Slurry Erosion–Corrosion of Carburized AISI 5117 Steel

The erosion–corrosion of carburized and untreated low alloy steel (AISI 5117) has been investigated using slurry whirling-arm test rig. Erosion–corrosion tests were carried out in slurries composed of sand particles and either tap water or 3 % NaCl solution. The tests were carried out with particles concentration of 1 wt% and slurry stream impact velocity of 15 m/s. Silica sand having a nominal size range of 250–355 μm was used as an erodent. It has been shown that the erosion and erosion–corrosion resistance of AISI 5117 low alloy steel can be effectively improved by carburizing for all impact angles. However, the effectiveness of carburizing was the highest for an impact angle of 45°, where the erosion and erosion–corrosion resistance were increased by 60–40 %, respectively, compared with that of the untreated material. The results showed that the treated and untreated specimens behaved as ductile materials under erosion and erosion–corrosion tests, and the maximum mass loss occurred at an impact angle of 45°. SEM analysis showed that the erosion tracks developed on the untreated specimens were wider and deeper than that formed on the carburized specimens for erosion and erosion–corrosion tests.     

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.     

Sand-water slurry erosion of carburized AISI 8620 steel

The erosion behavior of carburized AISI 8620 steel for sand slurry service was investigated. The jet impingement type of test was used where sand slurry is directed at flat specimens to determine the erosion rates and mechanism of erosion. The effects of steel heat treatments, slurry velocities and particle concentrations on erosion rates were investigated.     

Slurry wear properties of pump lining materials

In order to study the slurry wear properties of elastomeric lining materials for sand, sludge and sewage pumps, several tests were carried out under various test conditions with a slurry jet device and prototype pump. Preliminary tests were done with 13 materials including polymers, metals and ceramic coatings. Polyurethane, fluid elastomer and rubber showed good wear resistance compared with the hard metals, and were examined in detail. The test conditions were as follows: jet velocity v (8–25 m s⁻¹), impingement angle (10°−90°), mean diameter of silica sand d (42–415 μm), and sand concentration by weight c (0.1–7 wt.%). The slurry wear rates of the polyurethane and the fluid elastomer were maximum at the impingement angle of approximately 30°. The rubber showed almost the same wear rate regardless of impingement angle. The slurry were rate increased according to a power law of the jet velocity above a critical velocity and sand concentration. As the particle size increased above a critical size at the same weight concentration, the wear rate first increased but then decreased. The influence of impingement variables and particle variables observed using both test methods shows a similar tendency for each lining material, so the slurry wear loss can be described with a single empirical equation. Comparing the slurry wear resistance of three lining materials, the polyurethane showed the lowest resistance because it contained many pores which were produced during the lining process. The rubber showed the highest slurry wear resistance which is probably related to its high tear strength.     

Corrosion–erosion wear behaviors of 13Cr24Mn0.44N stainless steel in saline–sand slurry

The corrosion–erosion wear behaviors of austenitic stainless steels, 316L and 13Cr24Mn0.44N, were investigated in water–sand slurry and saline–sand slurry, respectively. The corrosion–erosion wear mass-loss was measured to evaluate the influence of medium and materials. The worn surface and corrosion–erosion wear mechanism were analyzed using a scanning electron microscopy and a non-contact optical profilometer. Results show that the corrosion–erosion wear mass-loss of 13Cr24Mn0.44N is lower than that of 316L in both the slurries. The relative wear resistance increases with the increasing of the impingement velocity and arrives at maximum of 1.6. The dominant wear mechanism of 13Cr24Mn0.44N is abrasive wear in the water–sand slurry, whereas it becomes abrasive wear associated with little corrosive pitting in the saline–sand slurry. As the impingement velocity increased all the synergism ratios exhibit a tendency of increase, among which the synergism ratio of 13Cr24Mn0.44N is always lower than that of 316L at any given velocity. The results indicate that 13Cr24Mn0.44N possesses a predominant anti-corrosion–erosion wear property.     

