Synergistic Erosion Research Articles

Empirical Study of the Effect of Nanocoolant Particles on Corrosion Rate of 316 Stainless Steel

The advancement of nanotechnology has had an impact on the use of heat exchangers. Nanocoolants, which offer higher thermal efficiency than traditional coolants, have paid significant attention. These innovative fluids, which contain nanomaterials, not only have better heat efficiency but also improve energy efficiency compared to regular coolants. However, the presence of solid nanoparticles in the coolant may cause corrosion and erosion of tubes, leading to massive degradation of those parts. To evaluate the effectiveness of nanocoolant particles, this research was conducted by studying the impact of using nanocoolant on erosion-corrosion occurring on metal surfaces. The study focused on the erosion-corrosion of stainless steel (AISI 316) in coolant solutions containing nanoparticles. The experiments utilized a rotating cylinder electrode (RCE) with rotational speeds ranging from 0 to 1800 rpm and a temperature range of 30°C-70°C. The corrosion rate was determined using the linear polarization resistance (LPR) method, while the erosion was measured by calculating the average surface roughness of the samples. The design of the experiment (DOE) was utilized to find the mathematical expressions of the effects of the nanocoolant on erosion and corrosion. The findings revealed that the corrosion rate and surface roughness of the samples increased with an increase in temperature and rotation speed. Furthermore, the erosion-corrosion effects of the nanocoolant were less significant in stagnant conditions than in flow conditions, and significant differences were observed when compared with conventional coolant. Additionally, synergistic erosion and corrosion processes were detected at higher temperatures and higher rotation speeds for both types of coolants.

Deal Size and Synergy Gains: A Case of Indian M&A

The article aims to estimate the relationship between synergy gains and deal size of mergers & acquisitions for Indian firms by examining deals that took place between 2005 and 2015. The paper employs principal component analysis to create a composite variable representing operating and financial synergy, followed by instrument variable 2SLS regression to estimate the relationship. The results suggest that small dealsize transactions do considerably better than large deals. The magnitude of financial synergy increases with deal size . However, large companies suffer substantial operating synergistic erosion.

Particle size distribution effects on cavitation erosion in sediment suspensions

Synergistic cavitation–particle erosion often occurs in high-speed sediment-laden flow in hydraulic structures and machines. However, erosion prediction is challenging due to the unclear relationship between erosion and the characteristics of sand- and silt-sized sediments, particularly the sediment particle size distribution (PSDS). In this study, vibratory erosion tests for carbon steel were conducted in suspensions of continuously graded sand–silt mixtures, and the influence of PSDS characteristics, such as the number of modes and sand-to-silt ratios, was investigated. The results indicated that both the total sediment concentration and PSDS parameters had a major impact on synergistic erosion. The changes in the PSDS patterns resulted in different erosion behaviors, even when the sand and silt concentrations were fixed. Based on the viscosity-enhancing effects of silt particles and the impinging effects of sand particles, a new theoretical model for determining the particle impact energy was developed by incorporating PSDS. A deeper understanding of the influence of PSDS and the application of the PSDS-based model can help predict and prevent synergistic erosion.

Effects of sediment diameter and concentration on cavitation characteristics and mechanism

The synergistic erosion caused by cavitation and abrasion is a common and severe problem for hydraulic machinery. In order to explore the mechanism of particles size and concentration effect on cavitation, taking the rotating disk as the research object. The solid-liquid-gas three-phase flow was calculated based on the non-homogeneous multiphase flow model, modified RNG k−εturbulence model, and ZGB model. The increase of particles size firstly inhibited the bubbles (0.02 mm ≤ d ≤ 0.1 mm) and then promoted the bubbles (0.1 mm <d ≤ 0.4 mm); When 0.27 mm < d ≤ 0.4 mm, both cavitation area and cavitation damage intensity are more significant than those of cavitation alone. When d = 0.1 mm, 1% ≤ Cv ≤ 10%, the increase of particles concentration promotes bubbles. However, that only enhances the cavitation area, but has little effect on the cavitation damage intensity. When particles severely inhibit the bubbles, the vortex rotation effect is the strongest, and the mainstream promotion and re-entrant jet inhibition effect are the strongest. The purpose of this paper is to provide some theoretical basis for exploring the mechanism of synergistic erosion.

