黄河砂冲击下水轮机用钢冲蚀攻角效应

研究了黄河砂冲击下水轮机有20SiMn钢和0CrNi5Mo钢冲蚀攻角效应。结果表明：冲蚀分为孕育期、增加期和稳定期三个过程；低攻角“增重”小于大攻角；攻角增加，冲蚀率增大。水轮机用钢冲蚀攻角效应奇异性与黄河砂冲击下“变形冲蚀”、“切削”和“二次冲蚀”的相对作用大小有关。     

High-temperature erosion tests on materials for fluidized bed combustor heat-exchanger tubes

In order to simulate and predict the erosion damage suffered by in-bed tubes in fluidised bed combustors, dedicated test equipment was set up at CISE's tribology laboratory with ENEL S. p. A (Italian National Electricity Board) support. This erosion rig was used to test and characterise the behaviour of AISI 310, P9, and P22 steels, candidate materials for this type of heat-exchanger tube. Tests were carried out at room temperature to characterise the erosion behaviour of these materials and at higher specimen (350°C and 500°C) and air (840°C) temperatures to simulate and characterise their behaviour in service. From this experimental work it turned out that, while at room temperature, the erosion behaviour of the three materials did not differ significantly, at high temperature P9 showed the best resistance in both test conditions and AISI 310 displayed an optimum behaviour at normal impact angles, but had the higher erosion rate at 30° impact angle.     

Nonlinear cavitation erosion of stainless steel in mercury versus applied power

The cavitation erosion rate for 316 stainless steel in mercury was found to increase in a nonlinear fashion with the maximum applied power. In addition, the incremental increase in erosion was observed to decrease with increased power in water, yet increased six to seven times when mercury was used as the cavitating fluid. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Introduction to the microscopy of erosion

Erosion of materials by the impact of small solid particles, by the impact of liquid drops and by cavitation in a liquid is discussed. Erosion arising from these three sources is described, terminology is defined, and the methods available for erosion testing in the laboratory are reviewed. A brief discussion is presented of the microscopical techniques which have been used to study erosion, and some of their advantages and drawbacks are outlined.     

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.     

Numerical simulation of the tube erosion resulted from particle impacts

In this paper, tube erosion caused by the turbulent flow of a dilute particle-laden gas is studied numerically. The particle impact and rebound model and the erosion model of ductile alloys obtained by Tabakoff et al. are used to predict the particle rebound phenomena and the erosion suffered by the tubes. The results obtained in this study include the distributions of particle collision frequency and erosion of tube surface.     

Variations in wear loss with respect to load and sliding speed under dry sand/rubber-wheel abrasion condition: a modeling study

The dry sand/rubber-wheel abrasion tester is widely used to evaluate the low-stress abrasion resistance of materials for the mining/mineral processing industry particularly for the oil sand mining industry. Since wear loss is usually proportional to the applied load, this test is often performed under a fixed load at a fixed sliding speed to rank materials. However, inaccurate or misleading information might be generated under an inadequate load. It has been observed that D2 tool steel exhibits very different responses to variations in the applied load. Above a certain load level, further increase in the applied load may lead to a decrease in wear loss of D2 steel. In order to understand this phenomenon, computer simulation was performed to investigate wear responses of several engineering materials, including D2 tool steel, stainless steel, Al 6061 and Cu 110, to variations in applied load under the dry sand/rubber-wheel abrasion condition. It was demonstrated that the decrease in wear loss of D2 tool steel with an increase in the applied load was attributed to failure of the abrasive sand. Wear losses of the materials with respect to the sliding speed were also investigated. The prediction from the simulation was compared to experimental observations.     

氮气气源的干燥方法及其应用

对吸附式气源干燥方法的类型和特点作了分析介绍,并在探讨其应用的基础上,重点介绍了氮气干燥气源的组成、应用背景、工作原理、工作流程和特点,简要分析了用氮气干燥气源对密闭容器进行干燥处理和气密性检测的方法和优点。     

Tribological investigation of commercially sintered steels under dry sliding conditions against austenitic steel

In this study the wear and friction of uncoated sintered steels, their relationship with microstructure and toughness when tested against austenitic steel were investigated. The metallographic investigation and the quantitative testing are interrelated in such a way that one can explain the other, and together they explain the wear behaviour of the sintered parts. The paper identifies the main wear mechanisms in this particular type of testing for the investigated materials. For the same materials, the paper also proves in quantitative terms (for the first time) the correlation between material fracture toughness and its wear behaviour - a correlation demonstrated before for other materials by theoretical studies.     

泵用干气密封技术及其应用进展

干气密封技术在离心式压缩机等高速流体机械上获得了广泛应用,在泵、反应釜等低转速设备上的应用开始引起重视.综述了国内外泵用干气密封技术及其应用现状,介绍了泵用干气密封的技术特点,包括结构形式、布置方式、端面槽型等,并介绍了成功应用于石化行业的典型案例.同时介绍了主要密封公司典型泵用干气密封产品的技术特点.     

