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In actual work, slurry erosion behavior of three different HVOF sprayed cermet coatings has been studied. The coatings were developed using the powders feedstock having WC fine structured sizes, Cr3C2-NiCr 75-25 and NiCrWSiFeB, latter conventional grain sizes. The slurry erosion testing was performed using a laboratory made pot-type slurry erosion tester, at an impact velocity of 3.61m/s and 9.33 m/s and impact angle of 30 and 90°. The mechanism of material removal in slurry erosion was studied and discussed on microstructural investigations and mechanical properties under the erosion conditions. It was observed that the WC-CoCr cermet coating with fine WC grain exhibits higher erosion resistance as compared to conventional cermet coating due to its improved properties like low porosity, high micro-hardness and fracture toughness. [ABSTRACT FROM AUTHOR]

The characteristics of commercially pure titanium (CP-Ti) in erosion and erosion–corrosion conditions have been studied. The erosion-corrosion tests were carried out using a slurry impingement rig in a 3.5% NaCl solution containing 60 g/l SiO 2 particles with average size of 250–500 μm at a jet velocity of 4 m/s under impingement angles of 20–90°. The pure erosion tests were also performed by applying a potential of −1 V versus open circuit potential. The corrosion behavior of CP-Ti alloy in both stagnant and the erosion-corrosion conditions were studied using polarization technique and the synergy values were calculated. Erosion and erosion-corrosion mechanisms were determined using scanning electron microscopy. The results showed that the maximum erosion and erosion-corrosion rates occurred at an impingement angle of 40°. The impact of particles during the erosion-corrosion increased the corrosion rate to a maximum of about 2300 times compared with the stagnant condition. The results also showed positive synergisms at all impingement angles with the rates significantly higher than the pure erosion rates. It was found that about 75–90% of the removal rate in erosion-corrosion was related to the effect of corrosion on erosion. [ABSTRACT FROM AUTHOR]

Degradation of material caused by impacts of a solid particle (erodent) suspended in a liquid is called slurry erosion and is a major problem in the hydropower and maritime industry. Slurry erosion depends on many factors, e.g. liquid and erodent velocity, size, shape, angle of impact, hardness and number of erodents, and strength of a target material. The various types of test devices have been designed to investigate an effect of mentioned parameters on material resistance. In the paper are described main types of the test apparatus showing their main advantages and disadvantages. Some results of slurry erosion resistance of few groups of materials are also presented. [ABSTRACT FROM AUTHOR]

The present study reports on the erosion properties of a novel surface engineering process combining cold spray and friction stir processing. Tungsten carbide (WC-CoCr) and aluminium oxide (Al 2 O 3 ) powders were cold spray co-deposited with AISI316 using a twin powder feed system. The deposited coatings were subsequently friction stir processed to refine and redistribute the reinforcing particles and remove the coating-to-substrate interface layer, thus generating a new metal matrix composite surface. Microstructural analysis of the SprayStirred (cold sprayed then friction stirred) specimens revealed significant particle refinement and improved particle distribution over the as-deposited coatings. The erosion performance of these SprayStirred surfaces was evaluated using a flowing slurry and demonstrated an 80% decrease in volume loss over the as-received AISI316 at 30° angle of attack. For SprayStirred WC-CoCr, microhardness measurements indicated an increase of approx. 530% over the unaltered AISI316 and 100% over the cold sprayed coating. These findings highlight the considerable increase in erosion performance of the SprayStirred specimens, and thus demonstrate the benefits of this innovative surface engineering process. This outcome is attributed to dispersion strengthening, imparted by the refined tungsten carbides. Furthermore, the SprayStirred WC-CoCr coating exhibited an 85% reduction in volume loss over an HVOF sprayed WC-CoCr coating. [ABSTRACT FROM AUTHOR]

High-Cr cast irons (HCCIs) have demonstrated excellent performance during various industrial processes involving mining, oil sand slurry handling, and manufacturing. Attempts have been made to extend concentration ranges of carbon and chromium up to a higher level, e.g., 6%C and 35%Cr or higher. However, it is not clear how the Cr content influences properties of carbide, ( F e , C r ) 7 C 3 , and the ferrous matrix, and thus the performance of HCCIs during wear processes, e.g., slurry erosion for oil sand transport. In this study, we investigated how the chromium content, in the range of 5–35%Cr, affected the performance of HCCIs with 5%C during erosion tests in slurries at two pH levels and four velocities. In particular, local mechanical properties and electron work function which is a measure of electrochemical stability were analyzed for both carbides and the ferrous matrix in the HCCIs using a micro-indenter and a multi-mode atomic force microscope. First-principles calculation was conducted to understand mechanisms responsible for the observed phenomena. [ABSTRACT FROM AUTHOR]

