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Slurry erosion can cause severe damage and often constitutes a significant portion of the total production cost in many industries such as oil sands and mining. The most commonly used materials for such applications are metallic materials having a composite microstructure consisting of hard reinforcement phases in a more ductile metal matrix. Typical examples are high chromium white irons and tungsten carbide welding overlays. The main purpose of this work is to evaluate the scouring erosion resistance of such materials for applications in handling fine sand slurries and to introduce a wear model to help understand the correlation between erosion resistance and the characteristics of microstructures. Five high chromium white cast irons and four spray and fusion coatings composed of cast tungsten carbide particles and Ni–Cr–B–Si–Fe matrix have been studied using a Coriolis scouring erosion tester in a fine sand slurry. The relationship between the erosion resistance and different microstructure parameters was explored. For the chromium white cast irons, the erosion resistance increased with increase in carbide volume fraction but the spray and fusion coatings showed the opposite trend, i.e., their erosion resistance decreased with increase in the carbide volume fraction. No clear correlation was found between erosion resistance and free path for the spray and fusion coatings while for the chromium white cast irons, the erosion resistance was found to increase rather than decrease with increase in free path. To help explain the experimental results, a wear model has been proposed for the wear resistance of composite microstructures composed of a reinforcement phase (RP) and a metal matrix. In the model, the wear surface of the material is distinguished by four different features/regions, each having unique wear resistance. The rule of mixtures (ROM) for wear resistance is applied to formulate the wear resistance of the material with the above four wear surface features. It is shown that the results can be reasonably well explained based on the proposed model by using the total edge length, L , of the RP particles exposed on a unit area of the wear surface. • Find sand slurry scouring erosion of Cr white irons and WC coatings studied. • A rule of mixtures wear resistance model is proposed. • Wear surface is assumed to consist of four regions with distinctive wear resistance. • Carbide edge effect and shadow protective effect are considered. • Carbide edge length was found to be important parameter affecting wear resistance. [ABSTRACT FROM AUTHOR]

The present study compares slurry erosion resistance of austempered and tempered medium carbon high silicon steels. A 0.62C-1.91Si-0.85Mn-0.23Cr steel was subjected to austempering at 300, 350 and 400 °C for 10 min to develop a microstructure comprising of bainite and retained austenite. With the increase in the austempering temperature, the mechanical stability of retained austenite decreased, and the size of bainitic ferrite laths increased. As a result, strain hardening ability and toughness of the steels decreased with austempering temperature. Another set of steel with the same composition was quenched and tempered at 300, 450 and 550 °C for 60 min. An increase in the tempering temperature led to an increase in the size and fraction of carbides and a decrease in the mean free path and dislocation density. Strain hardening ability and toughness of tempered steels was substantially small than austempered steels. Both the austempered and tempered steels were subjected to slurry erosion. Austempered steels exhibited higher slurry erosion resistance as compared to tempered steels. Slurry erosion resistance of austempered steels has been noted to depend on the mechanical stability of retained austenite and the size of bainitic ferrite laths. Due to the difference in the extent of deformation-induced transformation of retained austenite into martensite in the steels austempered at different temperatures, number of mobile dislocations generated (to accommodate the dilatation due to transformation) in bainitic ferrite laths differed. A large number of mobile dislocations in the specimens austempered at 300 °C blunted the propagating crack and delayed the material loss during erosion. The erosion resistance of tempered steels was observed to decrease with an increase in tempering temperature. A large fraction of coarse carbides led to the formation of many decohesion sites in steels tempered at 450 and 550 °C. Further, a small number of mobile dislocations present per unit volume in the steels tempered at high temperatures could not resist the propagation of cracks nucleated from the decohesion sites leading to a high erosion rate in these steels. • Austempered microstructure exhibit better slurry erosion resistance as compared to the tempered microstructure. • Steel containing fine carbide free bainite along with blocky retained austenite exhibit higher slurry erosion resistance. • Erosion resistance of tempered steels with large size and fraction of carbides and small dislocation density is small. [ABSTRACT FROM AUTHOR]