Effect of Manganese on Synergistic Erosion–Corrosion Characteristics of A890 7A Hyper Duplex Stainless Steels

Effect of Manganese on Synergistic Erosion–Corrosion Characteristics of A890 7A Hyper Duplex Stainless Steels

Influence of solids motion on ultrasonic horn tip erosion in solid–liquid two-phase flows

Ultrasound technology is a promising technique for wastewater treatment. However, its industrial application and scale-up face numerous problems, such as ultrasonic horn tip erosion. In solid–liquid flow systems, the synergy between cavitation and solid particle erosion is unclear, and the influence of solids motion is relatively unknown. By analyzing the tribosystem near the tip surface, we hypothesize that the synergistic erosion depends on the flux of solid particles flowing past the surface, relating to the local solids concentration and velocity. This hypothesis was investigated by ultrasonic cavitation–particle erosion tests performed in an eccentrically agitated tank. To study the effect of local concentrations and velocities, we carefully controlled the total solids and impeller speeds by integrating their coupled influence. Results indicate that synergistic erosion was aggravated at higher solids concentrations and velocities, and both parameters, based on a sensitivity analysis, show similarities in their relative degree of influence on erosion. This supports our hypothesis, which unifies the two parameters into a single factor, and explains the synergism in solid–liquid flows. Understanding these influencing factors and mechanisms will contribute to erosion prediction and the optimization of ultrasound applications in wastewater treatment processes.

Dual role of microparticles in synergistic cavitation–particle erosion: Modeling and experiments

The synergy between cavitation erosion and solid particle erosion fascinates tribologists owing to the contradicting roles of microparticles in aggravating or alleviating erosion. Based on an effective-medium approach, we develop a theoretical model to predict synergistic erosion, which incorporates the influence of suspension viscosity on bubble/particle dynamics and the impact energy of erosive particles. The model was experimentally validated, with strong agreement between the model predictions and experimental results. Further analysis shows that the viscous effect of silt-sized particles (STPs, <50 μm) could mitigate or even override the impact of impinging micro-jets and sand-sized particles (SDPs, >50 μm). The critical sand-to-silt ratio—the SDP/STP ratio that results in the same material removal as that in the solids-free case—is found to be a key parameter in the prediction of the synergistic erosion. The model embodies the opposing effects of microparticles on the cavitation erosion, and shows promise for erosion prediction and prevention.

Synergistic erosion–corrosion behavior of X80 pipeline steel at various impingement angles in two-phase flow impingement

The purpose of this investigation was to document and understand the erosion corrosion of X80 pipeline steel under different angles of attack in two-phase flow impingement. The erosion corrosion behavior of X80 pipeline steel was studied by using sand jet. The weight loss, surface morphology and electrochemical performance of X80 pipeline steel under different angles of impact (30°, 45°, 60°, 75°, 90°) were studied at 12 m/s flow rate. The synergistic mechanism of erosion corrosion of X80 pipeline steel under different environment was analyzed. The experimental results show that the weight loss of the sample in pure water increased with the decrease of the impact angle. The weight loss of the sample in the sodium chloride solution decreased first and then increased with the decrease of the impact angle, reaching a minimal value at 60° impact angle. Positive synergy was observed at all impact angles, and synergy was most significant when the impact angle was 90°. The samples impacted at 30° showed the best corrosion resistance by electrochemical measurement. The corrosion resistance of the sample was consistent with the synergistic effect.

