Synergistic effect of ultrasonic cavitation erosion and corrosion of WC-CoCr and FeCrSiBMn coatings prepared by HVOF spraying

A Review of Cavitation Erosion on Pumps and Valves in Nuclear Power Plants

The cavitation erosion failure of pumps or valves induces the low efficiency and reduced service life of nuclear reactors. This paper reviews works regarding the cavitation erosion of pumps and valves in the nuclear power industry and academic research field. The cavitation erosion mechanisms of materials of pumps and valves are related to the microstructure and mechanical properties of the surface layer. The cavitation erosion resistance of austenitic stainless steel can be ten times higher than that of ferritic steel. The cavitation erosion of materials is related to the hardness, toughness, and martensitic transformation capacity. Erosion wear and erosion-corrosion research is also reviewed. Erosion wear is mainly influenced by the hardness of the material surface. Erosion-corrosion behavior is closely connected with the element composition. Measures for improving the cavitation erosion of pumps and valves are summarized in this paper. The cavitation erosion resistance of metallic materials can be enhanced by adding elements and coatings. Adhesion, inclusion content, and residual stress impact the cavitation erosion of materials with coatings.

Effect of 3.5 % NaCl solution with different Na2S concentrations on ultrasonic cavitation erosion behaviors of HVOF sprayed WC-Ni coatings

In this article, the WC-10Ni coatings were fabricated by HVOF spray, then the ultrasonic cavitation erosion performances of the coatings in distilled water and 3.5 wt% NaCl solution with various Na2S concentrations (0, 20 and 200 ppm) were investigated. The results of the cumulative volume loss of the coating in different mediums showed that the coating exhibited enhanced cavitation erosion resistance with the increase of Na2S concentrations in medium. The reason for the improvement on the cavitation erosion performance was the growth of corrosion product films containing sulphide. In comparison with the coating after cavitation erosion in medium without Na2S, no large craters and deep grooves were observed on the eroded coating surface in medium with Na2S. The ultrasonic cavitation damage of the coating manifests as the spall of the metal binder phase (Ni) and exposure of the hard phase (WC).

In situ measurement of cavitation damage from single bubble collapse using high-speed chronoamperometry

We quantitatively study cavitation damage non-invasively, in-place and time-resolved at microsecond resolution. A single, laser-induced bubble is generated in an aqueous NaCl solution close to the surface of an aluminum sample. High-speed chronoamperometry is used to record the corrosion current flowing between the sample and an identical aluminum electrode immersed in the same solution. This configuration makes it possible to measure the cavitation damage in the nanometer thin passive layer of the aluminum surface via the corrosion current from the repassivation. Synchronously with the corrosion current, the bubble dynamics is recorded via high-speed imaging. Correlation between the two measurements allows contributing cavitation damage to the respective stages of the bubble dynamics. The largest cavitation-induced currents were observed for the smallest initial bubble-to-surface stand-off distances. As the bubble re-expands and collapses again in several stages, further current peaks were detected implying a sequence of smaller damage. At intermediate stand-offs the bubble was not damaging and at large stand-off distances, the bubble was only damaging during the second collapse which again occurs at the solid surface.

Review of Novel High-Entropy Protective Materials: Wear, Irradiation, and Erosion Resistance Properties

By their unique compositions and microstructures, recently developed high-entropy materials (HEMs) exhibit outstanding properties and performance above the threshold of traditional materials. Wear- and erosion-resistant materials are of significant interest for different applications, such as industrial devices, aerospace materials, and military equipment, related to their capability to tolerate heavy loads during sliding, rolling, or impact events. The high-entropy effect and crystal lattice distortion are attributed to higher hardness and yield stress, promoting increased wear and erosion resistance in HEMs. In addition, HEMs have higher defect formation/migration energies that inhibit the formation of defect clusters, making them resistant to structural damage after radiation. Hence, they are sought after in the nuclear and aerospace industries. The concept of high-entropy, applied to protective materials, has enhanced the properties and performance of HEMs. Therefore, they are viable candidates for today's demanding protective materials for wear, erosion, and irradiation applications.

