Erosion Damage Research Articles

EROSION BEHAVIOR OF NICKEL DIFFUSION MEMBRANES IN CONDITIONS OF WATER ELECTROLYSIS

Preliminary studies of the erosion resistance of Ni diffusion membranes under the conditions of water electrolysis in various modes were carried out. Particular attention was paid to the time dependencies of the current, voltage and the electrolyte temperature during the process. Both electrodes, anode and cathode, were in the form of tubes of Ni-99.5 % wt. The electrolyte was pure drinking water after the filter with mineralization (ppm) 14, as well as water with the addition of sodium bicarbonate (mineralization 140...160 ppm). It is demonstrated that after several hours of operation cathodes showed no signs of erosion or other damages. The degree of erosion was assessed by weighing, and the state (morphology) of the surface was visually examined using an optical microscope. As for the anode, even when electrolyzing sufficiently pure water (ppm = 14), there is noticeable erosion and surface damage. To elucidate the reasons for such behavior of Ni electrodes, further studies are planned, in particular, using some other materials as an anode.

Experimental and numerical investigation of erosion in plugged tees for liquid-solid flow

Sand particle erosion is a prevalent issue that cannot be ignored in oil field development and may lead to leakage accidents. Consequently, it is significant to investigate and quantify erosion in pipelines. In this study, a flow loop is utilized to study the erosion of plugged tees in liquid‒solid flow. Then, computational fluid dynamics (CFD) software ANSYS Fluent is used to develop an erosion prediction numerical model, and the numerical erosion profile is validated with the experiments. Through particle trajectory analysis, three representative particle movement paths are selected, which provides a deeper understanding of erosion generation. Additionally, the erosion damage mechanism is analyzed through the surface morphology of the samples and particle impact behavior. The findings reveal that particles can follow the secondary flow to impact the inside of the downstream pipe under the experimental flow conditions. As the particle size or liquid velocity increases, the particles begin to erode the outside of the pipe under the action of inertial force. Due to the low-angle impact of the particles, the corresponding erosion damage mechanism is micro-cutting.

Dynamic Response of a SPAR-Type Floating Wind Turbine Foundation with Taut Mooring System

Compared with the traditional catenary or semi-taut mooring lines, the taut mooring system is more advantageous in many aspects, such as reduction of mooring line loads, erosion and fatigue damage during the powering productions of the floating wind turbines. This paper presents a taut mooring system made of synthetic fiber mooring lines, which can experience large elongations for a spar-type floating wind turbine. A finite element method (FEM)-based tensile mooring line model is proposed to study the mooring statics and dynamics of the floating wind turbine. A time domain modelling method coupled with the developed mooring line model is adopted to study the dynamics of a spar-type floating wind turbine foundation moored by the taut mooring system under regular waves. A systematic dynamic response and structural analysis are conducted based on variations in the mooring length and pretension. Additionally, comparative performance analyses are investigated for two mooring configurations with different numbers of mooring lines: two-point and three-point taut mooring system. It is found that factors, such as mooring length, pretension and the number of mooring lines, have significant impact on the in-plane and out-of-plane motion responses of the foundation.

Probing the Dynamic Progression of Erosion–Corrosion of X65 Pipeline Steel Using the Electrical Resistance Method in Conjunction with Galvanostatic Polarization

The initiation of erosion and the coupled damage of erosion and corrosion on the surface of X65 pipeline steel with varying applied anodic currents were online monitored using the electrical resistance (ER) method. Results show that ER method in conjunction with anodic polarization was a highly effective approach for the investigation of the interaction effect between erosion and corrosion, which can be used to quickly and conveniently obtain the synchronously changed erosion and corrosion rates. The critical impact energy is a key parameter of sand particles to induce erosion damage on the steel surface, which can remove the flaky cementite at the edge of the pits. The threshold anodic current density that can cause a synergic effect between erosion and corrosion of X65 pipeline steel can be quantitatively fitted based on the erosion rates under varying anodic currents.