Erosive wear behaviour of weld hardfacing high chromium cast irons: effect of erodent particles

Five commercial hardfacing high chromium cast iron alloys were deposited by flux cored arc-welding method. The solid particle erosion studies were carried out using air blast type erosion test rig with 125–150 μm cement clinker, 125–150 μm blast furnace sinter, 100–150 μm silica sand and 125–150 μm alumina particles at a velocity of 50 m s⁻¹ and at impingement angles of 15–90°. The observed erosion rates were rationalised in terms of relative hardness of erodent particles and ability of erodent particle to cause gross fracture of the carbides. The dependence of erosion rate on impingement angle was found to be quite weak for hardfacing high chromium cast iron alloys. However, significant differences were observed in the ranking of the alloys when eroded with different erodent particles. The presence of large volume fraction of carbides proved to be beneficial to the erosion resistance when the erodent particle were softer than the carbides. With silica sand particles at normal impact and with alumina particles large volume fraction of carbides proved detrimental to the erosion resistance. The operating erosion mechanisms involved small-scale chipping, edge effect, indentation and fracture and fatigue.     

Electrochemical investigation of erosion-corrosion using a slurry pot erosion tester

The aim of this paper is to use a modified slurry pot erosion tester to perform in-situ electrochemical measurements during solid particle impingement to investigate the effects of velocity, sand size and sand concentration on a passive metal (UNS S31603). Samples are subjected to a set of erosion-corrosion experiments. The electrochemical response of UNS S31603 to the test parameters is plotted and compared to develop an understanding of the erosion-corrosion process. The current trend with variation of test parameters has been explained by an erosion enhanced corrosion synergistic effect. The current transients associated with depassivation and repassivation during solid particle impingement are observed through electrochemical noise measurements. It was observed that the increase in velocity and sand concentration increased the current levels during erosion-corrosion. However, the increase in sand size had a more complex response. Single particle impact experiments conducted revealed that the peak corrosion current and the repassivation time increased with increase in velocity. A linear trend was seen between the peak current and the kinetic energy. A second-order exponential decay was fitted to the repassivation kinetics of the single particle impact. SEM has been used to develop a mechanistic understanding of erosion-corrosion. The surface scars reveal that the depth of the craters and the length of the lips increase with increase in velocity. Micro-cracks also appear on these lips, believed to be due to corrosive action attacking the roots of these lips.     

Some Coriolis slurry erosion test developments

The Coriolis test has developed into a useful way of evaluating the slurry erosion behaviour of materials. Wear mapping has revealed some sensitivity to test conditions so both the tester and test procedures continue to evolve. Experiments with very dilute model slurries comprising a ‘pinch’ of glass beads, or a single glass bead, gave information on bead contact depth and normal component of impingement velocities which confirmed previous theoretical predictions that erodent particles interact with the specimen in a series of low angle impacts. The superior discriminating ability of the Coriolis slurry erosion test is due to the lower interaction intensity of erodent particles with target surfaces compared to that in slurry jet testing.     

Characterization of erosion of gas pipelines by dry sand

In oil and gas industry, the economic considerations determine the selection of low cost materials, in general, carbon steel, for pipelines. However, another type of deformation that is not well understood is its erosion resistance. The objective of this study was to investigate the factors affecting the erosion of carbon steel in a dry sand stream. In this work, a laboratory built test rig was used to erode representative carbon steel plates with accelerated sand streams. The results revealed that the normal incidence sand stream of larger particles and higher impact velocities causes more erosion of the carbon steel. The highest erosion rate of 6.75 ± 0.16 was predicted at an impact angle of 90°, which was three times higher than the erosion rate at impact angle of 30°. Similarly, the erosion caused by the smaller particles was not as severe as the larger particles. The cross-section profiles revealed that the crater depth was increased from 7° to 32.8° with an increase in sand size from 200 µm to 600 µm. The deepest crater of 32.8° was induced by the largest sand size of 600 µm.     

Erosion of metals by flyash particles

The erosion of metal targets by flyash from power station electrostatic precipitators was investigated using a novel test rig. Targets of BG303 stainless steel and HE30 aluminium were used. The effects of target temperature and angle of impingement were studied. The size of particles used was less than 66 μm. The rig utilizes a tube with a fine bore to accelerate particles borne by an air flow; the air flow is then separated from the particle stream with a simple Coanda effect attachment on the end of the tube. The targets are heated indirectly with a high resistance heater element. Target temperatures up to 750 °C were attained. The observed erosion characteristics are consistent with previous work. For stainless steel, the erosion rate increases with increasing temperature above 400 °C. For aluminium the erosion rate reaches a maximum value at approximately 300 °C.     