The corrosion-erosion behaviour and mechanisms of in-situ transformed carbon fiber reinforced alumina ceramic matrix composite (C f /Al 2 O 3 ), homemade alumina (H-Al 2 O 3 ) and commercial alumina (C-Al 2 O 3 ) were investigated by a modified MSH tester. The both in-situ C f /Al 2 O 3 and H-Al 2 O 3 were fabricated by hot-press sintering in vacuum. The corrosion-erosion experiments for the three kinds of specimens were conducted respectively in 20 vol% SiC slurry of pH 2, 7 and 12 at speed of 3.67–5.76 m/s for 120 min. The static and dynamic soaking corrosion experiments at different pH solutions were also carried out. In the static soaking corrosion experiments, the in-situ C f /Al 2 O 3 exhibited better corrosive resistance than H-Al 2 O 3 and C-Al 2 O 3 in pH 2 acid solution, but in pH 12 alkaline solution the mass loss of three materials was very slight. The corrosion mechanism in pH 2 solution is the dissolution of bonding phase between Al 2 O 3 particles. In corrosion-erosion tests, the corrosion-erosion loss rate of three materials increases with velocity. The corrosion-erosion loss rate of in-situ C f /Al 2 O 3 is less than that of C-Al 2 O 3 in pH 2 slurry, but slight higher than that of C-Al 2 O 3 in pH 7 and 12 slurries. The corrosion-erosion rate of in-situ C f /Al 2 O 3 is less than that of H-Al 2 O 3 in all tested pH slurries. Due to the bonding phase dissolution of C-Al 2 O 3 in pH 2 slurry, the bonding strength between Al 2 O 3 particles weakens, which promotes the interaction between corrosion and erosion, therefore the loss rate of C-Al 2 O 3 is higher than that of in-situ C f /Al 2 O 3 . The effects of carbon fibers on the corrosion-erosion are absorbing the impact energy by debonding and bridging toughening mechanism and inhibiting the cracks propagating, as well as the weak interaction of corrosion and erosion, which result in the better wear resistance of the in-situ C f /Al 2 O 3 at pH 2. [ABSTRACT FROM AUTHOR]

This work presents a description of abrasive water-slurry jet machining (AWSJM) to improve machining capabilities of conventional abrasive water jet machine. This work proposes a novel approach of AWSJM, where the conventional abrasive water jet machine (AWJM) is equipped with a liquid (gelatin) polymer solution injection system and a programmable control valve for controlling abrasive flow rate (AFR) and polymer solution flow rate. Parametric study of gelatin enabled AWSJM reveals the improvements in machining performance. Experimental investigations have been performed by varying concentration of the gelatin, pressure of water jet, abrasive flow rate, and abrasive size. The present work identifies the optimal range of process parameters for AWSJM, with natural gelatin as binder, with the response parameters being material removal rate, kerf width, and depth of cut. Gelatin produces a coherent, three-phase, four-content beam of higher kinetic energy in comparison with AWJ and results in increased material removal rate and depth of cut, with reduced kerf width. [ABSTRACT FROM AUTHOR]

This study forms an initial investigation into the development of SprayStir, an innovative processing technique for generating erosion resistant surface layers on a chosen substrate material. Tungsten carbide – cobalt chromium, chromium carbide – nickel chromium and aluminium oxide coatings were successfully cold spray deposited on AA5083 grade aluminium. In order to improve the deposition efficiency of the cold spray process, coatings were co-deposited with powdered AA5083 using a twin powder feed system that resulted in thick (>300 μm) composite coatings. The deposited coatings were subsequently friction stir processed to embed the particles in the substrate in order to generate a metal matrix composite (MMC) surface layer. The primary aim of this investigation was to examine the erosion performance of the SprayStirred surfaces and demonstrate the benefits of this novel process as a surface engineering technique. Volumetric analysis of the SprayStirred surfaces highlighted a drop of approx. 40% in the level of material loss when compared with the cold spray deposited coating prior to friction stir processing. Micro-hardness testing revealed that in the case of WC-CoCr reinforced coating, the hardness of the SprayStirred material exhibits an increase of approx. 540% over the unaltered substrate and 120% over the as-deposited composite coating. Microstructural examination demonstrated that the increase in the hardness of the MMC aligns with the improved dispersion of reinforcing particles throughout the aluminium matrix. [ABSTRACT FROM AUTHOR]

Over 75% of domestic electric power consumption in Colombia is supplied by hydropower. Abrasive wear is degrading turbine components such as Pelton needle valve nozzles. This problem has been studied on the components themselves (in situ). However, it was necessary reproduce the same hydro-abrasive phenomena in a controlled laboratory environment. This study describes the design and construction of a test rig capable of replicating the same wear mechanism present in Pelton needle valve nozzles at Chivor hydroelectric plant. The development of the test rig allowed to conduct empirical testing for the comparison of the plasma nitriding process versus the WC-Co-Cr coat deposited by HVOF to extend the lifetime of the nozzle. Both processes showed significant improvement in hardness and wear resistance compared to the original material specification of the needle valves. [ABSTRACT FROM AUTHOR]

WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface. [ABSTRACT FROM AUTHOR]

Since experimental erosion testing is rarely feasible in the engineering practice, the estimate of erosion is often performed by numerical simulations. Computational Fluid Dynamics (CFD) codes are often equipped with utilities for wear estimation which rely on a well-established methodology. However, besides requiring stringent assumptions, this methodology involves a number of sub-models and parameterizations which, being difficult to define a priori , are potential sources of uncertainty. The objective of this work is to investigate how the erosion estimates are affected by the different sub-models and parameters of a CFD-based wear prediction model, so that its actual predictive capacity may be established. We referred to the benchmark case of the abrasive jet impingement test which, despite being widely studied both experimentally and numerically, highlights all the issues of impact erosion modelling. A systematic activity of simulation of previous experiments revealed the key role played by some fluid-dynamics related quantities, such as the formulation of the particle equation of motion, besides the erosion model. Moreover, it allowed providing guidelines for increasing the reliability of the estimates. [ABSTRACT FROM AUTHOR]

Frequent premature failure of the ISIS spallation neutron source target prompted the investigation of previously unexplored aqueous slurry erosion response of pure tantalum (Ta) with an overarching aim to improve the service life of the target; hence, reducing the disposal of radioactive waste. Understanding such response of Ta is highly significant to many other applications such as nuclear and chemical processing. In this study, powder-metallurgically manufactured pure Ta was investigated with the help of an impinging jet aqueous slurry erosion apparatus using silicon carbide particles at a range of concentration, impact velocity, and incident angle. Results revealed a unique material removal mechanism consisting formation of extensive voids/cavities all over the eroded surface. These mechanisms are discussed considering the theories of solid particle erosion and the grain boundary sliding behaviour of Ta under localised indentation loading. • Unreported aqueous slurry erosion response of PM manufactured pure Tantalum. • Surface removal mechanisms consisted of plastic deformation and micro-cutting. • Unique mechanism also included the formation of extensive voids/cavities. • Results explained using grain boundary sliding behaviour under indentation loading. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) have gained extensive attention due to their excellent properties and the related scientific value in the last decade. In this work, AlxCoCrFeNiTi0.5 HEA coatings (x: molar ratio, x = 1.0, 1.5, 2.0, and 2.5) were fabricated on Q345 steel substrate by laser-cladding process to develop a practical protection technology for fluid machines. The effect of Al content on their phase evolution, microstructure, and slurry erosion performance of the HEA coatings was studied. The AlxCoCrFeNiTi0.5 HEA coatings are composed of simple face-centered cubic (FCC), body-centered cubic (BCC) and their mixture phase. Slurry erosion tests were conducted on the HEA coatings with a constant velocity of 10.08 m/s and 16–40 meshs and particles at impingement angles of 15, 30, 45, 60 and 90 degrees. The effect of three parameters, namely impingement angle, sand concentration and erosion time, on the slurry erosion behavior of AlxCoCrFeNiTi0.5 HEA coatings was investigated. Experimental results show AlCoCrFeNiTi0.5 HEA coating follows a ductile erosion mode and a mixed mode (neither ductile nor brittle) for Al1.5CoCrFeNiTi0.5 HEA coating, while Al2.0CoCrFeNiTi0.5 and Al2.5CoCrFeNiTi0.5 HEA coatings mainly exhibit brittle erosion mode. AlCoCrFeNiTi0.5 HEA coating has good erosion resistance at all investigated impingement angles due to its high hardness, good plasticity, and low stacking fault energy (SFE).

The current experimental work is focused on development and characterization of HVOF sprayed VC-TiC+CuNi-Cr based coatings on hydro-machinery steel SS316. Empirical correlations for mass loss have been developed with the aid of response surface methodology (RSM) approach. Central composite design (CCD) matrix has been acquired with five different levels over four impingement parameters namely impingement angle, jet velocity, slurry concentration, and exposure time. When compared with bare SS316 steel, a significant increase in the slurry wear resistance of SS316 steel was noticed for different variants of developed coating. Moreover, ductile erosion mode was observed in coatings containing CuNi-Cr as the main component, which was reported to transform into the brittle mode with increasing VC-TiC percentage. [ABSTRACT FROM AUTHOR]

The high-speed flow of sand-carrying fracturing fluid through tee junctions causes severe erosion and affects the safety of the fracturing operation. This study improves the traditional computational fluid dynamics-discrete element method (CFD-DEM) to avoid the (dense particles) collision-leading abnormal penetration but also considers the influence of fracturing fluid viscosity on particle collisions. Then the tee junction erosion model under fracturing conditions is established and verified by experiments. The simulation analysis shows that with the increase of two-phase flow velocity and Stokes number, the dominant effect of particle motion and collision changes from viscous force to inertial force, and then the tee junction erosion position also changes. [ABSTRACT FROM AUTHOR]