Effects of silica sand on synergistic erosion caused by cavitation, abrasion, and corrosion

In order to study the effects of silica sand on synergistic erosion caused by cavitation, abrasion, and corrosion, vibratory experiments were conducted on ASTM 1045 carbon steel specimens subjected to six particle sizes (0.01–0.1 mm) mixed in nine concentrations (6–300 kg/m3) with tap water or with six concentrations of NaCl (0.5–15%). The experimental results indicate that sand particles larger than 0.04 mm at concentrations of 30–150 kg/m3 increasingly aggravated synergistic erosion with increasing sand particle size and concentration. The difference was observed for sand particles smaller than 0.04 mm: these sands inhibited cavitation erosion at concentrations of 30–300 kg/m3, but aggravated erosion at concentrations of 6–30 kg/m3; the maximum erosion occurred at a concentration of 12 kg/m3. As the concentration of NaCl increased, the erosion due to cavitation and corrosion increased sharply before growing stable above a NaCl concentration of 3.5%. The synergistic erosion caused by cavitation, abrasion, and corrosion was more severe than the erosion in tap water or cavitation-corrosion in a 3.5% NaCl solution, demonstrating that sand has an aggravated effect on synergistic erosion.

Synergistic Erosion–Corrosion Behavior of X-65 Carbon Steel at Various Impingement Angles

A slurry impingement rig containing 6 wt.% SiO2 particles was used to investigate synergistic erosion–corrosion behavior of X-65 carbon steel at various impingement angles. Maximum erosion–corrosion and erosion rates occurred at impingement angles of about 25 deg and 40–55 deg, respectively. The synergy value highly depended on the impingement angle. The formation of patches of porous corrosion product followed by the formation of corrosion pits led to a positive synergy under impingement angle of 25 deg. At higher impingement angles, the absence of pits probably due to the formation of a more durable tribocorrosion layer resulted in a negative synergy.

Synergistic Erosion and Corrosion Behavior of AA5052 Aluminum Alloy in 3.5 wt% NaCl Solution Under Various Impingement Angles

Erosion–corrosion behavior of AA5052 aluminum alloy was studied in 3.5 wt% NaCl solution containing silica sand as erodent particle. The tests were carried out according to ASTM G119-09 standard using a slurry jet apparatus at a jet velocity of 3 m/s, sand concentration of 90 g/l, and various impingement angles of 25°–90°. The pure erosion rates were also obtained using cathodic protection of the samples during erosion–corrosion tests. Results showed that maximum pure erosion and erosion–corrosion rates occurred at impingement angle of 30°. On the other hand, a negative synergism rate was obtained under all conditions tested. Energy dispersive spectrometry analysis suggested that the negative synergism could be attributed to the existence of a protective oxide layer formed on the eroded surface of the samples during erosion–corrosion tests. Results also showed that corrosion rates during flow corrosion (i.e., no sand) and erosion–corrosion were much higher than the pure corrosion rate in a stagnant condition. Furthermore, there almost was no change in the corrosion rates at various impingement angles of 25°–90°. Scanning electron micrographs showed erosion features like raised lips and wear tracks at the impingement angle of 30°, and plastic deformation due to particle impact at the impingement angle of 90°.

Synergistic erosion–corrosion behavior of Al–brass alloy at various impingement angles

Erosion and erosion–corrosion behaviors of the Al–brass alloy were investigated using a slurry impingement rig at a velocity of 6m/s under impingement angles ranging from 20° to 90°. The maximum erosion and erosion–corrosion rates occurred at an impingement angle of 40°. The results showed positive synergisms at all impingement angles. The rate of erosion enhanced by corrosion showed values up to 54% of the total erosion–corrosion rate. Polarization curves showed a passive behavior in the stagnant condition. No passivation was observed in the flow and erosion–corrosion conditions indicating low durability of protective layers on the Al–brass alloy at jet velocity of 6m/s.