Possibilities of measuring roughness with the probe contact method and promising methods for improving the process

One of the main operational properties of the product is the surface roughness. The presence of micro-dimensions and their size affect the strength, chemical resistance, abrasion and even the appearance of the product. But any real surface after metalworking acquires depressions and protrusions that are absent on a perfectly smooth surface. Therefore, the determination of surface roughness is one of the key parameters for metal products.Processes occur on the surfaces of parts that have a negative impact on them: the emergence of cracks, wear due to friction, erosion and corrosion damage, crumpling. Often such defects in materials have no less impact than deformation. The addition of certain microgeometric properties to the surface increases the resistance of the part to external influences and, as a result, increases strength and reliability. Therefore, the surface roughness parameters are of extremely important technical importance. In the course of research, the question of the variability of roughness on the surface of plexiglass from the effects of sandpaper of different grain sizes was investigated. The problem of scratches of plastic elements is very acute, especially when it comes to protecting the exterior of parts made of plexiglass and plastic. That is why a study was conducted showing the dependence of roughness on the sample of abrasive material

Anti-protein arginine deiminase antibodies are distinctly associated with joint and lung involvement in rheumatoid arthritis.

RA is a chronic inflammatory disease in which possible interstitial lung disease (ILD) is an extra-articular manifestation that carries significant morbidity and mortality. RF and ACPA are included in the RA classification criteria but prognostic and diagnostic biomarkers for disease endotyping and RA-ILD are lacking. Anti-protein arginine deiminase antibodies (anti-PAD) are a novel class of autoantibodies identified in RA. This study aimed to assess clinical features, ACPA and anti-PAD antibodies in RA patients with articular involvement and ILD. We retrospectively collected joint erosions, space narrowing, clinical features and lung involvement of a cohort of 71 patients fulfilling the 2010 ACR/EULAR RA classification criteria. Serum samples from these patients were tested for ACPA IgG (QUANTA Flash CCP3), and anti-PAD3 and anti-PAD4 IgG, measured with novel assays based on a particle-based multi-analyte technology (PMAT). Anti-PAD4 antibodies were significantly associated with radiographic injury (P = 0.027) and erosions (P = 0.02). Similarly, ACPA levels were associated with erosive disease (P = 0.014). Anti-PAD3/4 double-positive patients displayed more joint erosions than patients with anti-PAD4 antibodies only or negative for both (P = 0.014 and P = 0.037, respectively). RA-ILD (15.5%, 11/71 patients) was associated with older age (P < 0.001), shorter disease duration (P = 0.045) and less erosive disease (P = 0.0063). ACPA were elevated in RA-ILD, while anti-PAD4 were negatively associated (P = 0.043). Anti-PAD4 and anti-PAD3 antibodies identify RA patients with higher radiographic injury and bone erosions. In our cohort, ILD is associated with lower radiographic and erosive damage, as well as low levels of anti-PAD4 antibodies.

Active thermography for the interpretation and detection of rain erosion damage evolution on GFRP airfoils

Defects such as voids, which may occur during the manufacturing of wind turbine blades, have a significant impact on premature rain erosion, especially at the leading edge. Active thermography offers the potential for non-contact in-situ inspection of rotor blade leading edges. Thermographic investigations on curved and coated GFRP specimens have shown that sub-surface defects not only represent a susceptibility to erosion, but that the onset of erosion is dependent on the depth of the defects. Furthermore, the damage development of sub-surface towards surface defects can be visualized, which allows the damage stage to be assigned to an erosion stage.