Effect of composition and microstructure on slurry abrasion response of hardfaced martensitic stainless steel

Hardfaced martensitic stainless steel alloy was deposited on mild steel substrate by flux cored arc welding method. The slurry abrasion studies of weld-deposited hardfaced steel were performed using slurry abrasion test rig with 250–300 μm silica sand particles. The effect of weld compositional gradation on the abrasive wear resistance of hardfaced stainless steel at a distance of 0.6, 1.2, 2.4, 3.0 and 3.6 mm from the top surface was studied. The observed abrasion rates were rationalized in terms of mass loss, hardness and distance from the top surface i.e. diluted surfaces beneath the top surface. The abrasive wear mass loss increased with increasing distance beneath the top surface, which was attributed to the coarsening and morphology change in martensite phase. The results of the present work indicated change in morphology of martensite with increase in the distance beneath the top surface. The operating abrasive wear mechanisms involved ploughing, microcutting and indentation.     

Ball-cratering abrasion tests of high-Cr white cast irons

The application of a ball-cratering method to test three-body abrasive wear of bulk materials in the presence of large abrasive particles has been investigated. Three high-Cr white cast irons (WCIs) with different material properties were used as wear samples. Abrasive slurries contained two types of abrasive particles, silica sand and crushed quartz. Silica sand and crushed quartz particles have similar chemical composition and hardness but differ in sharpness. Wear rates of WCI samples were determined and the worn surfaces were examined by optical microscopy, SEM and Talysurf profilometry.It was found that the ball-cratering test can differentiate between the wear resistances of materials with similar properties. The wear resistance of WCIs in the presence of silica sand increased with increasing the hardness of the wear sample and decreasing the size of carbides in the microstructure. Smaller silica sand particles caused less wear damage than larger silica sand particles, even though the smaller particles were slightly sharper than the larger ones. When silica sand and quartz particles of the same size were used, the angular quartz particles caused much higher wear than the rounded silica sand particles. Surface morphologies of the wear craters on the WCI samples were examined in an SEM and then compared with the morphologies of the worn surfaces from slurry pumps. It was found that the silica sand particles generated surface morphologies similar to those found in the worn slurry pumps. In these surfaces the matrix was preferentially worn out and hard carbides were protruding. Wear surface morphologies produced by the angular quartz particles were different. They consisted of numerous superimposed indents and the microstructure phases were not distinguishable. This indicates that the type of abrasive particles used in ball-cratering testing significantly affects the test outcomes in terms of wear rates and wear surface morphology.     

Erosion of aluminium-based claddings on steel by sand in water

This paper describes the slurry erosion of a range of HVOF deposited aluminium-based claddings on steel by sand in water. Coatings, approximately 300 μm thick, of commercially pure aluminium, eutectic aluminium/silicon alloy (12%) and of a novel composite incorporating alumina in this alloy have been tested, both as sprayed and as ground to remove surface roughness as far as possible. Angular silica sand of mean diameter 235 μm was used at a concentration of 2.5% in tapwater at impingement angles of 90° and 30° and a jet velocity of 27 m/s. Mass loss data and surface structure, as shown by electron microscopy and profilometry, are related to the test conditions, initial surface topography, material hardness and microstructure, especially porosity. They are discussed in terms of the mechanisms of erosion that occur in the different materials, with reference to microcutting and plastic deformation of the surface and to the effects of the alumina inclusions. The consequences of poor flow-out, leading to significant residual porosity of the composite cladding are discussed.     

