The anti-slurry erosion properties of polyethylene for sewerage pipe use

Sewerage systems are more common in Japan. The pipes and fittings in the systems are exposed not only to a corrosive environment, but also to the impact by solid particles contained in mud drains, resulting in an erosive wear on the surface. A strategy for coping with these problems involves replacing the more traditionally used iron and steel pipes with polymeric materials, which have excellent anti-corrosion properties. In this study, a slurry erosion test were carried out using a jet-in-slit apparatus on seven types of polyethylenes, three other types of polymers, and two types of iron and steels, thoroughly taking into account the fact that erosion damage is highly dependent on the impact angle of the particles. As a result, all the polyethylenes proved to have excellent anti-erosion properties, compared with the other materials over the entire range of particle impact angle. Further, a model was proposed to account the impact angle dependency of the erosion damage. The model aided in clarifying the reasons why the erosion rate of the polyethylenes is satisfactorily correlated with a complex parameter in which the fracture energy and the elastic modulus are combined.     

Solid particle erosion of diamond coatings under non-normal impact angles

This paper describes an erosion study, which examines the effect of impact angle on the erosion behaviour of diamond coatings deposited on tungsten substrates by chemical vapour deposition (CVD). The coatings were 37–60 μm in thickness and were erosion tested using angular silica sand with a mean diameter of 194 μm at a particle velocity of 268 m s⁻¹. The impact angles used were 30, 45, 60 and 90°. The results show that the damage features, termed “pin-holes” are generated at all angles, though the number of impacts required for pin-hole initiation is significantly increased at lower angles. This work provides useful information in attempting to explain the mechanism by which damage is generated during the high velocity sand erosion of CVD diamond.     

Determination of particle impacts and impact energy in the erosion of X65 carbon steel using acoustic emission technique

An in-situ acoustic emission (AE) monitoring technique has been implemented in a submerged jet impingement (SIJ) system in an effort to investigate the effect of sand particle impact on the degradation mechanism of X65 carbon steel pipeline material in erosion conditions.A detailed analysis of the acoustic events' count rate enabled the number of impacts per second to be quantified for a range of flow velocities (7, 10, 15 m/s) and solid loadings (0, 50, 200, 500 mg/L) in a nitrogen-saturated solution at 50 °C. The number of impacts obtained from acoustic signals showed a strong agreement with theoretical prediction for flow velocities 7 and 10 m/s. A deviation between practical readings and theory is observed for flow velocity of 15 m/s which may be due to error from detected emissions of multiple rebounded particles.Computational fluid dynamics (CFD) was used in conjunction with particle tracking to model the impingement system and predict the velocity and impact angle distribution on the surface of the sample. Data was used to predict the kinetic energy of the impacts and was correlated with the measured AE energy and material loss from gravimetric analysis. The results demonstrate that AE is a useful technique for quantifying and predicting the erosion damage of X65 pipeline material in an erosion–corrosion environment.     

Understanding particle dynamics in erosion testers—A review of influences of particle movement on erosion test conditions

An understanding of particle dynamics is important when determining material erosive wear in any erosion tester, because particle impact conditions are primarily influenced by particle acceleration. A better understanding of particle dynamics in the testers will aid the control of erosion test conditions and therefore improve the accuracy of measurement. In this paper, particle dynamics in the two most popular erosion testers, the centrifugal erosion tester and the gas-blast erosion tester, has been discussed in detail. Mechanisms of particle acceleration in the two types of testers were explored and computational models of particle dynamics were described briefly. A review of the experimental determination of important characteristics of particle dynamics (such as particle velocity, particle trajectory, particle dispersion and particle rotation) showed how they influenced particle movement and therefore the particle impact conditions. In addition, comparison of the particle dynamics in the two types of erosion testers showed that differences of particle acceleration may lead to significantly different results at identical pre-set test conditions. It may be concluded that it is not possible to directly compare the results obtained in different types of erosion testers even under notionally identical test conditions.     

Solid particle erosion of CFRP composite with different laminate orientations

The solid particle erosion behavior of epoxy base unidirectional and multidirectional carbon fiber reinforced plastic composites was investigated. The erosion rates of these composites were evaluated at various impingement angles (15–90°) with a particle velocity of 70 m/s. Irregular SiC particles with an average diameter of 80 μm was used. The dependence of impingement angle on the erosive wear resembled the conventional ductile behavior with maximum erosion rate at 15–30° impingement angle. The erosion rate of unidirectional composites at acute impingement angle was higher for [90] than for [45] and [0] while the difference disappeared at normal impingement angle (90°). On the other hand, the erosion rates of multidirectional laminated composites ([0/90], [45/−45], [90/30/−30] and [0/60/−60]) were not much influenced by the fiber orientation except for 15° impingement angle.     