Comprehensive assessment of the durability deterioration of asphalt pavement in salt environment: A literature review

With the increasingly extensive application of road engineering, it is inevitable to consider the durability of pavement in harsh environment. In the southeast coastal areas, northwest salt lakes and saline soil areas of China, harsh natural climate conditions and enhanced salt have a significant negative impact on the service life of asphalt pavements. In addition, the durability of asphalt pavement has suffered irreparable harm of the man-made salt environment. In this paper, five typical salt environment characteristics of asphalt pavement has been analyzed. The experimental conditions affecting the durability of asphalt concrete are determined. Then the durability deterioration mechanism of asphalt concrete is discussed under the coupling action of salt and multiple factors. Subsequently, the evaluation methods of asphalt concrete are categorized and summarized using scales for road performance and structure. Finally, according to the degree of salt erosion damage of asphalt concrete, a series of measures to alleviate salt erosion are proposed. The results show that the performance of asphalt concrete suffers significantly in salt environment, and the cohesion of asphalt and the adhesion of asphalt-aggregate interface are key factors in the durability of asphalt concrete. It has beneficial theoretical and practical significance for improving the durability of asphalt concrete under harsh natural environment.

The Minimal Erosive Volume Needed for Radiographic Identification of Erosions in the Metacarpophalangeal Joints in Patients With Rheumatoid Arthritis.

To compare in images, obtained by high-resolution peripheral quantitative computed tomography (HR-pQCT) and conventional radiography (CR) of the second and third metacarpophalangeal (MCP) joints, the minimal erosive cortical break needed to differentiate between pathological and physiological cortical breaks. In this single-center cross-sectional study, patients with established rheumatoid arthritis (disease duration ≥ 5 yrs) had their second and third MCP joints of the dominant hand investigated by HR-pQCT and CR. Empirical estimation was used to find the optimal cut-off value for the number of erosions and total erosive volume, which were detectable between patients with and without erosions in the second and third MCP joints according to CR. The total erosive volume in the second and third MCP joints by HR-pQCT for CR-detected erosive disease was estimated to be 56.4 mm3 (95% CI 3.5-109.3). The sensitivity and specificity at this cutpoint were 78% and 83%, respectively, with an area under the receiver-operating characteristic curve (AUC) of 0.81. The optimal cut-off value for the number of erosions by HR-pQCT was 8.5 (95% CI 5.9-11.1) for CR-detected erosive disease in the second and third MCP joints. The sensitivity and specificity at this cutpoint were 74% and 88%, respectively, with an AUC of 0.81. Erosions by HR-pQCT were larger in patients with erosive damage in the second and third MCP joints by CR. We found that CR had poor sensitivity for detecting erosive disease when the erosive volume was < 56.4 mm3 or the number of erosions was < 8.5.

On the Impact of Condensation and Liquid Water on the Radial Turbine of a Fuel Cell Turbocharger

The air-management system of a proton exchange membrane fuel cell (PEMFC) is responsible for supplying the fuel cell stack with ambient air at appropriate conditions. The compressor of the air-management system can be partly driven by utilizing the fuel cell exhaust gas in a turbine. The fuel cell exhaust is partially or fully saturated with water vapor. When the exhaust gas is expanded in the turbine, supersaturation occurs. This leads to the nucleation of droplets and their subsequent growth by condensation. This study provides an overview and understanding of the various phenomena caused by condensation and liquid water in the turbine of a PEMFC air-management system. The basis for this work is previously published numerical simulations that focused on individual aspects of the above phenomena. The present work revisits these results and puts them in context to provide a comprehensive understanding. Important phenomena are the effects of condensation on turbine performance through phase change losses, release of latent heat and thermal throttling. In addition, the released latent heat offers a power potential for downstream turbine stages. Through these effects, condensation can also impact the entire air-management system. However, condensation may occur unevenly, causing a circumferential asymmetry of the turbine outflow. Liquid water in the turbine can lead to droplet erosion, corrosion, and water-induced damage. In summary, it is essential to consider condensation and liquid water when developing turbines for PEMFC air-management systems.