A simple method is proposed to describe solid particle erosion in a bend. The key to the new model is to solve the flow field and particle trajectory in the bend. The present model works based on two mechanisms. First, the axial velocity of the fluid entering the bend satisfies the conservation of angular momentum. Second, the solid particle follows a curved trajectory in a plane parallel to the symmetry plane of the bend due to the drag force of the fluid. When the drag force of the fluid on the particles is sufficiently strong, an explicit solution of the particle trajectory can be obtained. The solid particle erosion in the bend can be solved by substituting the impact parameters into particulate erosion theory. Each step of the new model is verified by comparing the predictions of the axial velocity profile of the fluid, the axial velocity profile of the particle, and the solid particle erosion on the outside of the bend with experimental data available in the literature. Furthermore, the applicability of the present model is also discussed in detail. • An approximate theoretical solution of solid particle erosion in a bend is obtained. • Each step of the new model is verified by comparing with experimental data. • An explicit solution for the particle movement in a bend is derived when S t ≤1. • The particle trajectory in a bend is proven to be an Archimedean curve when S t <1. [ABSTRACT FROM AUTHOR]

Cobalt-based and nickel-based coatings were successfully produced using TIG welding and laser cladding technologies as alternative materials with higher cavitation erosion (CE) and slurry erosion (SE) resistance, respectively. Their structure, phase constitution, hardness and elastoplasticity were characterized. Combined with the cumulative mass loss, erosion morphology and roughness, the CE and SE resistances were compared and erosion models were also proposed. The results show that the cobalt-based coating exhibited much better CE resistance and lower SE resistance than the nickel-based coating. The phase transition contributes mostly to the high CE resistance of the cobalt-based coating. While, the combined effects of high hardness, elastoplasticity and hard phases' anchoring and shielding, determine the high SE resistance of the nickel-based coating. • TIG welding Co- and laser cladding Ni-based coatings were performed respectively. • Ni-based coating has higher hardness and elastoplasticity than the Co-coating. • Co-based coating has higher cavitation erosion but lower slurry erosion resistance. • Phase transition effectively resists the cavitation erosion of Co-based coating. • Anchoring of the hard phases favors the high SE resistance of Nickel-based coating. [ABSTRACT FROM AUTHOR]

A series of commercial and non-conventional heat treatments was performed to modify the initial as-cast microstructure of two high-chromium (14 wt% and 18 wt% Cr) white cast irons and a low chromium nickel-bearing grade (Ni-Hard 2) for slurry pumping applications. The effect of each heat treatment on the microstructure of the alloys was carefully investigated by optical and scanning electron microscope and X-ray diffraction analysis. Samples were tested for impact erosion resistance in flowing slurry by using a modified-Coriolis apparatus and their weight losses were related to microstructure and hardness. The analysis showed that the erosion resistance of these alloys is related to the carbides volume fraction and hardness, in combination with the matrix microstructure. In case of high-chromium white irons, the destabilization heat treatment (950°C-2h) produced a hard martensitic matrix with secondary carbides that gave superior erosion resistance compared to all other conditions. Excellent performances were obtained also for Ni-Hard 2 in as-cast condition, indicating that this alloy could be an economic alternative to high chromium irons in applications where good erosion resistance is required. • Erosion resistance of WCIs depends on carbides percentage and matrix microstructure. • Destabilized high-Cr alloys have the highest erosion resistance. • Excellent behaviour of Ni-Hard 2 is related to large amount of ledeburitic carbides. • Austenitic matrix of high-Cr alloys treated at 1160 °C gives good erosion properties. [ABSTRACT FROM AUTHOR]

The API Spec 6AV1 standard specifies the design requirements for valves operating in fields with sand production in order to reduce the risk of failure. In one of the validation tests, a valve is cyclically opened and closed under controlled conditions whilst a sand slurry is flowing in the loop. The carrier fluid is water with polymer viscosifiers to increase the viscosity up to about 55 cP. After completion of around 500 opening-closing cycles, high static pressure is applied upstream the valve to check for possible leakage. Objective of this study was to assess whether the occurrence of leakage might be affected by testing parameters that, being not specified by the standard, are decided by the experimenter; among them, particular attention was paid to the pressure and flow conditions during the valve operation. To this aim, numerical simulations were carried out combining different modelling approaches, and analyzing the failure of the valve from the point of view of the damage produced by impact wear. The difficulties inherent in the task of estimating erosion via numerical simulations are further enhanced in this work, since a number of complex case-specific issues had to be faced. First, the movement of the valve stem. Second, the co-existence of laminar and turbulent flow conditions due to the high viscosity of the carrier fluid. Third, the simulation of the valve as part of the entire loop. Fourth, the identification of a suitable indicator of valve leakage. Apart from the interest from a modelling point of view, the obtained results can help to improve the specification test procedures and acceptance criteria in the future. • The test procedures of the API 6A standard for safety valves are discussed. • The risk of valve leakage is related with the erosion severity. • The execution of the test in a real flow loop is numerically simulated. • Multiple computational approaches are integrated. • Significant influence is exerted by testing parameters unspecified by the standard. [ABSTRACT FROM AUTHOR]