Investigating the Water Jet Erosion Performance of HVOF-Sprayed WC-10Co Coatings on 35CrMo Steel Utilizing Design of Experiments

To enhance the surface of a material with the desired qualities for diverse applications in service, a variety of thermal and thermo-chemical surface treatment processes are used. Due to the high-velocity impact inherent in the process, high-velocity oxy-fuel (HVOF) spray is now frequently employed in industrial applications for its ability to generate a high-quality coating with appropriate hardness and low oxide content. In this investigation, a high-velocity oxy-fuel (HVOF) thermal spraying process was utilized to coat WC-10Co powders on a 35CrMo steel substrate. A water jet erosion test was also used to examine the substrate and coated samples’ erosion behavior. The erosion rate was systematically investigated using water jet variables such as the angle of impingement, water jet velocity, standoff distance, and erodent discharge. For the development of multiple regression models, experiments were performed utilizing the central composite rotatable design and the response surface methodology. The angle of impingement had the most impact on the rate of coating erosion, leading to the water jet velocity, standoff distance, and erodent discharge.

Cavitation Resistance of WC-10Co4Cr and WC-20CrC-7Ni HVAF Coatings

Machines operating in aqueous environments may be subjected to cavitation damage during operation. This study aims to evaluate the cavitation resistance of WC-10Co4Cr and WC-20CrC-7Ni coatings under cavitation erosion conditions with additional electrochemical effects. The coatings were deposited on AISI 1040 steel substrates using a high velocity air fuel thermal spray process. The microstructure of the coatings was observed by a scanning electron microscope, while their phase composition was analyzed using an energy-dispersive microanalysis system. In addition, the microhardness of the coatings and substrate was measured, and the surface topography of the eroded surface layers was observed using a 3D optical profilometer. The results revealed that the cavitation resistance of the WC-20CrC-7Ni coatings was better than that of the WC-10Co4Cr coatings. The observation of the structure and surface topography made it possible to identity the reasons for the differences between the cavitation resistance of both coatings: The WC-20CrC-7Ni coatings had a finer grain structure, lower pore density, and lower as-sprayed surface roughness. These differences, along with the presence of a high Cr and Ni content in the feedstock powder, that increased the coating corrosion resistance, contributed to improving the cavitation resistance and reducing the material loss of the WC-20CrC-7Ni coatings.

Damage Development on the Surface of Nickel Coating in the Initial Period of Erosion

The common occurrence of the phenomenon of cavitation in many industries and the multitude of factors affecting the resistance to cavitation erosion of used materials contribute to the search for methods and appropriate parameters of coating application that are able to minimize the effects of erosion. To determine the validity of the developed application parameters and the method used, cavitation studies and microscopic observations of the development of erosion during the cavitation test were carried out. There was a clear lack of incubation time and a linear increase in losses after 60 min of the test. Moreover, the damage observed during the test overlapped, widening the area of erosion and thus leading to damage to the integrity of the coating.

Evaluation of cavitation/corrosion synergy of the Cr3C2-25NiCr coating deposited by HVOF process

Wear processes are always present in components exposed to different work situations. Hydraulic turbines in electric power generation and ship propellers are good examples of components subject to wear and corrosion. One way to protect these components, for example, is the deposition of coatings by thermal spray processes. Indeed, there are several wear or corrosion mechanisms acting simultaneously, and the validation of the mechanisms separately, is not the best way to select the better material. When materials have passivation as protective mechanism against corrosion, the mass loss due erosion can affect the materials selection. This paper study the combined effect of the corrosion on the cavitation mass loss, as well as, the cavitation mass loss influence on the corrosion properties of a chromium carbide Cr₃C₂-25NiCr coating. Despite of the modification of the erosion mechanism on the cavitated samples under 3,5% NaCl solution, the volume loss did not show any significant alteration. Cavitation mass loss increase the corrosion process, reducing significantly the corrosion potential and raising the corrosion current. It was observed that the cavitation of the Cr₃C₂-25NiCr HVOF coating influences much more the corrosion kinetics, than the corrosion affects the cavitation resistance.