Investigation of the Causes of Premature Rain Erosion Evolution in Rotor Blade-like GFRP Structures by Means of CT, XRM, and Active Thermography

Premature rain erosion damage development at the leading edges of wind turbine rotor blades impair the efficiency of the turbines and should be detected as early as possible. To investigate the causes of premature erosion damage and the erosion evolution, test specimens similar to the leading edge of a rotor blade were modified with different initial defects, such as voids in the coating system, and impacted with waterdrops in a rain erosion test facility. Using CT and XRM with AI-based evaluation as non-destructive measurement methods showed that premature erosion arises from the initial material defects because they represent a weak point in the material composite. In addition, thermographic investigations were carried out. As it shows results similar to the two lab-based methods, active thermography has a promising potential for future in-situ monitoring of rotor blade leading edges.

RENAL INVOLVEMENT IN PATIENTS WITH RHEUMATOID ARTHRITIS- A HOSPITAL-BASED OBSERVATIONAL STUDY.

Background: Rheumatoid arthritis is a chronic multisystem, immuno-inammatory disease characterized by articular and extra-articular manifestations. The disease's hallmark is synovial inammation and potential to cause cartilage damage, bone erosion, and subsequent damage to joint integrity. Rheumatoid arthritis is a systemic disease with a variety of extra-articular manifestations. The predominant well-recognized systemic manifestations include Sjogren's syndrome, pulmonary, cardiac, neurological, renal, gastrointestinal, dermal involvement, vasculitis, and Felty's syndrome. Regarding renal involvement in connective tissue disease, the focus is on systemic lupus erythematosus (SLE). The affection of kidneys in RA is more or less overlooked and mainly attributed to drugs (NSAIDs, DMARDs like gold and d-penicillamine, which are less commonly used in today's scenario. The other primary etiology of kidney involvement in RA is secondary amyloidosis, commonly associated with the long-term disease process. Vasculitis with RA is a relatively less common etiology of renal involvement in RA. Renal involvement in Rheumatoid arthritis has been well documented with a prevalence of 1-5%. Although impairment of renal function is often mild to moderate, renalrelated mortality signicantly contributes to the increased mortality of RA. The kidney is involved in RA with both glomerular and tubular damage. Renal damage in RA, however, is usually asymptomatic and is detected on laboratory investigation. It is often difcult to differentiate between damage due to disease activity and drugs used to treat RA. It is a hospita Methods: l based observational study conducted at Gauhati Medical college, Assam, for one year. All Adult (&gt; 18 years) patients fullled the 2010 American College of Rheumatology Criteria for Rheumatoid arthritis were included. Patients with diabetes mellitus congestive heart failure, urinary tract infection, long standing and uncontrolled hypertension, preexisting renal disease , overlap syndrome and pregnant patients were excluded. Detailed clinical history was taken from all included patients regarding onset and duration of disease. Disease activity was measured using disease activity score -28 -(DAS-28). Routine investigation, ESR, CRP, renal function test, ultrasonography and urine for microalbuminuria were measured in all included patients. The maximum age was Results: 68 years, the minimum was 20 years, and the mean age was 40.22 ± 11.58. The study group included 38 females and 12 males accounting for 76% and 24%, respectively. The mean disease duration was 18.6 months with a range of 3-60 months. All patients presented with polyarthritis(100%). History of morning stiffness was present in 54% of patients, while 46% had generalized weakness and constitutional symptoms. In our study, microalbuminuria was found in 15 patients (30%). Mmicroalbuminuria was seen more commonly in the age group between 41-50 years. Microalbuminuria was signicantly associated with higher ESR values. Out of 15 patients positive for microalbuminuria, 13 patients had ESR &gt;50, and 7 had ESR &gt;100 with a p-value &lt;0.001. Mean CRP was 42.45 mg/l in microalbuminuria-positive patients as compared to 16.19mg/l in microalbuminuria-negative patient. Out of 15 patients with microalbuminuria positive had evidence of erosion on x-ray, with a p-value of 0.017. Conclusion: From the present study, it can be concluded that the peak age of the disease is 31-50 years, with female preponderance. Polyarthritis is the most common presenting symptom, and most patients have an insidious onset. Constitutional symptoms like fever, malaise, and anorexia are more common among the extra-articular features. Asymptomatic renal involvement is common, and microalbuminuria is frequently seen in patients with Rheumatoid Arthritis. The presence of microalbuminuria is a sensitive indicator of increased renal vascular permeability in rheumatoid arthritis patients. Immunological methods for detecting microalbuminuria should be routinely used in all Rheumatoid Arthritis patients to detect renal involvement in its initial phase to devise the most appropriate treatment.