Elastomers and plastics are widely used as the materials for handling abrasive/erosive slurries because of their wear resistance, toughness, corrosion resistance and light weight. In this study, slurry jet erosion, Coriolis slurry scouring erosion and large particle slurry erosion are used to characterize the erosion resistance of selected elastomers and plastics, including two natural rubbers, a neoprene rubber, a polyurethane and three types of polyethylene, at different test conditions. The wear rates and wear modes of the tested materials are presented and the relationships between the erosion resistance of these materials and their mechanical properties are discussed. Suitable applications of these materials in slurry transport are also recommended. • Elastomers have excellent erosion resistance because of their excellent resilience to absorb deformation elastically. • Plastics have good erosion resistance because of their moderate resilience to absorb deformation elastically. • Elastomers and plastics are suitable for resisting erosion attacks by small and rounded or semi-rounded particles. • Elastomers and plastics have displayed increased erosion resistance at elevated temperature. [ABSTRACT FROM AUTHOR]

The development of research related to the characterization of niobium pentoxide (Nb 2 O 5) has been of great interest in the scientific and commercial community due to promising performances in bio-electrochemical applications, advanced catalysts and corrosive environments. In this work, layers of 250 µm, 350 µm and 550 µm of Nb 2 O 5 were deposited by low-speed flame spray on NiAl-bond coated AISI 1020 steel substrates. The phase transformations of Nb 2 O 5 , which occur during the formation of the layers, were studied as a function of deposited thickness and further correlated with adhesion, abrasion and slurry erosion resistance. X-ray diffraction analyzes of the coatings were performed for the study of the phases in the process. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) with dispersive energy microanalysis (EDS) were used to help microstructural analysis. The adhesive strength of the layers was evaluated by ASTM C633-13 and correlated with abrasion (ASTM G65-16) and slurry erosion wear resistance. From the microscopy analysis, a dense layer was observed with good interconnection at the interface Nb 2 O 5 -NiAl, with presence of pores typical of the thermal spray process. The XRD diffractograms of the niobium oxide coated samples show similar results regardless of the coating thickness (250, 350 and 550 µm) presenting superior compatibility with the hexagonal Nb 2 O 5 and the monoclinic NbO 2.46 (Nb 22 O 54). The significantly higher intensities of the hexagonal Nb 2 O 5 peaks suggest that it is the predominant phase. The thinner coatings, 250 and 350 µm, had higher adhesive strength, with a mean fracture stress of 16.12 MPa and 15.27 MPa, respectively. Nb 2 O 5 thinner coatings showed also higher abrasive wear resistance when compared to "D2" tool steel and "H13" chrome tool steel. The thicker coatings (550 µm) had a mean adhesive strength of 13.73 MPa. From the abrasive wear tests, thicker coatings showed a greater volume loss of 41.18 mm3. The 550 µm coating presented higher slurry erosion resistance at a 30° particle impact angle, with a lower volume loss (12.93 mm3). • We applied niobium pentoxide coatings onto low carbon steel by flame spraying. • We evaluated the influence of coating thickness and phases on wear and adhesion. • Thicker coatings showed a greater volume loss in abrasive and erosive wear tests. • A single hexagonal phase was observed regardless of the coating thickness. [ABSTRACT FROM AUTHOR]