The impingement angle has a significant influence on the slurry erosion behavior. There is limited knowledge of the effect of the impingement angle on the erosion of the micro-structured surface. Slurry erosion experiments were carried out on the V-shape grooved surface at four different impingement angles (30°, 45°, 60°, and 90°) in the slurry with 5.1 m s−1 velocity and 5 wt% sand content. Mass loss measurement, surface micro-morphology, roughness test, and nanoindentation revealed the relationship between microstructure damage and impingement angle. The effects of the area and impingement angle on erosion were discussed. The results show that the slurry erosion of the V-shape grooved surface displays a similar trend with the impingement angle to the smooth surface but with a relatively low erosion degree. The slurry erosion is alleviated to the most at the impingement angle of 45°. The ratio of the top surface to the grooved surface and the actual impingement angle to the grooved surface play essential roles in reducing the slurry erosions. This work can help to design the surface microstructure and set the relative position of the impingent flow to the target material surface. [Display omitted] • Grooved samples still follow the same trend with angle as ductile materials. • The most severe erosion and the maximum erosion reduction both locate at 45°. • The top surface contributes more erosion than the grooved surface to the damage. [ABSTRACT FROM AUTHOR]

In this research work, different compositions of VC (Vanadium Carbide) +CuNi-Cr (Cupronickel-Chromium) ranging from 0% to 100% were deposited over hydro-machinery steel (SS316) with the help of HVOF spraying system. The slurry erosion for different composition of coatings and bare SS316 steel have been evaluated with the help of slurry erosion testing machine. From the experiments, it was concluded that amongst all the developed coatings, 100% VC based coating has shown exceptionally good resistance to slurry erosion as compared to other composition of coatings owing to extra microhardness attained by VC granules. Brittle mode of erosion mode was observed for coating with VC as major constituent, which was reported to be converted to ductile mode with the increase in CuNi-Cr addition percentage. [ABSTRACT FROM AUTHOR]

Slurries conveyed in conduits generate erosion caused by particle impacts on the walls. Those impacts result from the average velocity and the turbulence of the carrying liquid. We investigate the erosion and relevant flow features, when the dilute slurry passes from the inner to the outer annulus through four equally spaced rectangular apertures on the periphery of the tube dividing these two conduits. The flow of dilute slurry was solved numerically. A consideration was given to the effects of particle size on erosion rate and statistical distribution of impact velocity, angle, and total erodent mass inducing wear. In addition, the numerical solution of the continuous phase velocity was validated with measurements. A confined trailing vortex forms at the longitudinal edge of the aperture, amplifying the erosive wear on the outer wall of the annulus. A large amount of particles passes near the aperture׳s horizontal downstream edge and intensifies the erosion rate above it. The effect of these flow features becomes more pronounced for larger particles. The statistical analysis of impact velocity, angle, and mass showed that the mean velocity in the channel dominates erosion caused by impacts of large particles. On the other hand, the near-wall turbulence mainly affects the erosion resulting from impacts by small particles. [ABSTRACT FROM AUTHOR]

The present work reports on the examination of three High Velocity Oxy Fuel deposited coatings, Tungsten Carbide, Chromium Carbide and Aluminium Oxide, under slurry erosion and dry erosion conditions. The density and hardness of coatings produced in this manner are typically superior to other thermal spray processes, and are therefore suitable for use in corrosive and highly erosive environments. The primary aim of this investigation was to establish the total mass and volume loss from each coating under dry and slurry erosion testing conditions and compare the level of material loss following the respective testing regimes. The scope of the study incorporated the application of cathodic protection to prohibit the effects of corrosion in the case of slurry erosion testing. This approach ensured that any damage to the surface could be attributed to pure erosion, and as such, be assessed against the dry erosion test data. Subsequent examination of the resulting wear scars facilitated assessment of the level of damage caused by the impinging slurry. Results revealed variation in the level of degradation experienced by each coating type under the respective test conditions. Under both dry erosion and slurry erosion, Tungsten Carbide with a Cobalt binder proved an effective protective coating by exhibiting a reduction in material loss over other assessed coatings. [ABSTRACT FROM AUTHOR]

The present study examines three High Velocity Oxy Fuel deposited coatings, Tungsten Carbide, Chromium Carbide and Aluminium Oxide, under slurry erosion-corrosion conditions. Coatings produced in this manner typically exhibit superior density and hardness over alternative thermal spray technologies, therefore are suitable for use in corrosive and highly erosive environments. The scope of the study concentrates on isolation of the contributing factors of erosion, corrosion and synergy through applied electrochemistry, as well as metallographic analysis to evaluate the mechanisms causing coating degradation. The aim of which is to provide comprehensive data on the performance of the mentioned coatings under erosion-corrosion in conditions representing a flowing environment. Results demonstrate the breakdown of Chromium Carbide and Aluminium Oxide coatings result in enhanced mass loss over the uncoated S355 steel. Despite this, results have shown Tungsten Carbide with a Cobalt binder to be an effective protective coating, resulting in a significant reduction in total material loss over uncoated S355 steel. [ABSTRACT FROM AUTHOR]