Shoreline Recognition Using Machine Learning Techniques

Coastal areas have emerged to be the most significant and dynamic regions worldwide. Therefore, automating shoreline recognition will aid non-profit conservation authorities to reduce public budget expenditures, relieve erosion damage, and increase the climate resilience of the natural environment. In this paper, advanced ML boosting algorithms including XGBoost, and LGBM are firstly applied into shoreline recognition with aerial images (of Lake Ontario in this study). This paper first discussed the significance and a literature review of recent progress in shoreline detection. Then, this paper adopted semantic segmentation instead of detecting shoreline directly, which enables the (Machine Learning) ML model to achieve relatively high accuracy with a small amount of data. 5 high-resolution images are used for training the model in which shorelines are detected. The work was carried out in four steps: 1) labeling the contents of shoreline images as areas of water and banks; 2) training ML algorithms; 3) using the trained algorithms to classify the image content as either water or land objects; 4) post-processing by de-noising image pixels (applying a Fourier transform algorithm) to obtain a defined shoreline. The averaged training time per image for Random Forest, XGBoost, and LGBM algorithms are 195.2 sec, 71.0 sec, and 8.6 sec, respectively. The averaged accuracy is 95.6%, 96.0%, and 94.8%, respectively; the XGBoost algorithm has slightly higher accuracy, while LGBM has a significantly shorter runtime. Cross-validation of the LGBM algorithm reduced the training time by around 23% (7.0 sec) and increased the accuracy by only 1.1% (to 95.9%).

Influence of axial clearance on solid particle erosion and efficiency of governing stage in ultra-supercritical steam turbine based on rebound effect

• Solid particle erosion (SPE) are analyzed combined with rebound effect. • Erosion degree caused by rebound is less than that caused by particle first impact. • When the axial clearance increases, erosion area extends to the front of rotor blade, but erosion degree decreases. • Influence trend of axial clearance on SPE and stage efficiency is different. Based on the steam-solid two-phase flow model combined with rebound effect, the influence of axial clearance on the solid particle erosion (SPE) characteristics and efficiency in ultra-supercritical steam turbine governing stage was analyzed. The results show that the erosion damage degree caused by rebound is less than that caused by the particle first impact. With the increase of axial clearance, the number of particles rebounding back to the trailing edge of the suction surface(SS) in nozzle decreases. When the axial clearance increases, the large size particle impact velocity and impact angle move towards the leading edge of rotor blade, and the erosion area extends to the middle and front of the pressure surface (PS), resulting in the increase of erosion area. However, the particle impact angle deviates from the serious erosion angle, and the erosion degree decreases. The axial clearance has different influence trends on SPE and stage efficiency. With the increase of axial clearance, the erosion rate density decreases continuously, about 59.2%, but the stage efficiency increases first and then decreases. So the influence of SPE and stage efficiency should be comprehensively considered for the selection of axial clearance.

Dynamic response of wind turbine blade surface material under water droplet high velocity impact

When a wind turbine blade exposure to some degree of rainfall, water droplets in the atmosphere impact the blade at high velocity will causes erosion damages of the leading edge. The damages have significant influence to the aerodynamic performance of the blade, and also the cost of power generation. In this paper, a high velocity impact dynamics model of water droplet impact on wind turbine blade is develops based on SPH-FEM coupling method, where SPH model is used to model the large deformation region of the fluid domain, and FEM method is used to model the small deformation region of the structure domain. Together with properties of gelcoat material on the blade surface, effects of varying impact velocities and angles on the impact response of the gelcoat material are analysed through numerical simulation. The results show that during a high velocity impact event of water droplet, the contact force history appears two peaks. Also contact forces and strains on the blade material decreases with decreasing droplet impact velocity and impact angle, the total contact duration of the droplet during the impact decreases with increasing droplet impact velocity and angle. The present study is expected to provide theoretical guidance for enhancing the erosive capacity of wind turbine blade gelcoat material.