The phenomenon of slurry erosion in hydro turbines and its components is a major challenge. Microwave cladding is a potential surface modification technique to mitigate the effects of slurry erosion. Microwave exposure time during cladding could play an important role on the microstructure and performance of the developed clads. In the present work, Ni + 20 wt% Cr 7 C 3 composite clads were developed on CA6NM hydro turbine steel using microwave cladding technique. The effect of microwave exposure time on clad microstructure and its subsequent effect on slurry erosion characteristics were studied. The developed clads were assessed in terms of their microstructure, phase analysis, nanohardness and fracture toughness using various techniques. Slurry erosion characteristics of the developed clad were studied using a slurry jet erosion test rig. The slurry erosion trials were performed at a jet velocity of 40 m/s with an impact angle of 90° for 120 min. Cumulative weight loss, wear rate and wear mechanisms were assessed to determine the slurry erosion performance of the developed clads. • Influence of exposure time on microstructure and slurry erosion presented. • Exposure time of 35 min results in coarse and rod like structured carbides. • Mechanism of slurry erosion schematically explained. [ABSTRACT FROM AUTHOR]

The regular replacement and maintenance of steel pipes used to transport slurry in oil sands mining and extraction continue to represent a major expense for oil sands operations. Pipeline steels such as API 5 L X65 and X70 are the main materials for the slurry transport system. In our previous work, dual-phase stainless steel showed excellent performance in aeriated (high dissolved oxygen) slurries operated at low to moderate velocities involving erosion-corrosion. However, the benefits of using stainless steel diminish as the oxygen in slurry is depleted or at higher slurry velocities at which mechanical properties, particularly deformation energy or strain-hardening capability, of the steel become more dominant. This article reports our recent studies on erosion-corrosion of high manganese steel at different slurry velocities (3.5 m/s and 5.5 m/s) and different dissolved oxygen levels (0.6 ppm and 3.8 ppm). The erosion-corrosion tests were performed at 60 °C in sand-containing slurry (20% vol. silica) with 500 ppm chloride, which simulated common field situation. Characterization of the steel was carried out with optical and scanning electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction technique, micro-mechanical probe, and electrochemical testing. The performance of the high manganese steel was compared to those of API 5 L pipeline steels commonly used in slurry transport, ASTM A1053 Gr.50 dual-phase ferritic-martensitic stainless steel, and AR400 martensitic hard plate. Results of this investigation demonstrate how the high strain-hardening capability of the high manganese steel produces an outstanding erosion resistance, which is more than two times as high as those of ferritic steels. The results are compared to those obtained through field trials performed in an oil sands coarse tailings pipeline. • High manganese steel exhibits a remarkable erosion-corrosion performance. • Erosion resistance of high manganese exceeds those of AR400 and pipeline steels. • Deformation energy showed the larger influence on the steels erosion resistance. • Field trials of high manganese steel were consistent with laboratory results. [ABSTRACT FROM AUTHOR]

Understanding the wear process has been critical for developing and maintaining engineered systems handling particle-laden flows, such as pipelines, valves, pumps, and mixers. This work explores the use of ultrasound velocimetry for determining the velocity and impact angle of particles projected from a turbulent slurry flow onto a moving target surface. The flow is generated in a slurry pot configuration at four levels of rotational frequency: 1900, 2200, 2500 and 3300 rpm. Acoustic images acquired in the B-mode are processed by Ultrasound Particle Tracking Velocimetry (U-PTV) and Ultrasound Particle Image Velocimetry (U-PIV) to determine the impact velocities and impact angles of individual particles in the radial plane. Particle impacts at velocities higher than the tangential velocity of the rotating axis are observed and named counter-wise impact due to their association with counter-wise vortices impacting in the direction contrary to the translation of the moving surface. The applicability of U-PTV and U-PIV for the study of particle-laden turbulent flow is discussed and a statistical analysis of particle impacts energy is conducted. The counter-wise impacts are found relevant to erosive wear because of their relatively high velocity (upper quartile) and because most of the impact energy is conveyed through the tangential component. • Trajectories of individual particles in turbulent slurry are measured acoustically. • Flow structure in slurry pot includes normal- and counter-wise vortices. • Impacts from counter-wise vortices convey significatively more energy. • Most of the energy is conveyed through the tangential component of impact. • Applicability of the method and algorithms is discussed. [ABSTRACT FROM AUTHOR]