Synergy of cavitation and slurry erosion in the slurry pot tester

Hydraulic machine materials are routinely tested under laboratory conditions to study the effects of slurry erosion and cavitation erosion. The material removal may occur by either of the modes or by their combined effect. To evaluate the damage in the latter case, where the damage can be severe, there is a need for a suitable test method that combines the two modes. With this objective, a new simple method is developed that combines the effect of slurry erosion and cavitation erosion. Triangular prismatic bluff bodies are used as cavitation inducers in the conventional slurry pot tester. In the slurry pot the brass test specimens are exposed to water/slurry, with and without cavitation inducers. Analysis of the wear results reveals significant variations in material loss confirming synergistic erosion damage. The new laboratory testing method can be very useful in assessing and ranking of the material performance under combined particle and cavitation erosion conditions.

Molecular dynamics simulations of synergistic erosion of amorphous hydrocarbon films

The erosion of amorphous hydrocarbon films by bombardment with argon ions and simultaneous exposure to thermal atomic hydrogen is studied as a function of ion energy and hydrogen/argon flux ratio by molecular dynamics simulations using a reactive hydrocarbon potential and compared with experimental data. While erosion due to energetic argon only is dominated by physical sputtering, the additional presence of atomic hydrogen leads to a marked increase of erosion. The erosion yield increases with both hydrogen/argon flux ratio and energy. A mechanism has been identified which explains the experimentally observed increase of the sputtering yield for simultaneous bombardment: the surface erosion induced by momentum transfer processes is enhanced by screening effects of the additionally offered hydrogen in the near-surface region.

Erosion of POSS-polyimide films under hypervelocity impact and atomic oxygen: The role of mechanical properties at elevated temperatures

Low Earth orbital debris impacts on the external surfaces of satellites have increased dramatically in recent years. Polyimides are used as the outer layer of thermal control insulation blankets, covering most of the external spacecraft surfaces that are exposed to the space environment. A recently developed material, named polyhedral oligomeric silsesquioxane (POSS)-polyimide, shows significant enhancement in withstanding the space environment. In this work, the combined effect of ground-simulated hypervelocity space debris impacts and atomic oxygen (AO) on the erosion of POSS-containing polyimide films was investigated. During such hypervelocity impacts, elevated temperatures, on the order of hundreds degrees, are formed. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km s −1. The impacted films were exposed to an oxygen RF plasma environment, simulating the effect of AO in the low Earth orbit. Impacted polyimide films exposed to AO revealed synergistic erosion effect, while impacted POSS-containing samples showed improved erosion resistance. The increased erosion rate of the impacted polyimide film is explained by formation of residual stresses that affect the oxidation mainly by increasing the diffusivity of oxygen into the subsurface layers. Mechanical properties of the POSS-containing samples performed at 450 °C and fractographic examination supports the above hypothesis.

Synergistic erosion process of hydrocarbon films: a molecular dynamics study

Fundamental processes leading to the erosion of hydrocarbon films due to energetic argon ions and hydrogen atoms have been investigated using molecular dynamics simulations. A generic mechanism has been identified for carbon erosion due to energetic (150 eV) argon ions in the presence of sub-eV hydrogen atoms. This surface erosion process, which we call hydrogen enhanced physical sputtering (HEPS), is primarily a physical sputtering mechanism, enhanced due to the screening effect of hydrogen atoms. The energetic argon ions create open bonds within their penetration range. The hydrogen atoms passivate the open bonds created within the first few atomic layers. Subsequent ion bombardment causes the breaking of C–C bonds within and beyond the H penetration range. The steric effect of H atoms bound to the top layer of carbon atoms prevents the re-attachment of the broken bonds, and this leads to unsaturated molecule emission from the surface. The kinetic energy of the emitted molecules is above thermal energy and the emission takes place within 5 ps after the ion impact.