The Effects of Sand Particles on the Synergy of Cavitation Erosion-Corrosion of MIG Welding Stainless Steel Coating in Saline Water

Cavitation erosion (CE) is a common problem troubling many flow-handling equipment such as valves, orifice plate pipes, and propellers. The coating technique is a widely used strategy to resist CE. It is important to understand the CE-corrosion behavior of the coatings in the corrosive solution, especially in the sand-containing saline water. A newly designed MIG welding precipitated hardened martensitic stainless steel (PHMSS) coating was performed, and its silt-CE was investigated in a suspension composed of 3.5 wt.% sodium chloride and 3% silica sand using an ultrasonic vibrator processor. The microstructure of the coating was characterized by optical microscopy and scanning electron microscopy. The effects of the sand particles on the CE-corrosion were analyzed using mass loss measurement, potentiodynamic polarization curve, and surface morphology observation. The results showed that the PHMSS coating was mainly composed of the lath martensitic phase alone. Its mass loss rate was in ascending order in the solution of distilled water alone, sand-containing distilled water, saline water alone, and sand-containing saline water. Sand particles played more roles in the CE in the distilled water than in the saline water. The synergy of CE and corrosion was much less in the sand-free saline than in the sand-containing saline. The maximum component was the erosion enhancement due to the corrosion in the saline without sand particles but was the pure erosion component in the saline with sand particles. The mechanism of the sand particles' effect on the CE was also discussed.

Resistance of PVD Coatings to Erosive and Wear Processes: A Review

Due to the increasing maintenance costs of hydraulic machines related to the damages caused by cavitation erosion and/or erosion of solid particles, as well as in tribological connections, surface protection of these components is very important. Up to now, numerous investigations of resistance of coatings, mainly nitride coatings, such as CrN, TiN, TiCN, (Ti,Cr)N coatings and multilayer TiN/Ti, ZrN/CrN and TN/(Ti,Al)N coatings, produced by physical vapor deposition (PVD) method using different techniques of deposition, such as magnetron sputtering, arc evaporation or ion plating, to cavitation erosion, solid particle erosion and wear have been made. The results of these investigations, degradation processes and main test devices used are presented in this paper. An effect of deposition of mono- and multi-layer PVD coatings on duration of incubation period, cumulative weight loss and erosion rate, as well as on wear rate and coefficient of friction in tribological tests is discussed. It is shown that PVD coating does not always provide extended incubation time and/or improved resistance to mentioned types of damage. The influence of structure, hardness, residence to plastic deformation and stresses in the coatings on erosion and wear resistance is discussed. In the case of cavitation erosion and solid particle erosion, a limit value of the ratio of hardness (H) to Young’s modulus (E) exists at which the best resistance is gained. In the case of tribological tests, the higher the H/E ratio and the lower the coefficient of friction, the lower the wear rate, but there are also many exceptions.

Corrosion and material alterations of a CuZn38Pb3 brass under acoustic cavitation

An alloy that is exposed to cavitation may experience mechanical cavitation damages as well as accelerated corrosion. In the present paper, the evolution of corrosion erosion behavior of brass samples (CuZn38Pb3) during continuous exposure to ultrasonic cavitation in a salt solution (NaCl) was investigated. Various samples were sonicated for times between 0 min and 5 h. The average surface roughness and the effective surface area of the samples were measured by confocal microscopy, and the surfaces were inspected by scanning electron microscopy. Different erosion behavior of the phases present on the surface is discussed. Complementary to the surface inspection, the corrosion behavior of the samples before, during and after sonication was investigated through open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The results show that at the initial times of sonication preferably the lead islets were removed from the brass surface, resulting in a change in the open circuit potential. α and β' phases showed ductile and brittle behavior under sonication, respectively. The corrosion rate of the alloy under cavitation increased as the sonication time increased, mainly related to the increase in effective surface area and the rise of plastic deformation of the surface material.

Comparative Study of Jet Slurry Erosion of Martensitic Stainless Steel with Tungsten Carbide HVOF Coating

This work evaluates the behavior of a martensitic stainless steel (AISI 410) thermally treated by quenching and tempering with a tungsten carbide (86WC-10Co-4Cr) coating obtained by high-velocity oxygen fuel (HVOF) thermal spray deposition, analyzing the volume loss under erosive attacks at 30 ∘ and 90 ∘ incidence angles by using jet slurry erosion equipment with electrofused alumina erodent particles. Firstly, the characterization of the samples was carried out in terms of the microstructure (SEM), thickness, roughness, porosity, and microhardness. Then, samples were structurally characterized in the identification of the phases (XRD and EDS) present in the coating, as well as the particle size distribution (LG) and morphology of the erodent. It was determined that the tungsten carbide coating presented better resistance to jet slurry erosion wear when compared to the martensitic stainless steel analyzed, which is approximately two times higher for the 30 ∘ angle. The more ductile and brittle natures of the substrate and the coating, respectively, were evidenced by their higher volumetric erosion at 30 ∘ for the first and 90 ∘ for the latter, as well as their particular material removal mechanisms. The enhanced resistance of the coating is mainly attributed to its low porosity and high WC-Co content, resulting in elevated mechanical resistance.