The numerical prediction of the impact erosion produced by slurries is particularly challenging from the modeling point of view, not only due to the complex interactions between the phases, but also because self-induced geometry changes can influence the course of the wear process. The usual methodology for impact erosion estimation, which is based on the Eulerian-Lagrangian description of the slurry flow followed by the application of a single-particle erosion model to each particle-wall impingement, may be able to reproduce the complex physics underlying slurry erosion only at the price of complex algorithms and heavy computation, which is unaffordable in practical applications. In order to overcome these difficulties, an alternative approach was proposed, which involved the steady-state simulation of the slurry flow by an Euler-Euler model followed by the repeated calculation of individual particle trajectories in the proximity of the solid walls and the continuous update of the wear profile. The improved accuracy obtained in the simulation of several abrasive jet impingement experiments reported in the literature make the application of this method to more complex flows very promising. [ABSTRACT FROM AUTHOR]

Hardness has been regarded as a primary parameter for the wear resistance evaluation of metals for a long time. However, because of work-hardening induced by wear, sometimes there is a big difference between the actual wear resistance and the evaluation with the original hardness ( H 1 ). So an experimental hardness test after strain-hardening was suggested, and the effect of this experimental hardness on the evaluation of erosive wear resistance was investigated. Based on the slurry erosion tests of 8 kinds of metals under 90° impingement, a significant positive linear correlation between the erosive wear resistance and the ratio of strain-hardened hardness ( H 2 ) and compressive elastic modulus ( E ) was obtained. And the correlation coefficient ( R 2 ) between the value of erosive wear resistance and H 2 / E ratio increases from 0.61 to 0.89 when the original hardness is substituted by the strain-hardened hardness. Furthermore, the erosive wear resistance of AlCrFeCoNiCu HEA was evaluated by the empirical expression and the difference between the experimental and predicted values is less than 10%. Therefore, the proposed evaluation method with the strain-hardened hardness is practical and effective for the erosive wear resistance evaluation of a candidate metallic material. [ABSTRACT FROM AUTHOR]

The erosion of a surface by a sediment-laden flow is an inherently multiscale phenomenon which includes physical interactions covering many orders of magnitude in both length and time scales. Conforming to the nature of the problem, we propose a novel multiscale model for simulating this complex process. On the one hand, a macroscale model encompassing the whole domain of interest solves the turbulent sediment transport problem. On the other hand, a microscale model simulates the sediment impacts against the surface. A sequential multiscale strategy is used to link the submodels, such that the microscale model provides closure to the macroscale model in terms of the calculated steady state erosion rate and restitution coefficients, therefore reproducing the original coupled problem. The proposed methodology is validated against experimental data for the slurry jet erosion of a copper plate at three impingement angles. Both the global erosion rate and the erosion depth profile are predicted with mean relative errors of 18% compared to the corresponding experimental values, achieving a significant improvement over correlation-based approaches. [ABSTRACT FROM AUTHOR]

Multifunctional coatings were obtained by a sol-gel co-condensation of a fluorinated silane and tetraethoxysilane over activated Halloysite nanotubes (hHNT). They were applied onto epoxy based substrates (neat epoxy or hHNT loaded) with different curing conditions. The coatings characterization showed low friction and high hydrophobicity. The coefficient of friction against stainless steel was 0.1, according to the nanoscratch test and the advancing contact angles reached values in the range 135–145°. The materials were subjected to a slurry erosion test under high speed flow condition and wettability was used to characterize the surface integrity over erosion-cumulative time periods. Fluorine containing coatings exhibited an outstanding resistance to the high speed slurry erosion (HSSE). After 1 h of HSSE test, average advancing contact angles of 145° were measured for the fluorinated samples. The high hydrophobicity of the coatings showed a correlation with the erosion resistance, while the substrate showed no effect. An explanation of the cushioning effect of hydrophobicity upon erosion wear is given, based on wall-detached eddies on the boundary layer. [Display omitted] • Halloysite nanotubes crosslinked with polysilsesquioxane covalent linkages allowed obtaining highly hydrophobic coatings. • Spray coating technique together with a fluorine-containing composition led to high hydrophobicity. • High speed slurry erosion equipment based on a circulating sand/water slurry was developed and tuned up. • Highly hydrophobic-fluorinated coatings were resistant to slurry erosion. [ABSTRACT FROM AUTHOR]