Air entrainment mechanism of chute bottom aerators in high-speed chute flows

In high-head dam projects, chute aerators are commonly applied as artificial aeration devices to prevent cavitation erosion damage in high-speed spillway and tunnel flows. These specific chute air–water flows are generated by jet lower-surface aeration above the bottom cavity and jet impact aeration on the bottom floor. These air entrainment processes determine the total air flux transport downstream of the chute flow. However, the differential air fluxes caused by the two different aeration mechanisms remain unclear. Based on physical model investigations, the two air entrained processes are observed by a high-speed camera, and detailed air flux data are measured in the aerator cavity and impact areas. The effects of the jet lower-surface disintegrating and then instantaneously reattaching to the chute floor are discussed. The measured air flux data indicate that the inertial jet impact entrainment dominates with increasing the Froude number, while the air flux proportion of the jet lower-surface aeration increases with the aerator height. A general prediction model for aerator cavity entrainment is proposed, considering the effects of the Froude number and jet lower-surface aeration. The scale effects of the coupling mechanism on chute aerator air entrainment highlight that aerator cavity air entrainment primarily depends on the inertial jet impact, and the main effects of aerator design on entrainment performance are manifested in the air cavity properties.

Comprehensive Testing of Sulfate Erosion Damage of Concrete Structures and Analysis of Silane Coating Protection Effect.

In order to study the protection performance of silane coating on in-service concrete structures in a sulfate environment, we collect concrete samples in the field to simulate the concrete erosion process by accelerated erosion with wetting–drying cycles. We place the samples into protected, exposed and control groups corresponding to a corrosive environment with silane protection, corrosive environment without protection and general environment for three different service conditions. A combination of ultrasonic velocimetry, CT (Computed Tomography) scan imaging, NMR (Nuclear Magnetic Resonance) pore structure analysis, strength testing and other methods are used to analyze the strength, ultrasonic wave velocity, pore structure and other characteristics of the specimens during sulfate erosion. Based on the test results, the protective effect of silane coating on concrete structures under sulfate attack is quantitatively analyzed, and an index for judging the damage rate of specimens is proposed to quantitatively analyze the protective effect of silane coating. The research results show that the damage of the concrete structure under silane protection in a sulfate-attack environment can be reduced by more than 50%; its integrity damage index and strength damage index are easily affected by the location of local defects, which leads to a decrease in the protection efficiency of the surface silane coating.

Utilization of the Psoriasis Epidemiology Screening Tool (PEST): A Risk Stratification Strategy for Early Referral of Psoriatic Arthritis Patients to Minimize Irreversible Erosive Joint Damage.

Psoriatic arthritis (PsA) can affect a diverse range of anatomical sites and its heterogeneous presentation contributes to misdiagnosis and delayed treatment with conventional and biologic disease-modifying antirheumatic drugs (DMARDs). Up to 15% of psoriasis (PsO) patients affected by PsA remain undiagnosed. Early detection and referral to a rheumatologist are crucial to optimize care and minimize irreversible erosive joint damage. To improve the rheumatology referral process, the authors propose a risk stratification tool to identify and triage patients with possible psoriatic arthritis. With the aim of ultimately assisting in early treatment initiation, this risk stratification algorithm can be used in both dermatology and primary care clinics. It is based on the Psoriasis Epidemiology Screening Tool (PEST) combined with the ClASsification criteria for Psoriatic Arthritis (CASPAR). This article intends to provide a rationale for further prospective studies whose objective would be to validate this screening algorithm.