Slurry erosion wear performance of glass fibre reinforced vinylester composite (FRP) has been studied using a pilot-scale erosion test apparatus. Tests were conducted at elevated temperatures in aqueous and acidic environments. When using fine quartz as an abrasive material, FRP showed higher mass losses in the aqueous environment than in the acidic conditions, especially at higher temperatures. In this case, the FRP degradation was governed by the penetration of the used medium into the FRP structure. According to the absorption studies, the weight gain of the laminate was more pronounced in the water immersion compared to the acidic solution, which can be a prediction of an increased degradation rate and explain the higher wear in the aqueous medium. When the abrasive material was changed from fine to coarse quartz, the removal of the shielding matrix phase was extensive and a direct route for the acidic solution to the fibres was created causing more severe damage. This was also shown in scanning electron microscopy (SEM) studies, where the samples tested in the acidic solution showed extensive fibre flattening along the erosion flux. By increasing the test temperature close to the boiling point of the medium, an increase in the FRP wear could be seen. The increase in the rotation speed, on the other hand, did not automatically mean higher mass losses. This shows that the wear environment in the present test device is highly complicated with several interrelated parameters affecting the results. [ABSTRACT FROM AUTHOR]

Three commercially available quenched wear resistant steel grades were compared with a structural steel and four elastomer materials to reveal the differences in their behavior in slurry erosion conditions and to find the best solutions for demanding applications. A slurry-pot tester, allowing simulation of various wear conditions with different minerals, particle sizes (up to 10 mm), abrasive concentrations, and sample angles were used to simulate different industrial slurry applications. In this study, granite and quartz with concentrations of 9 and 33 wt% were used as abrasives in tests conducted at 45° and 90° sample angles. The performance of the studied steels was evaluated with respect to their material properties such as hardness and microstructure. Furthermore, the cross-sections and wear surfaces of the test samples were analyzed to reveal the possible differences in the mechanical behavior of the materials during slurry erosion. The wear surface analyses show that abrasion is the dominating wear mechanism already for the smallest particle size of 0.1/0.6 mm. In low-stress abrasive slurry erosion with the smallest particles, the elastomers showed better wear resistance than the steels, whereas in demanding high-stress abrasive slurry erosion conditions the quenched wear resistant steels can well compete with elastomers in wear resistance. The relative wear performance of the steels increased with increasing abrasive size, while for the elastomers it decreased. [ABSTRACT FROM AUTHOR]

Cemented tungsten carbide systems have been widely used in machine tools, ammunition rounds, and sporting equipment, as they possess the necessary combination of hardness and toughness to endure wear environments. In most applications, the abrasion phenomena has been identified as one of the sources of surface damage and material degradation. In this work, WC–Ni hardmetal is doped with zirconium carbide or titanium carbide to improve its abrasive and erosive wear resistance. TiC has been known to produce platelet grain structure meant for strengthening leading to enhanced abrasion resistance. ZrC can suppress grain coarsening and abnormal growth of WC grains while increasing hardness. Tribological characteristics are obtained from slurry and dry erosion, as well as high and low stress abrasion tests. The composite of WC–8Ni–TiC works best overall for various wear conditions with exception of high stress abrasion. WC–8Ni–ZrC does not provide any benefit of wear resistance in this study. Wear rate and mechanisms of wear were analysed by and discussed based on scanning electron microscopy studies. [ABSTRACT FROM AUTHOR]

Solid particle shape and size effects on the slurry erosion behavior of AISI 5117 carbon steels are investigated, using whirling-arm ring for two different erodent particles, namely, silica sand (SiO2) and silicon carbide (SiC). From this work, it was found that aspect ratio and circularity factor (CF) increase for silica sand and decrease for silicon carbide with increasing size. The erosion rate increased with the increase of particle size for the two types of erodent particles and its value was greater in the case of silicon carbide particles. At the same test conditions, it has been noticed that the particle size plays the major role in the slurry erosion of 5117 steels in comparison with the aspect ratio and circularity factor. Microcutting and plowing with serrated wear tracks were observed for coarse SiC particles having irregular and angular shape. But, for coarse SiO2 particles which had a rounded shape, the main mechanism was plowing with plain and smooth wear tracks for an impact angle of 30 deg. Indentations and material extrusion prevailed for the coarse size of the two erodents for an impact angle of 90 deg. [ABSTRACT FROM AUTHOR]