Slurry wear behavior of zinc-based alloys: influence of some material and test parameters

This investigation pertains to the analysis of slurry wear behavior of a zinc-based alloy. The effects of material composition/microstructure, slurry composition and traversal distance and speed on the response of the alloy system have been studied. Sample rotation method was adopted for testing the samples. In some cases, unexpected wear response (from conventional understanding) was observed. For example, presence of a less corroding phase like Si particles in the alloy system caused inferior wear response while increasing traversal speed led to improved wear behavior (in the liquid-only medium). Further, hard sand particles suspended in the test environment offered superior wear characteristics despite their additional erosive and abrasive damage to the samples. In the tested range (20–60 wt%) of sand concentrations in the slurry medium, the wear rate increased initially with increasing sand concentration, attained the maximum (although less than the liquid-only medium) at 40% sand and then finally followed a reversal in the trend at a still higher sand concentration of 60%. Increasing traversal speed from 4.71 to 7.02 m/s led to inferior response while the silicon containing alloy performed better than the one without the element in general in liquid plus sand slurries. The wear rate increased with traversal distance initially, attained the maximum and then decreased once again at still larger distances. The sensitivity of the rate of increase/decrease in wear rate with distance became less in the presence of suspended sand particles in the medium (electrolyte). The observed wear response of the samples has been substantiated through specific characteristics of affected surfaces. The latter also helped to understand the operating material removal mechanisms.     

Control and evaluation of particle impact conditions in a sand erosion test facility

For the prediction of actual damage to plant component materials and for making the erosion mechanisms clear, it is important to control and to evaluate the particle impact conditions in a testing facility. A sand blast type erosion test rig, which can achieve the particle impact velocities up to 135 m s⁻¹ and a wide range of impact angles has been constructed. The key factors in particle impact conditions of particle flux, impact velocity and impact angle were examined. The relative distance between particles and particle size was discussed, as the particle flux affected erosion rate of material. A new method was proposed to determine particle velocities in this facility. The theoretical velocity of the particle calculated by the equations of particle motion was compared with the experimental results. The divergence of particles from a geometrical angle was evaluated by measuring surface roughness of the specimens. Although some spread of the particles were observed surrounding the central damage area of the specimen surface, the greatest amount of damage was concentrated in the center. As a result, it was found that particle impact conditions were well controlled in this testing unit.     

Effect of Volume Fraction of Primary Alpha Phase on Solid Particle Erosion Behavior of Ti-6Al-4V Alloy

The present article evaluates the influence of independent control factors such as percentage of primary alpha phase, impact velocity, impingement angle, and erodent size on solid particle erosion behavior of Ti-6Al-4V alloy using a statistical approach. Microstructural variation in terms of different percentage of primary alpha phase of investigated alloy has been introduced by solution annealing it at different temperatures followed by thermal aging. Solid particle erosion tests have been carried out using a sand blast–type test rig following an experimental schedule based on Taguchi's orthogonal arrays. It is observed that erosion rate and the value of percentage elongation decreased with an increase in the content of primary alpha phase from 10 to 20% and then increased for the value corresponding to the content of 30% primary alpha phase in this alloy. We observed that the solid particle erosion behavior of the investigated alloy consisting of various percentages of primary alpha phase is related to their ductility. Among all four control factors, impact velocity of the erodent has been found to be the most significant control factor influencing the solid particle erosion behavior of this alloy followed by impingement angle, percentage of primary alpha phase, and erodent size. Impact velocity has greatest static influence of 91.35%, impingement angle has an influence of 4.69%, percentage of primary alpha phase has an influence of 2.28%, and erodent size has an influence of 0.42% on solid particle erosion having R² = 0.99. Material loss during solid particle erosion of this alloy was found to be ductile in nature. Ploughing or pile-up leading to platelet formation is the primary mechanism of material loss during erosion of the alloy.     

Assessment of the erosion resistance of steels used for slurry handling and transport in mineral processing applications

The wear environment of steels used for containing, transporting and processing erosive mineral slurries is often such that fluid borne particles form a layer moving at high speed across the wearing surface. Information on the performance ranking of such materials is limited, particularly with respect to the influence of steel hardness and microstructure on the resistance to erosion. This is particularly important for the oil sands industry of Northern Alberta where handling and processing of essentially silica-based solids results in extremely severe wear conditions. This paper presents slurry erosion data obtained on 11 commercially available wear resistant plate and pipeline steels with hardness values up to 750 HV. These data were obtained using a Coriolis erosion tester operated at 5000 rpm with an aqueous slurry containing 10 wt.% of 200–300 μm silica sand particles.