Ultrasonic cavitation erosion mechanism and mathematical model of HVOF sprayed Fe-based amorphous/nanocrystalline coatings

A Fe-based amorphous/nanocrystalline coating was prepared on the AISI 321 steel by the high-velocity oxygen-fuel (HVOF) thermal spraying technology in this paper. Cavitation erosion behavior and mechanism of the coating was studied through the analysis of curves for cavitation erosion resistance versus time and the observation of eroded particles, with the AISI 321 steel as a reference. It was found that the Fe-based coating had better cavitation erosion resistance than the AISI 321 steel, and exhibited obvious periodic failure behavior in the cavitation erosion process. Besides, the crystallization of the amorphous phase under the effect of shock wave was observed. The cavitation erosion mathematic model of the coating was also established. The model indicated that the cavitation erosion resistance of the coating was related to the grain size and the fracture energy per unit area of the coating. Small grain size and high fracture energy per unit area were benefit to improve the cavitation erosion resistance of the Fe-based coating.

Enhancing the cavitation erosion resistance of D8m-Ta5Si3 nanocrystalline coatings through Al alloying

To investigate the effects of Al alloying on the erosion-corrosion resistance of β-Ta₅Si₃, both a β-Ta₅Si₃ coating and an Al-alloyed β-Ta₅(Si_0.83Al_0.17)₃ coating were synthesized on a 316 substrate by the double cathode glow discharge technique. The phase constitution, composition and microstructure of the two coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two coatings were composed of nearly rounded D8_m-β-Ta₅Si₃ grains with an average size of ∼4 nm, and after the addition of Al, the preferred growth orientation for the β-Ta₅Si₃ coating changed from (4 0 0) to (0 0 2). The hardness, elastic modulus and contact damage resistance of the coatings were measured using a nanoindentation tester. The results showed that Al alloying improved the contact damage resistance of β-Ta₅Si₃ with only a slight decrease in hardness. The erosion-corrosion behavior of the two coatings was performed in a 3.5 wt% NaCl solution containing a 12 wt% concentration of silica sand under two phase slurry flow condition and in a 3.5 wt% NaCl solution under ultrasonic cavitation erosion conditions. This revealed that the Al alloyed β-Ta₅Si₃ has a higher resistance to both erosion-corrosion and ultrasonic cavitation erosion as compared to the binary β-Ta₅Si₃ coating.

Effect of substrate preheating treatment on the microstructure and ultrasonic cavitation erosion behavior of plasma-sprayed YSZ coatings

Inconel 718 was used as the substrate and preheated at different temperatures to deposit yttrium stabilized zirconia (denoted as YSZ) coatings by atmospheric plasma spraying. The microstructure of the as-deposited YSZ coatings and those after cavitation-erosion tests were characterized by field emission scanning electron microscopy, Raman spectroscopy, and their hardness and toughness as well as cavitation-erosion resistance were evaluated in relation to the effect of substrate preheating temperature. Results indicate that the as-deposited YSZ coatings exhibit typical layered structure and consist of columnar crystals. With the increase of the substrate preheating temperature, the compactness and cohesion strength of coatings are obviously enhanced, which result in the increases in the hardness, elastic modulus and toughness as well as cavitation-erosion resistance of the ceramic coatings therewith. Particularly, the YSZ coating deposited at a substrate preheating temperature of 800 °C exhibits the highest hardness and toughness as well as the strongest lamellar interfacial bonding and cavitation-erosion resistance (its cavitation-erosion life is as much as 8 times than that of deposited at room temperature).