Slurry erosion resistance of 13Cr4Ni stainless steel is studied after thermo-mechanical processing. Thermo-mechanical processing was performed using thermo-mechanical simulator Gleeble® 3800. Deformation strain rates of 0.001 and 10 s −1 were used at 950 °C and 1050 °C. Refined prior austenite grain size and lath packets of martensite obtained after thermo-mechanical processing were studied using optical micrographs. The thermo-mechanically processed specimens showed higher slurry erosion resistance as compared to the as-received stainless steel. Specimen thermo-mechanically processed at 950 °C using a strain rate of 0.001 s −1 showed the best resistance to slurry erosion. The mechanism of erosion is discussed by correlating with microstructure and mechanical properties. Refined prior austenite grain size and martensite lath packets resulting from the thermo-mechanical processing are responsible for the enhanced slurry erosion resistance of the processed specimens. [ABSTRACT FROM AUTHOR]

Fluidic oscillator made of tungsten carbide, the core component of the fluidic hammer, has a significantly reduced service life under the erosion wear of drilling fluids with solid particles. Polycrystalline diamond composite (PDC) has the potential to solve this issue due to its extremely high hardness and wear resistance benefits. However, few studies on the slurry erosion wear of PDC have been reported. In this paper, a modified slurry erosion experimental device based on submerged abrasive water jets was used to study the erosion resistance of four grades of PDCs with grain sizes of 2–3, 5, 10 and 25 μm respectively. The erosion surface of the damaged PDC was observed by scanning electron microscope (SEM) and the erosive mechanism of the PDC was analyzed. The experimental results showed that PDC had excellent slurry erosion resistance. The erosion rate of PDC was 1/192–1/43 of that of tungsten carbide when the jet velocity was 100 m/s. The erosion rates of PDC increased with the rise of jet velocity, impact angle and erodent particle size. In addition, the erosion performance of debris represented by quartz to PDC is greater than that of weighting agents represented by barite and hematite. Further research also showed that PDC with fine grain has greater erosion resistance than PDC with coarse grain, except PDC2 ~ 3. At a high impact angle, the erosive mechanism was forming the craters due to the crushing of diamond grains and the pits due to the overall pullout of diamond grains, while at a low impact angle, the erosive mechanism was ploughing and forming directional craters. • A modified slurry erosion experimental device was developed. • Diamond grain size has a significant effect on the erosion rate of PDC. • The erosion rate of PDC is affected by fluid parameters and erosion particle properties. • The erosive mechanisms of PDCs were analyzed. [ABSTRACT FROM AUTHOR]

The effect of microstructure and mechanical properties on the slurry erosion behavior of carbide-free bainitic (CFB) steel, austempered at 350, 400 and 450 °C and quenched and tempered martensitic (QT) steel, tempered at 300, 400 and 500 °C has been investigated using slurry pot tester and silica sand erodent particles. The samples were tested for 15 h with a rotating speed of 1000 rpm. The result shows that the QT steel has better erosion resistance than the CFB steel. The retained austenite (RA) phase fraction (17.75%) in 350 °C austempered sample, which provides erosion resistance by transformation-induced plasticity effect, is sufficient for outstanding erosion performance among the CFB steels. However, this RA phase fraction in CFB steel is inadequate to provide better erosion resistance than the QT steel. Among all the samples tested, the sample which is tempered at 300 °C shows the best slurry erosion resistance. The analysis of the results suggests that the hardness and transformation-induced plasticity associated with RA phase fraction, are the deciding factors for erosion resistance in QT and CFB steel, respectively. The material removal mechanism in the CFB steel is the crater formation leading to fatigue failure of lips and coalescence of micro-craters, whereas in QT steel it is only fatigue failure of lips. • The slurry erosion of carbide-free bainitic and martensitic steel has been studied. • The martensitic steel reveals superior erosion resistance due to higher hardness. • Retained austenite is inadequate to provide better erosion resistance in bainitic steel. • Formation of craters and lips and coalescence of micro-craters are revealed. [ABSTRACT FROM AUTHOR]

The slurry particle concentration effect on the erosion rate of tool components is a critical factor in the design and maintenance of industrial equipment. The relationship between slurry particle concentration and erosion rate was tested and evaluated at a jet impingement test facility using glass spheres impacting acrylonitrile butadiene styrene (ABS) coupons. Particle concentration ranged from 4.6% to 22.4% by weight, and three different nozzle standoff heights were used ( H / D =3.0, 5.2, and 7.4). The results show the erosion rate is dependent on the slurry concentration and the test duration. Two distinct erosion profiles correlated with changes in erosion rate over the test duration. The transition between the erosion profiles and the change in erosion rate were dependent on the initial test geometry and slurry concentration. [ABSTRACT FROM AUTHOR]