Protective coatings have been gaining prominence in research related to graphene based compounds over the recent years. The present study aims to reveal the novel anti-corrosive properties of the coatings achieved by co-depositing the carbon allotropes. Electroless Ni-P-rGO coatings were successfully obtained on low carbon steel substrates by adding various concentrations of rGO particles to the conventional electroless Ni-P bath. The coated specimens were characterized for its morphology and composition corroborated by X-ray diffraction and microhardness analysis. The corrosion and erosion corrosion behaviour of the Electroless Ni-P-rGO coatings were studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt% sodium chloride solution. The erosion corrosion behaviour of the coatings for different concentrations of rGO particles was examined using a slurry pot tester. The addition of rGO particles had considerably improved the corrosion and erosion resistance and the best results were achieved at an optimum concentration of 50 mg/L of rGO in the bath. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs) represent a new paradigm of structural alloys comprising of multiple principal elements in equimolar or near-equimolar concentration. The superior corrosion and oxidation resistance of HEAs at high temperature make them attractive for several structural applications. In this context, erosion behavior of HEAs has been largely unexplored. In this study, the slurry erosion performance of single phase Al 0.1 CoCrFeNi high entropy alloy was investigated. For comparison, mild steel and stainless steel (SS316L) were also investigated under similar conditions. The slurry erosion was conducted at different impingement angles and at a constant velocity of 20 m/s. The microstructural and mechanical characterization were conducted using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), nanoindentation and micro-hardness testing. Similar to the mild steel and stainless steel, HEA also showed ductile mode of erosion. The erosion rate for HEA was found to be higher compared to stainless steel, however in spite of lower tensile strength and hardness, HEA exhibited higher erosion resistance compared to mild steel. The high erosion resistance of HEA compared to mild steel is explained on the basis of its work hardening behavior, low stacking fault energy, and superior corrosion resistance. Erosion response of the investigated materials showed significant correlation with ultimate strength and ultimate resilience. In depth analysis of the eroded HEA samples showed ploughing as the prominent material removal mechanism at oblique angles compared to micro-cutting for SS316L and mild steel. In contrast, highly deformed and work-hardened platelets were observed at normal impingement angle for all materials. [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]

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]

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]

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]

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]

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]

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]

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]

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]

Titanium is used as a construction material under the most demanding process conditions in hydrometallurgical industry where process equipment is subjected to erosion–corrosion. In order to understand complex erosion–corrosion behavior of titanium its erosion behavior needs to be understood first. Titanium (ASTM Grade 2) was eroded in a slurry pot tester under normal impact using nine different erodants with varying particle size and shape. The measured weight losses were compared to those of 316L stainless steel obtained under similar experimental conditions. The results showed that various erodants damaged the titanium surface as a result of several mechanisms including microcutting and crater formation. The induced weight loss was not solely dependent on the kinetic energy of the particles but their shape was also found to have an effect. Titanium showed slightly higher mass loss than 316L. The relative ranking of the severity of the erodants was found to be the same for titanium as for 316L stainless steel. [ABSTRACT FROM AUTHOR]

This study is an investigation of the effect of impingement angle on slurry erosion-corrosion of Stellite 6 manufactured by sand casting, lost wax casting and SS316. The tests were performed using an impingement rig in which a slurry with 3.5% NaCl and 1.177 g/l suspended angular sand particles at 19 m/s were recirculated for 1 h. The results were obtained for angles of 20°, 45°, 60° and 90° to the exposed surface. Post-experimental analysis using light microscopy, surface profiling and SEM assisted with clarification of the wear mechanisms and assessment of the severity of surface damage. Stellite 6 consistently exhibited superior wear resistance compared with SS316. The most severe regime for SS316 was experienced at low angle of impingement, 45°, due to its ductility. Alternatively, the brittle network of chromium carbides showed significant impact on the behavior of cast Stellite 6 under solid-liquid impingement with the most critical erosion-corrosion damage occurring at 60°. [ABSTRACT FROM AUTHOR]

The erosion resistance of several austenitic and duplex stainless steel grades was investigated with slurry pot tests using erodents with different size fractions and properties. Ranking of the studied stainless steel grades was rather systematic despite the type and properties of the erodent. The results revealed that, on average, duplex stainless steel grades showed better erosion resistance in aqueous slurries than austenitic grades whatever the erodent. Out of the austenitic grades, 316L had higher erosion resistance than that of 904L when tested with high wear-inducing erodents. Regarding the duplex grades, superduplex grade 2507 had the best erosion resistance. The kinetic energy of the erodents explained a substantial amount of the measured erosion mass loss, but chromite for instance was more wear-inducing than expected on the basis of kinetic energy due to the angularity of the particles. Wear surface features of the austenitic grades differed from those of the duplex grades. Reasons for the observed behavior are discussed. [ABSTRACT FROM AUTHOR]