The difference between synergistic erosion–corrosion and corrosion of mild steel in SiC suspension

The synergistic erosion–corrosion and corrosion characteristics of mild steel were studied by using rotating disk apparatus and immersing in 0.05 wt.% SiC suspension, respectively. The difference between cavitation erosion and corrosion was determined by scanning electron microscope (SEM), positron annihilation lifetime spectra (PALS) and X-ray photoelectron spectroscopy (XPS). It was found that the propagation of cracks in pit area induced by cavitation erosion did not appear in the course of corrosion. The PALS results showed that the size and number of vacancy cluster induced by cavitation erosion was much larger than that induced by corrosion damage. The results of core level band spectra indicated that there were chemical shifts in the case of cavitation erosion and no chemical shifts except 40 min corrosion in immersion process. The results of valence band spectra implied that the oxidation of mild steel induced by cavitation erosion was more than that induced by corrosion damage.

Modification of a 5-eV Atomic-Oxygen Laser Detonation Source

The present work describes the modification of a commercial pulsed laser detonation source, used for simulating the low Earth orbit 5-eV atomic-oxygen environment. In this facility the pulsed atomic-oxygen beam originatesfrom a plasma and is accompanied by high levels of vacuum-UV radiation. Thus, the exposure of materials to the atomic-oxygen beam is therefore an exposure to a combined atomic-oxygen and vacuum-UV environment creating synergistic erosion effects. A simple, low-cost system, based on the selective reflection of oxygen atoms, was developed in order to remove the vacuum-UV component from the atomic-oxygen beam. This system reflected about 50% of the original atomic-oxygen content. The vacuum-UV content in the reflected atomic-oxygen beam was reduced to 0.03% of its content in the original atomic-oxygen beam. Chemical changes occurring in Kapton HN and Tefzel (ethylene-tetrafluoroethylene copolymer) under vacuum-UV irradiation were used to prove that the reflected residual vacuum-UV radiation has no effect on the tested polymers.

Synergistic erosion of graphite due to simultaneous bombardment by C + and H +

The chemical sputtering of pyrolytic graphite due to simultaneous bombardment by C + and H + ions has been studied as a function of ion energies, relative fluxes and sample temperature. Combined bombardment by C + ions (1 and 3 keV) and 300 eV H + does not result in a significant increase in the hydrocarbon yield (i.e., Σ C i H j /H + ) over the H + -only case. On the other hand, for 100 eV H + ions, an increase of up to about ∼50% in the hydrocarbon yield was observed, as the Φ C + / Φ H + flux ratio was varied from about 0.01 to 0.05. Above this flux ratio, the surface damage caused by the energetic ions appears to saturate, and there is no further increase in hydrocarbon production. The effect of near-surface damage on hydrocarbon formation was also seen for He + +H + cobombardment.

Recent progress in understanding ion bombardment-induced synergism in the erosion of carbon due to multispecies impact

Multiparticle bombardment-induced synergism in erosion of materials has become a subject of major interest because of its relevance in two important technological developments of recent decades, viz., microelectronics and thermonuclear fusion. Synergistic effects may produce an enhanced erosion of chemically reactive materials (for example, Si, SiO 2, etc, in microelectronics, and C, TiC, etc, in fusion technology) when these are bombarded simultaneously by low energy (⩽1 eV) reactive atoms/molecules and either of energetic (100s to 1000s eV) ions, electrons, or photons. An enhanced erosion is desirable for etching processes in microcircuit fabrication, but it may lead to an undesirably high rate of impurities introduction into fusion plasmas. Results presented here relate only to ion-induced synergistic effects in the erosion of C when simultaneously bombarded by energetic (60 to 5000 eV) H + (D +) ions and sub-eV H° atoms. First results show that synergism may increase the erosion yield of C by factors of ⩾50 to ⩾100 over the yields (~5 × 10 −5 to 10 −3 CH 4/H° due to sub-eV H° bombardment alone, or by factors of ~2 to 3 over the yields (~0.1 CH 4/H +) due to H +−C interaction at the temperature for maximum chemical erosion. Experiments and phenomenological models suggest that ion bombardment-induced damage may play a fundamental role in synergistic erosion.