In this study, high-velocity oxygen-fuel sprayed amorphous coatings have been heat treated at various temperatures to form microstructures with crystalline phases. The structure, micro-hardness, cavitation erosion resistance and erosion–corrosion resistance of these coatings are compared. Crystalline phases are discovered in the coatings after heat treatments at 650 °C and 750 °C. The coating heat treated at 750 °C exhibits the poorest cavitation erosion resistance in 3.5 wt% NaCl solution among all coatings due to the degraded corrosion resistance. However, the hardness of the crystallized coating can reach 1000 Hv and the erosion–corrosion resistance of the heat treated coating is better than the untreated one. [ABSTRACT FROM AUTHOR]

SiC foam/epoxy co-continuous phase composites (SiC foam /EPs) that were composed of the E-51 epoxy (EP) matrix and the SiC ceramic foam (SiC foam ) reinforcement were prepared as the erosion resistant materials. The erosive behaviors of SiC foam /EPs were investigated by using a rotating disk rig. The effects of sand content ( C ), flow velocity ( V ), test duration and SiC volume fraction on the erosive behaviors of SiC foam /EPs were studied through the mass loss test, SEM and CLSM (Confocal Laser Scanning Microscope) observations. Under different experimental conditions, the erosion rate ( E r , defined as the ratio of erosion ( E c ) and time) was relatively larger before the transition point, but E r clearly decreased after the transition point. E c of SiC foam /EPs increased with flow velocity ( E c ∝ V 3 ) and sand content ( E c ∝ C ). The erosion angle ( α , the angle between the eroded and initial surfaces) of SiC foam /EPs increased linearly with flow velocity and sand content. Under the test conditions, flow velocity was the dominant factor for the erosive behaviors of SiC foam /EPs. E c and α of SiC foam /EPs both decreased with the increase of SiC volume fraction. The erosion of SiC foam /EPs obeyed the linear rule of mixtures (LROM) averaging law since EP and SiC foam were eroded by a parallel process. [ABSTRACT FROM AUTHOR]

The erosion performance of laser cladded Ni-60 %WC coatings subjected to a controllable abrasive water jet (AWJ) was investigated. The erosion resistance of Ni-60 %WC coatings at varied linear laser energy (from 315 to 700 J/mm) was examined under different impinging angles of a slurry jet. The chemical composition of coatings was modified by nanocrystalline WC powder and the rare earth element (LaO). The erosion value of Ni-60 %WC was reduced to 40 % by decreasing the laser energy from 700 to 315 J/mm. Synthesized coatings with optimal weight fraction of nano-WC particles (5 %) and LaO (1 %) decreased the average microstructural grain size of the Ni-binder, increased the homogeneity and hardness of the coating, and consequently increased the erosion resistivity. The tribological evaluation of the erosion scars showed a log-linear relationship between coating hardness and volume loss under erosion. Adding nano-WC (5 %) and LaO (1 %) enhanced the bonding strength between Ni and WC and no pulled out WC particles was observed after erosion test. [ABSTRACT FROM AUTHOR]

More and more slurry transport systems are used in mining operations to efficiently and cost-effectively transport ores and tailings. The materials used for slurry transport are often subjected to severe wear attack. In this study, the wear modes and wear resistance of materials commonly used for slurry transport are discussed. Slurry jet erosion, Coriolis slurry scouring erosion and slurry sliding abrasion tests are used to simulate these wear modes and to characterize the wear resistance of the materials. The wear resistance of selected materials from each material category commonly used for slurry transport, including steels, high chromium white cast irons, chrome carbide-based and tungsten carbide-based overlays, elastomers, plastics, ceramics and cermets, are reported. The relationships of the wear resistance of these materials with their mechanical properties are also briefly discussed. [ABSTRACT FROM AUTHOR]

Slurry erosion and cavitation erosion tribometers are used to evaluate wear on materials of hydromachinery components, in this work numerical simulations based on computational fluid dynamics (CFD) were implemented with the aim to analyze the influence of parameters such as shape and size of cavitation inducers, rotational speed, particle concentration and cavitation inducer-specimen separation over the mass loss rate. Operating parameters were determined, which are suitable to reproduce typical cavitation erosion and slurry erosion conditions presented in turbomachinery devices like Francis turbine runners under off-design conditions or exposed to a high amount of sediments. CFD analysis provides a numerical insight about the flow field and its behavior due to the influence of shape and location of the cavitation inducers aiming to predict the zone where the cavitation process takes place. Also, it was found that CFD simulation coupled with particle tracking methods provide an understanding about the interaction between the hard particles and the surfaces tested, and its influence over erosion rates. [ABSTRACT FROM AUTHOR]