Influence of particle impact conditions and temperature on erosion-oxidation of steels at elevated temperatures

The behaviour of four steels that are used in fluidized-bed boilers (16Mo3, T91, 304L and 253MA) has been studied in air (oxidation) and under impacts by sand particles in air (erosion-oxidation) at 350-650 °C in an extensive test programme and their performance compared in terms of the resulting weight changes and surface appearances.The results show that the oxidation rates for the steels increase with temperature but decrease with increases in chromium contents of the steels, as expected. Through oxidation rate, temperature has a significant influence on overall weight changes during combined erosion-oxidation, with material losses often increasing with temperature. The lowest particle velocities often cause deposition of particle debris and some weight gains, whereas the highest velocities cause essentially loss of material. Ductile erosion behaviour is observed under most conditions, with higher material losses at a shallow than at a steep impact angle, but the overall angle-dependency slightly changes with increase in temperature. The explanations for these observations are discussed in this paper. Furthermore, materials selection maps are constructed from the results generated, demonstrating that choosing the most highly alloyed material available is not necessarily the best rationale for materials selection.     

Solid particle erosion behaviour of Ti6Al4V alloy

Abstract

The effects of particle impingement angle, impingement velocity and erodent particle size on the erosion rate and surface morphology of the Ti6Al4V alloy have been investigated comprehensively in order to evaluate solid particle erosion behaviour of Ti6Al4V alloy. Samples were eroded in a specially designed sandblasting system under various parameters using alumina (Al₂O₃) erodent particles. Surface morphology investigations were examined by scanning electron microscope using various analysis and modes (energy dispersive X-ray analysis, elemental mapping and compositional contrast). Ti6Al4V alloy showed ductile behaviour with a maximum erosion rate at 30° impingement angle. Erosion rate of Ti6Al4V alloy increased with increases in velocity and decreased with increases in erodent particle size. Scanning electron microscopy investigations of eroded surfaces of Ti6Al4V alloy samples reveal the dominant erosion mechanism such as microploughing, microcutting and plastic deformation. Embedded erodent particles on the surfaces of Ti6Al4V alloy nearly at all particle impingement angles and velocities were clearly detected.     

Some aspects of solid particle erosion of cermets

The erosive wear resistance of cermets with different composition, structure and properties has been investigated. It was shown that the erosive wear resistance of cermets can not be estimated only by hardness, characterizing resistance to penetration. The differences in wear resistance between cermet materials with equal hardness levels can be attributed to differences in their resistance to fracture and fracture toughness. The mechanism of erosion depends first on testing conditions. The present paper discusses some features of the material removal process during particle-wall collision. Systematic studies of the influence of the impact variables on the collision process have been carried out.     

Solid particle erosion of unidirectional fibre reinforced thermoplastic composites

In the present study, the solid particle erosion behaviour of neat PEEK matrix and unidirectional glass fibre (GF) and carbon fibre (CF) reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) composites has been studied. The erosion experiments have been carried out by using silica sand particles (200 ± 50 μm) as an erodent. Steady state erosion rates of these composites have been evaluated at different impact angles and impact velocities. The neat PEEK exhibited peak erosion rate at 30° impingement angle whereas the composites exhibited a semi-ductile behaviour with peak erosion rate at 60° impact angle. The erosion rate of the glass fibre reinforced composites was higher than that of the carbon fibre reinforced composites. The results show that the fibre orientation has a significant influence on erosion rate only at lower impact angles. The erosion rate of the composites was higher when the particles impact perpendicular to the fibre direction than parallel to the fibres. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.     

Experimental verification of a model of erosion due to the impact of rigid single angular particles on fully plastic targets

A previously described rigid-plastic model of the erosion of ductile targets by the impact of single angular particles was experimentally verified over a wide range of particle angularities, incident angles of attack, and incident orientation angles. The model assumes that the particle is perfectly rigid and thus is non-deforming, while the target material response is fully plastic, so that elastic rebound effects are neglected.Measurements of particle rebound kinematics, crater volume, and crater shape revealed generally good agreement with those predicted by the rigid-plastic model, and erosion mechanisms resulting from particles tumbling either forwards or backwards, were identified. For highly angular particles, target material removal sometimes occurred due to tunnelling of the particles below the target surface, leading to early break-off of a machined chip, behaviour that could not be predicted by the rigid-plastic model. Besides providing insights into fundamental erosion mechanisms, the results of the present study can be used to predict particle rebound kinematics, crucial for simulations of erosive streams which take into account interference between incident and rebounding particles.     