Erosion and erosion–corrosion behaviors of the Al–brass alloy were investigated using a slurry impingement rig at a velocity of 6 m/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 6 m/s. [ABSTRACT FROM AUTHOR]

The extremely altered topmost surface layer, known as the white layer, formed in a medium-carbon low-alloy steel as result of impacts by angular 10–12 mm granite particles during the slurry erosion process is comprehensively investigated. For this purpose, the characteristics, morphology, and formation mechanism of this white layer are described based on the microstructural observations using optical, scanning and transmission electron microscopies as well as nanoindentation hardness measurements and modelling of surface deformation. The white layer exhibits a nanocrystalline structure consisting of ultrafine grains with an average size of 200 nm. It has a nanohardness level of around 10.1 GPa, considerably higher than that of untempered martensitic bulk material (5.7 GPa) achieved by an induction hardening treatment. The results showed that during the high-speed slurry erosion process, solid particle impacts brought forth conditions of high strain, high strain rate, and multi-directional strain paths. This promoted formation of a cell-type structure at first and later, after increasing the number of impacts, development of subgrains following by subgrain rotation and eventually formation of a nanocrystalline structure with ultra-high hardness. The model confirmed that high strain conditions - much higher than required for the onset of plastic deformation - can be achieved on the surface resulting in severe microstructural and property changes during the slurry erosion test. • The microstructural characteristics of white layer are fully pictured. • White layer showed a nanocrystalline structure with extremely high hardness level. • White layer formed mainly by a mechanically induced grain refinement mechanism. • FE modelling revealed high straining of the surface by erosive solid particle impacts. [ABSTRACT FROM AUTHOR]

Robot polishing is increasingly being used in the production of high-end glass work pieces such as astronomy mirrors, lithography mirrors, laser gyroscopes or high-precision coordinate measuring machines. The quality of optical components such as lenses or mirrors can be described by shape errors and surface roughness. Whilst the trend towards sub nanometre level surfaces finishes and features progresses, matching both form and finish coherently in complex parts remains a major challenge. With increasing optic sizes, the stability of the polishing process becomes more and more important. Polishing agent nozzles supply the polishing process with sufficient polishing agent and it is assumed that this slurry erosion has an influence on the material removal. To investigate this, a static test set-up was built. The primary aim of this paper is to point out and raise awareness of the problem of slurry erosion in glass polishing and the influence of slurry erosion by conventional polishing nozzles is shown. From an angle of 30°, the nozzle turns into a fluid jet tool and removes material independently. • Raising awareness of the problem of abrasion caused by polishing slurry nozzles. • Verification for a more stable process by choosing a correct angle of the nozzle. • Detection of further challenges (e.g. nozzle wear) and recommendations for solutions for the presented challenges. [ABSTRACT FROM AUTHOR]

The slurry erosion behavior of a zirconium based bulk metallic glass, Zr44Ti11Cu10Ni10Be25, was evaluated in this study. Slurry erosion tests were carried out using a non-circulating type test rig at impingement angles of 30°, 60°, and 90°. Commonly used hydroturbine steel was evaluated under the same test conditions. At 30° impingement angle, the metallic glass demonstrated nearly 2.6 times higher erosion resistance compared to the steel. At normal impingement, the metallic glass was marginally better. Lower erosion rates of the bulk metallic glass at oblique impingement angles was attributed to its significantly higher hardness and deformation induced partial devitrification. For normal impingement, material was removed in the form of fragments from highly strained platelets due to limited plasticity of bulk metallic glasses. The metallic glass demonstrated a brittle mode of erosion with higher erosion rate at higher angle of impingement. In contrast, hydroturbine steel showed ductile mode of erosion under the same test conditions. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, slurry and dry erosion behavior of HVOF sprayed WC–CoCr cermet coatings has been studied. The coatings were developed using the powders feedstock having WC grains in conventional and fine structured sizes. The slurry erosion testing was performed using a laboratory made pot-type slurry erosion tester. The dry erosion testing was carried out using air-jet erosion test rig (ASTM G76-07), at an impact velocity of 60m/s and 90° impact angle. The rate of dry erosion was significantly high as compared to that of slurry erosion and it was mainly due to the particle-target impact velocities and impact angle. The mechanism of material removal in slurry and dry erosion was studied and discussed on microstructural investigations and was found to be different in both the erosion conditions. The morphology of eroded surface shows crater, lip and groove formation in the binder matrix, carbide fracturing, chipping, and pullout as visible mechanism of material removal. It was observed that the cermet coating with fine WC grain exhibits higher erosion resistance as compared to conventional cermet coating due to its improved properties like micro-hardness and fracture toughness. [Copyright &y& Elsevier]