Experimental and numerical investigation into the effect of surface roughness on particle rebound

Erosion damage and particle deposition are crucial wear phenomena in gas turbine engines. As a result, compressor efficiency decreases, stability margin reduces, and maintenance cost increases. Hence, predicting these phenomena in an accurate manner is of paramount importance for a cost-efficient, safe, and sustainable operation. Erosion and particle deposition in the annulus are affected by particle transportation in the fluid and particle-wall interaction. The latter involves the particle impact, the potential damage of the surface and/or the particle, and the particle rebound. Particle rebounds are statistical in nature due to the target surface roughness, the variability in particle sizes, and superimposed effects caused by particle shapes as well as particle rotation and particle break-up during contact. Multiple studies investigated the statistics of particle rebound, providing empirical-based models for median and spread. However, modeling the particle-wall interaction and its data spread on a transparent physical basis allows separating the effect of target roughness from superimposed effects. The presented article pursues this objective by assessing the statistical spread of particle rebound data through multiple techniques and utilizing their interdependencies. It combines experimental, numerical, and analytical considerations. For the first time, coherent boundary conditions for the experimental, numerical and analytical setup allow the distinction of the effect of roughness from the integral effect of the superimposed phenomena. A sandblast test rig equipped with laser measurement equipment was used to measure particle rebound from flat titanium and stainless steel plates at different angles. The numerical setup is developed under OpenFOAM 6 using a RANS solver for transient simulations with compressible media in combination with one-way coupled particle flows. The numerical model includes the rebound spread model proposed by Altmeppen et al. combined with the quasi-analytical rebound model proposed by Bons et al. The statistical spread of particle rebound is investigated for roughness levels that are similar to the ones of deteriorated high-pressure compressor blades as discussed by Gilge et al. The measured surface roughness of the experimentally investigated targets is used as input parameters to the numerical framework. The rebound statistics obtained in the numerical simulation are compared to the rebound data measured in the experiment. Based on this study, conclusions are drawn about which part of the rebound spread is attributable to surface roughness and which is caused by superimposed effects. It was found that the effect of surface roughness as characterized by Altmeppen et al. contributes in the order of 46 % to the rebound spread for small impact angles. However, the share in spread due to roughness gradually decreases with increasing global impact angles to a level of 13 % for angles close to 90°. The remaining percentage of rebound spread is attributed to superimposing phenomena. In addition to the rolling and sliding of aspherical particles, further phenomena such as plastic deformation and erosion of the roughness peaks during contact and the associated dissipation of energy gain in importance for steeper impact angles. Therefore, the effect of surface roughness should not be neglected in numerical simulations of particle-laden flows. Modeling the superimposed phenomena which are observed to be dominating at high impact angles opens up a further field of research.

Erosion behavior and mechanism of the HVOF-sprayed (AlCoCrFeNi)x/(WC-10Co)1-x composite coatings at different slurry sand concentrations

In the present work, the high-velocity oxygen fuel spraying technology was used to fabricate the (AlCoCrFeNi)x/(WC-10Co)1-x [x = 100 (C1), 75 (C2), and 50 (C3) wt%] composite coatings and the 316 stainless steel was used as substrates. The main BCC phase and the minor FCC phase were primary components of the AlCoCrFeNi coating. The average hardness of the C1, C2 and C3 coatings was 646 HV0.2, 741 HV0.2, and 823 HV0.2, respectively. After being eroded for 15 h, the average hardness of the eroded coatings increased. WC enhanced the erosion performance and significantly decreased the volume loss of the coatings. The volume loss rate of the coatings decreased with the erosion process owing to both the dislocation strengthening of high-entropy alloy (HEA) and embeddedness of WC. For the AlCoCrFeNi coating, the erosion mechanism consisted of a mainly ductile failure such as cutting, plowing and removed squeeze lip, and a minorly brittle failure, in which crack and spalling of BCC phase appeared. The primary erosion destruction mechanism of WC in the composite coatings was brittle fatigue wear since crack and spalling contributed to the erosion damage of WC. The ductile removal of WC was also observed in this work, such as micro-scratch.