Elasto-plastic impact of a rotating link with a massive surface

This study presents the impact with friction of a rigid or a flexible body against a half-space, each with a small region of contact compliance where the compliance is obtained from the Jackson and Green theory. The model consists of a system of nonlinear differential equations which considers a nonlinear contact force as well as frictional effects at the contacting end, and allows one to predict the motion after the impact. The initial incidence angle, the initial impact velocity, and the contact radius of the link are found to influence the coefficient of restitution with friction. Analytical and experimental results were compared to establish the accuracy of the model.     

Measurements of plastic strain around indentations caused by the impact of round and angular particles, and the origin of erosion

The aim of this paper is to examine plastic strain distributions around indentations and to consider the mechanisms of erosion damage caused by solid particle impact. A WC ball and an angular SiC particle of 3 mm in diameter were used to compare the effect of particle shape on plastic strain. Measurements of principal shearing strain distributions around the indentations were performed on surfaces of aluminum, iron and cast iron at impact angles of 20°, 30°, 40°, 60° and 90° at impact velocities from 50 to 200 m s⁻¹. It was found that the impact angle dependence was roughly consistent with the maximum principal shearing strain and erosion damage data, which have been published in previous papers and obtained during additional works in this study. The surface topography of the impact craters suggested that depth, contact area and volume of indentation are affected by the particle density and the hardness of both particle and target material. Measurements of volume ratio of lips to craters proved that material removal did not necessarily occur at a single impact of the WC ball, but occurred at the impact of the angular SiC particle at low impact angles. It is concluded that the origin of erosion is probably attributed to the conjoint actions of high plastic strains followed by subsequent removal and the cutting process caused by particle impact.     

Correlation between solid particle erosion of cermets and particle impact dynamics

Since the erosion rate depends on energy exchange between particle and material, a reformulation and solution of the equations of two solid bodies collision is presented and adapted to the calculation of the energy absorbed by a material surface during impact of a spherical particle onto a plain target. It has been observed that energy loss is a strong function of dynamic coefficients named as coefficient of velocity restitution after impact, k, and coefficient of dynamic friction, f. The new method and experimental equipment for the coefficients determination are described. It was shown that energy consumption during application may be an appropriate guide for the material selection in the conditions of erosive wear.     

Analytical model of particle interference effects in divergent erosive jets

An analytical model that describes the interference, due to collisions between an incident diverging axi-symmetric jet of spherical particles, and those rebounding from a flat surface oriented perpendicular to the jet axis (i.e., normal incidence), is presented. The model can accommodate non-uniform incident particle velocity and spatial distribution, variation in particle spacing along the jet axis, and non-elastic frictional impact kinematics. The model can be used to estimate interference effects at high flux, and to obtain the critical flux below which a given level of particle interference will occur in a solid particle erosion test. Because the equations that predict the level of interference can be solved in closed form, with the exception of an integral which must be solved numerically, implementation in erosion models is also possible. For the case of an incident jet typically used in abrasive jet micromachining applications, the model is validated against an existing computer model for a wide variety of conditions, with excellent agreement.     

Design and performance of a high velocity air–sand jet impingement erosion facility

This paper describes the design, construction and capabilities of a high velocity air–sand erosion rig. It has been designed with the aid of computational fluid dynamics to approximately simulate the erosion conditions often experienced by subsea choke valves used in the offshore oil industry. It has also been designed to evaluate the erosion performance of CVD diamond coatings at sonic velocity. The rig is of the gas-blast design in which solid particles, typically sand 60–660 μm in size, are injected into a high velocity air stream and accelerated down a 16-mm-diameter tube, 1 m in length, before striking the sample under test. Tests can be carried out with particle velocities of up to 340 m/s under a wide range of sand fluxes, impact angles and standoff distances. The results of pressure, velocity and sand flux calibration work are described. In addition, preliminary experimental data on tests carried out on mild steel, bulk and sprayed tungsten carbide are also presented. The flexibility of the air–sand rig allows the erosion behaviour of materials to be studied under a wide range of conditions.     