The Coriolis erosion tester was selected because it provides a low-angle scouring action that simulates the erosive conditions encountered in oil sands and tailings pipeline transport and in some related processing operations. Results show that this test method is able to discriminate clearly between the erosion resistance of these steels, expressed in terms of specific energy (the energy necessary to remove unit volume of test material), with the most erosion resistant steel being more than five times superior to the least resistant. A graphical relation between steel hardness and erosion resistance is given. A comparison is also made between slurry erosion data and the performance of the materials in the ASTM G65 dry sand rubber wheel (DSRW) sliding abrasion test. Comments on the influence of the macro- and microstructures of the steels on their wear behaviour are included.     

Effect of test parameters on large particle high speed slurry erosion testing

Abstract

A high speed slurry-pot wear tester was developed for close-to-reality heavy-duty wear testing of materials used in mineral applications. The samples are attached on four levels in a pin mill configuration. The tester and the developed sample rotation test method deliver reproducible results. This study focuses on the effects of testing parameters in large particle slurry testing. Parameters such as the speed, particle size and slurry concentration were varied. The effect of test duration was also examined. Round steel samples and slurry of water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for particle size, up to 23 wt-% for concentration and up to 20 m s^?1 for the sample tip speed. The relationships between the parameters are discussed. The kinetic energy of the large abrasive particles is also considered. Wear surfaces studied with optical and electron microscopy are also presented and discussed.     

砂粒粒径对航空涡轴发动机压气机叶片冲蚀磨损的影响研究

高原、沙漠和沿海等服役环境中不同粒径的砂粒不可避免地对涡轴发动机压气机叶片造成冲蚀磨损,破坏叶片叶型和动力学特性,严重危及涡轴发动机使用寿命和直升机飞行安全。基于Finnie冲蚀磨损理论推导了颗粒对金属表面的磨损率表达式,分析颗粒粒径对材料冲蚀磨损率的影响,以某型涡轴发动机压气机动叶和静叶为研究对象,设计搭建砂粒冲击速度测试装置和钛合金冲蚀磨损实验装置,通过典型砂粒粒径下冲蚀磨损实验获取磨损率表达式中与靶材材料和冲击速度相关的关键参数,结合气固两相流动力学分析开展砂粒粒径对压气机动叶和静叶冲蚀磨损的影响研究。结果表明：砂粒粒径与冲击速度存在内在关联,材料冲蚀磨损率与砂粒冲击速度呈幂函数关系。实验条件下,砂粒粒径由177 μm增至423 μm时,其冲击速度平均降低约17%。压气机动叶和静叶的磨损集中区域不随砂粒粒径的改变而变化,但磨损程度差异明显,其中177 μm砂粒对动叶和静叶造成的最大冲蚀磨损率浓度值相比423μm砂粒分别增加91%和131%。研究结果为涡轴发动机压气机叶片抗磨损设计提供了理论参考。     

Slurry Erosion Mechanism of Hydroturbine Steel: Effect of Operating Parameters

Performance of hydropower plant is severely affected by the presence of sand particles in river water. Degree of degradation significantly depends on the level of operating parameters (velocity, impingement angle, concentration, particle size and shape), which is further related to erosion mechanism. In this investigation, the effect of some of these operating parameters on erosion mechanism of generally used hydroturbine steel, CA6NM (13Cr4Ni), is reported. Morphology and variation in the martensite and austenite phases of the eroded surfaces were investigated using SEM and XRD. It was observed that velocity and impingement angle affect the erosion mechanism of CA6NM steel. Erosion mechanism was also significantly affected by the radial distance from the impact zone. Primary mechanism responsible for the removal of material at normal impingement angle was the formation and removal of platelets. At acute impingement angle, ploughing was observed to be one of the prime mechanisms responsible for the loss of the material. Other than these two well-known erosion mechanisms, the presence of another two erosion mechanisms was also observed. Models have been proposed for these unfamiliar erosion mechanisms. Interaction amongst different operating parameters was studied using line and contour plots. It was observed that the interaction between velocity and concentration was most significant. Using the experimental results, a statistical model based on regression approach was developed. Validity of this statistical model was checked using the experimental results from the literature and present study.