Microstructure and Cavitation Erosion Resistance of HVOF Deposited WC-Co Coatings with Different Sized WC

Conventional, multimodal and nanostructured WC-12Co coatings with different WC sizes and distributions were prepared by high velocity oxy-fuel spray (HVOF). The micrographs and structures of the coatings were analyzed by scanning electron microscope (SEM), X-ray diffractometer (XRD) et al. The porosity, microhardness and fracture toughness of the WC-Co coatings were measured. The coating resistance to cavitation erosion (CE) was investigated by ultrasonic vibration cavitation equipment and the cavitation mechanisms were explored. Results show that there is serious WC decarburization in nanostructured and multimodal WC-Co coatings with the formation of W2C and W phases. The nanostructured WC-Co coating has the densest microstructure with lowest porosity compared to the other two WC-Co coatings, as well as the highest fracture toughness among the three coatings. It was also discovered that the nanostructured WC-Co coating exhibits the best CE resistance and that the CE rate is approximately one-third in comparison with conventional coating.

Corrosion, Erosion and Wear Behavior of Complex Concentrated Alloys: A Review

There has been tremendous interest in recent years in a new class of multi-component metallic alloys that are referred to as high entropy alloys, or more generally, as complex concentrated alloys. These multi-principal element alloys represent a new paradigm in structural material design, where numerous desirable attributes are achieved simultaneously from multiple elements in equimolar (or near equimolar) proportions. While there are several review articles on alloy development, microstructure, mechanical behavior, and other bulk properties of these alloys, then there is a pressing need for an overview that is focused on their surface properties and surface degradation mechanisms. In this paper, we present a comprehensive view on corrosion, erosion and wear behavior of complex concentrated alloys. The effect of alloying elements, microstructure, and processing methods on the surface degradation behavior are analyzed and discussed in detail. We identify critical knowledge gaps in individual reports and highlight the underlying mechanisms and synergy between the different degradation routes.

A new methodology to prepare ceramic-organic composite coatings with good cavitation erosion resistance

A simple, scalable and economical method was proposed to obtain ceramic-organic composite coating with excellent comprehensive properties include hardness, toughness, elastic recovery, lamellar interfacial bonding and anti-cavitation erosion: introducing epoxy resin into the pores and micro-cracks of plasma sprayed ceramic coating. The results indicate that the epoxy resin was successfully penetrated into the whole ceramic coating and filled almost all defects by vacuum impregnation, which greatly enhanced its compactness and mechanical properties. The bonding strength between top coating and metal interlayer significantly increased from 17.3 MPa to 53.0 MPa, and the hardness (H) of top coating greatly increased from 11.07 GPa to 23.57 GPa. Besides, the value of H³/E² also increased from 0.06 GPa to 0.15 GPa, meaning the toughness of ceramic coating had been obviously improved. The pure ceramic coating had been punctured only after 4 h of cavitation test. However, the resin with high elasticity and toughness can effectively absorb impact energy, prevent cracks propagation and delay splats spallation during the cavitation erosion process. The novel composite coating displayed far better cavitation erosion resistance than pure ceramic coating, and it was still intact after 10 h of test.

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al_0.1CoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al_0.1CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA.

Effects of Power Ultrasound on Stability of Cyanidin-3-glucoside Obtained from Blueberry

Power ultrasound (US) could potentially be used in the food industry in the future. However, the extent of anthocyanin degradation by US requires investigation. Cyanidin-3-glucoside (Cy-3-glu) obtained from blueberry extracts was used as research material to investigate the effect of power ultrasound on food processing of anthocyanin-rich raw materials. The effects of ultrasonic waves on the stability of Cy-3-glu and on the corresponding changes in UV-Vis spectrum and antioxidant activity were investigated, and the mechanisms of anthocyanin degradation induced by ultrasonic waves were discussed. To explore Cy-3-glu degradation in different environments, we kept the Cy-3-glu solution treated with ultrasonic waves in four concentrations (0%, 10%, 20%, and 50%) of ethanol aqueous solutions to simulate water, beer, wine, and liquor storage environment according to the chemical kinetics method. Results show that the basic spectral characteristics of Cy-3-glu did not significantly change after power ultrasound cell crusher application at 30 °C. However, with anthocyanin degradation, the intensity of the peak for Cy-3-glu at 504 nm significantly decreased (p < 0.05). The degradation kinetics of Cy-3-glu by ultrasonic waves (200–500 W frequency) fitted well to first-order reaction kinetics, and the degradation rate constant of Cy-3-glu under power ultrasound was considerably larger than that under thermal degradation (p < 0.05). The sensitivity of the anthocyanins of blueberry to temperature increased with increasing ethanol concentration, and the longest half-life was observed in 20% ethanol aqueous solution.