Abstract: Components exposed to the flow of liquid solutions containing hard particles experience significant material loss. For defined slurry conditions, the extent of damage to the components depends upon their microstructure and the slurry particle impingement angles. This paper presents the research work carried on to develop a gas metal arc welding (GMAW) clad overlay that resists slurry erosion at both low and high particle angles. GMAW overlays containing hard primary Fe2B crystals in a supporting matrix enriched in molybdenum, carbon and silicon have been considered. Cored wires of specific compositions deposited with adapted welding parameters produce weld overlays presenting a peculiar microstructure. These iron boride-based overlays contain fine elongated boride crystals aligned mainly perpendicularly to the wearing surface. This peculiar microstructure is responsible for the outstanding slurry erosion resistance observed at both impinging angles of 30° and 90°. These iron boride-based overlays present a slurry erosion resistance at low and high impinging angles far beyond that observed with known materials including chromium carbide overlays. [Copyright &y& Elsevier]

Abstract: In this study, the erosion of Ti(C, N)-based cermets with varying Mo2C content was tested in a slurry solution containing 5wt% H2SO4 and 5wt% Al2O3 particles. Erosion and corrosion of the cermet causes the removal of the Ni binder to occur, exposing the Ti(C, N) grains as well as the microcracks, carbide particle fracture, debonding of particles and corrosion within the binder. The microcracks and fracture decrease with Mo2C addition, while the erosion–corrosion resistance of Ti(C, N)-based cermets was greatly improved with 5wt% Mo2C addition and slightly decreased with the addition of 10wt% or more Mo2C. [Copyright &y& Elsevier]

Abstract: Hydroturbine components generally suffer from severe wear due to slurry erosion caused by solid particles entrained in the flowing water. High-velocity oxy-fuel (HVOF) spray process is known for depositing protective coatings on the materials. In this work, WC–10Co–4Cr and Al2O3+13TiO2 coatings were deposited on CF8M turbine steel by HVOF spray process and studied with regard to their performance under slurry erosion conditions. High speed erosion test rig was used for slurry erosion tests and effect of three parameters namely average particle size, speed (rpm) and slurry concentration on slurry erosion of these materials was investigated. The bare steel and Al2O3+13TiO2 coating followed ductile and brittle mechanisms respectively under slurry erosion, whereas the WC–10Co–4Cr coating exhibited mixed behaviour (mainly ductile). WC–10Co–4Cr coating was found to be useful to increase the slurry erosion resistance of steel remarkably. [Copyright &y& Elsevier]

Abstract: Tribological behaviors of plasma-sprayed conventional and nanostructured Cr2O3–3%TiO2 ceramic coatings (i.e., CC3T and NC3T, respectively) using pin on disc type dry sliding and pot type slurry erosion test were investigated in the present work. The experimental results indicated that there were two main wear mechanisms, plastic smearing and adhesive tearing, in the worn coatings under dry sliding. Plastic smearing corresponded to a lower average friction coefficient and wear rate, while adhesive tearing corresponded to higher values. The erosive environment selected for the slurry erosion experiments include 10, 20 and 30% of SiO2 slurry concentrations in water with particle size 75–106μm. The main damage mechanism observed in all the coatings submitted to slurry erosion were the formation and propagation of brittle cracks resulting in the detachment of coating surface material. Microstructural investigation was also carried to investigate the wear and erosion mechanism of the coatings using FE-SEM and EDS analysis. Properties like microhardness and porosity were also investigated for these coatings. Tribological performance of NC3T was better as compared to CC3T as observed in the present work. [Copyright &y& Elsevier]