morphological and hydraulic traits were measured in 4-year-old potted saplings of Japanese red pine that were grown under differing nutrient conditions for 3 years. To compare recovery from severe drought stress under differing nutrient conditions, the well-watered saplings were subjected to drought treatments of almost Ψ50 by stopping irrigation; this is equivalent to the xylem water potential at which 50% loss of hydraulic conductivity occurs. After resuming daily watering, the xylem water potential and gas exchange rate were measured. Whole-plant transpirational demand from large total-leaf area tended to be high for plants under high-nutrient conditions. However, no differences were observed in water transport properties, such as the conducting area, hydraulic efficiency, and cavitation resistance, suggesting that acclimation of the hydraulic architecture did not occur when plants were grown under sufficient soil moisture conditions. The root dry weight tended to be large and the belowground dry mass to root dry mass (T/R ratio) tended to be low for plants under high-nutrient conditions. Plants grown under high-nutrient conditions recovered their gas exchange rate and leaf-specific hydraulic conductance slightly during the month following severe drought stress by irrigation. The recovery of Japanese red pine appears to vary under different levels of nutrient availability probably because of the influence of root water absorption capacity.