Slurry erosion is a complex process with number of interacting variables (operating and material parameters). We study the interaction between erodent concentration and impingement angle using experimental and computational fluid dynamics (CFD) techniques. Experiments were performed using a high velocity slurry erosion test rig at a constant velocity with dilute slurries of water and sand particles. Concentration of sand in water was varied from 0.01 wt% (100 ppm) to 0.5 wt% (5000 ppm) at three sample orientations (30°, 60° and 90°). Six different targets, three bulk materials (aluminum, cast iron, and stainless steel) and three thermal sprayed coatings (Ni+20, 40, and 60 wt% of Al 2 O 3 ) were used for slurry erosion tests. Experimental results showed a significant interaction between erodent concentration and impingement angle. The concentration variation showed larger influence on erosion rate for sample held normal to the slurry jet compared to glancing angle. The degree of interaction was different for different materials. CFD simulations showed higher particle-to-particle interactions for sample at glancing angle compared to that at normal angle. This probably explains the low contribution of concentration variation at glancing angle compared to the normal angle. Further, the effect of concentration on erosion rates was also influenced by the restitution coefficient (function of material and impact parameters). For a high restitution coefficient materials, the change in slurry concentration showed minimum effect on erosion rate compared with low restitution coefficient materials. [ABSTRACT FROM AUTHOR]

The prediction of erosion damage caused by solid particles within flow lines is crucial for many industries. In most erosion modeling approaches, empirical erosion equations are commonly used to relate particle impact information to erosion magnitude. These equations are usually generated from jet impingement testing in air, since the particle impact speed and angle are assumed not to deviate from conditions in the jet. However, in slurry flows, a wide range of particle impact angles and speeds are produced on the target surface. In this work combining CFD simulation results with experimental data obtained from a normal slurry jet test, an erosion equation has been developed. In this methodology, a computational fluid dynamics (CFD) simulation is used to characterize the particle impact speed, angle and frequency at specific locations on the specimen. Then, the particle impact data are related to the measured erosion depth to achieve an erosion equation from submerged testing. The erosion equation has been validated for oblique impingement configurations and it has been shown that, the equation is well suited for various test conditions and it can successfully predict the local erosion depth. Furthermore, a series of dry impinging jet tests for normal and oblique configurations has been performed. Utilizing a particle image velocimetry (PIV) technique, the slip velocity between the gas and sand particles has been determined. In order to gain a better understanding of the erosion pattern, local erosion depth has been measured using a 3D surface profilometer. The effect of gas velocity and impingement angle on erosion profile has also been investigated. [ABSTRACT FROM AUTHOR]

In the paper, the contributions of corrosion, erosion and synergy to the erosion–corrosion degradation of Ti(C,N)–based cermets are investigated in the different slurry conditions, and respect to the synergistic effect, corrosion enhanced erosion and erosion enhanced corrosion are also quantified. The results indicate that the contributions of corrosion, erosion and synergy to the erosion–corrosion degradation of Ti(C,N)–Ni cermets are strongly environment dependent. With increasing the environmental corrosivity, the contributions of corrosion and synergy are enhanced, and the erosion role in erosion–corrosion is strengthened significantly with the increased erosion severity. With the increased time, the erosion role is increased and the corrosion role is decreased in the erosion–corrosion conditions. Corrosion enhanced erosion and erosion enhanced corrosion have both increased with the increased time, however the increment of corrosion enhanced erosion is much more than that of erosion enhanced corrosion. Corrosion enhanced erosion is more significant than erosion enhanced corrosion, and corrosion enhanced erosion plays a dominant role in the synergy. [ABSTRACT FROM AUTHOR]

The current study investigates a ceramic, two sintered cermets and a metal under solid–liquid impingement with 3.5% NaCl and 150 mg/l silica sand at two extreme angles of attack, 90° and 20°. The materials tested were zirconia ceramic, sintered WC–6Co, sintered WC–6Ni and UNS S31600. Each material was exposed to a testing regime using re-circulating impinging jet apparatus with a velocity of 19 m/s over a test duration of 1 h. The electrochemical properties of the materials were investigated in-situ through anodic and cathodic polarisations and application of cathodic protection (CP). Post experimental analysis of the degraded surface was completed using Scanning Electron Microscopy (SEM) and Optical 3D Imaging. At 90° angle of impingement, zirconia exhibited a brittle response to erosion–corrosion testing with the mass loss being fifty times greater than the negligible mass loss at 20° angle of impingement. WC–6Co and WC–6Ni both outperformed UNS S31600 under all solid–liquid impingement erosion–corrosion testing regimes. WC–6Ni exhibited slightly better erosion–corrosion resistance over WC–6Co at both 90° and 20°. UNS S31600 displayed the best corrosion resistance but its passive film was continuously damaged due to the presence of solid into the liquid solution. The nickel binder increased the corrosion resistance of WC–6Ni over WC–6Co. Cathodic protection was successfully applied on sintered WC–6Co and UNS S31600 isolating the key components of erosion–corrosion. [ABSTRACT FROM AUTHOR]