Erratum to “The effect of particle size on the erosion of a ductile material at the low particle size limit” [Wear 233–235 (1999) 727–736]

The intrinsic particle size dependence of erosion rate was investigated in the absence of aerodynamic effects. An apparatus was designed to impact small particles on metallic substrates at normal incidence in vacuum. Two types of target materials, Cu–30% Zn and pure Ti, were impacted with SiO₂ particles with average diameters of 2, 5 and 25 μm. The velocity of impact was 12 m/s. Damage processes induced by single particles were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). This latter technique allowed for the measurement of impact profiles, both of the cut surfaces and the associated displaced material pile-ups. The impacts produced were, in many cases, asymmetrical, and the asymmetries appeared to be related to the orientation of the impacted surface. The appearance of the damage was essentially the same for all three sizes of the erodent, and for two different substrate materials having different crystal structures.     

Relationship between the effects of velocity and alloy corrosion resistance in erosion-corrosion environments at elevated temperatures

Erosion-corrosion by either solid particle or liquid impact occurs in a wide variety of industrial environments which range from coal conversion processes to steam turbines in nuclear power generation. The effects of erosion-corrosion depend on properties of the particle, the target and the nature of the corrosion environment. Various regimes of erosion-corrosion interaction have been identified, ranging from “erosion-dominated” (erosion of the substrate) to “corrosion-dominated” (erosion of the corrosion product).

In studies of erosion-corrosion, the effects of impact velocity are generally not well understood. In some environments in which corrosion occurs, high velocity exponents have been reported, while, in others, the values are close to 1. In addition, the effects of alloy corrosion resistance in environments of different velocities have been puzzling with differences in the exponents reported, as alloy corrosion resistance is increased.

This paper considers the effect of velocity for various erosion-corrosion studies from the literature. The effects of alloy corrosion resistance for such results are evaluated. Some general provisos for the interpretation of the effects of velocity will be made for alloys of different corrosion resistance in erosion-corrosion environments. It is shown that relative erosion-corrosion resistance of alloys in one environment cannot be used arbitrarily to predict resistance in other environments, particularly if parameters such as velocity are varied significantly.     

The effect of inter-particle collisions in erosive streams on the distribution of energy flux incident to a flat surface

The effect of interference between incident spheres in a stream, and those rebounding from a flat surface on the distribution of incident energy flux to the surface was determined for a typical erosion testing apparatus using a previously described computer simulation. A dimensional analysis allowed for presentation of the results in a generalized format, so that they could be used to assess interference effects under varying input parameters. Under conditions in which less than 50% of the incident particles underwent inter-particle collisions, expressions describing the impact velocity, the striking angle and the spatial distribution of impacting particles were derived as a function of process parameters. Compared to the no-interference case, the incident energy flux was found to significantly decrease near the center of the impacting stream, but increase far from the centre, when incident parameters that tended to reduce the space between particles in the incident stream were varied. Implications for erosion test ing and expected initial erosion profile were discussed.     

A study on the effect of surface orientation on erosion wear of flat specimens moving in a solid-liquid suspension

Wear characteristics of a ductile material, namely, brass have been investigated by orienting the flat specimens at different orientations relative to the velocity direction in a pot tester containing a solid-liquid suspension. The erosion behavior has been studied at various orientation angles, defined as the angle between the tangent to the plane surface and its velocity. Results at different orientation angles show that the wear at any orientation angle increases with increase in velocity and particle size but decreases with increase in solid concentration. It is also seen that the wear at various operating conditions increases with increase in the orientation angle till 30° attaining the maximum value and then decreases up to 90°. It is further observed that the maximum wear is around 3-4.5 times higher than the surface wear measured at 90° orientation angle.     

Effects of the impact angle variations on the erosion rate of glass in powder blasting process

Sandblasting, a conventional technique which is used for paint or scale removing, deburring, and glass decorating, has recently been developed into a powder blasting technique for brittle materials capable of producing micro-structures larger than 100 m. This article describes an investigation of the effects of the impact angle of particles, the scanning times, and the standoff distance on the surface roughness, the weight-loss rate of samples with no mask, and the wall profile and over-etching of samples with different mask patterns in powder blasting of soda-lime glass. The parameters are the various impact angles between 50 and 90°, the scanning times of a nozzle up to 40, and the standoff distances between 70 and 100 mm. The widths of the mask pattern are 0.2 mm, 0.5 mm, and 1 mm. The powder used is Al2O3 sharp particles, WA#600. The mass flow rate of powder during the erosion test is constant at 175 g/min and the blasting pressure of the powder is 0.2 Mpa. After a series of necessary experiments are performed, the results are investigated and analysed. As a result, a fundamental basis is established that can be applied to powder blasting to produce micro-mechanical parts of glass.