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.     

Characterizing cavitation erosion particles by analysis of SEM images

Wear particles produced by vibratory cavitation erosion on stationary-aluminum Al-99.999 were analyzed using scanning electron microscope (SEM), forming a database for further analysis. The particle morphology features were first clarified based on the characteristic stages of the vibratory erosion rate-time pattern. Next, size, area, perimeter and shape factors (elongation and roundness) were determined for eroded particles, using image analysis software. In incubation period, the particles have distinctive characteristics which differed from that for the subsequent periods. These characteristics include the value of longitudinal ratio and roundness factor, limit size range and morphological features such as lamella shape, folding, curving with one of the particle surfaces as the virgin surface. In acceleration, steady-state and attenuation periods, the particles have a wide size range and larger thickness compared with that for the incubation period. The maximum particle size reached about 360 μm in acceleration and steady-state period. For all the cavitation erosion rate periods, the particles were out of sphericity and they have a roundness factor larger than 2. Detailed surface characteristics of the particles produced during cavitation erosion is significant and can open ways for monitoring the cavitation erosion progress.     

气体端面密封试验台的测试系统

介绍一种基于虚拟仪器技术的气体端面密封试验台的测试系统。简要说明实验台的构成和测试系统硬件的组成：重点分析了各个参数的测试方法。同时展示了虚拟仪器开发平台的主要功能和特点。     

干气密封在离心泵上的应用

P-6201脱丁烷塔顶回流泵是中压加氢装置的关键设备,泵腔介质为轻烃,其中含有30%的硫化氢。硫化氢属于强烈的神经毒素,易燃、易爆,一旦大量泄漏到环境中,将带来极大的安全隐患。由于介质中硫化氢含量较高,在使用及检修拆泵时容易造成环境污染以及对操作人员造成伤害。P-6201采用的是单端接触式机械密封,使用寿命短。随着环保意识不断加强,对炼油装置的安全及可靠性要求越来越高。公司基于环保、安全、寿命等原因考虑,必须对这类高危泵进行改造。     

The cavitation erosion damage process of dynamically loaded journal bearings

The cavitation damage model was built using finite element analysis software MSC.Marc. This paper attempted to numerically analyze the action process based on damage mechanics when a jet created by bubble collapse acted on the bearing surface in the process of cavitation erosion. The numerical results show that the values of equivalent plastic strain and void volume fraction increase with time. The values of damage scalar are higher on the bearing surface and subsurface, and decrease when it approaches the interface of overlay and nickel layer. The strain history and damage evolvement of bearing material acted on by jet impact load can be calculated efficiently using the proposed method, which develops a new method of analyzing cavitation erosion failure of the bearing surface. __________ Translated from Journal of Shanghai Jiaotong University, 2005, 39(7) (in Chinese)     

酯硬化水玻璃砂在阀门铸钢件生产中的应用

介绍了酯硬化水玻璃砂的工艺特性及配制条件。论述了在阀门铸钢件生产中，应用酯硬化水玻璃砂对提高产品质量和生产效率的重要作用。     

An investigation on the erosion resistance of rare earths nitrocarburized 40 Cr steel

The effect of rare earths (RE) on erosion resistance of nitrocarburized 40 Cr steel is investigated. Results indicate that a significant improvement occurs in erosion resistance of nitrocarburized 40 Cr steel by introducing RE in nitrocarburizing processes comparing conventional nitrocarburizing processes. Measurement of mechanical properties exhibits that both hardness and toughness of nitrocarburized 40 Cr steel increase in the case using RE nitrocarburizing processes comparing the conventional. Metallurgical microscopy reveals that there is an improvement in the nitrocarburizing layer microstructure attributed to an introduction of RE in nitrocarburizing, which results in an improvement in erosion resistance and mechanical properties. Surface morphology observation of tested samples reveals that predominantly furrow-like peeling from plastic deformation are observed in RE nitrocarburizied 40 Cr steel, while the furrow-like peeling with initial cross crack and large grinding peelings takes place in conventionally nitrocarburized samples.     

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.     

Analysis of boiler-tube erosion by the technique of acoustic emission Part I. Mechanical erosion

This paper investigates the mechanical erosion of the metal tubes in bagasse-fired boilers with the aid of the acoustic emission technique. By studying the material removal under various collision conditions, the paper analyzes the dependence of the erosion wear upon the impact angle, velocity, size and concentration of the particles. It was found that the material removal mechanisms were mainly dependent on the particle collision angle and fell into four regimes characterized by rubbing and scratching, cutting and cracking, forging and extrusion as well as sputtering and adhesion. The highest wear rate took place with the cutting and cracking mechanism when the particle collision angle was in the range of 20–30°. The variation of the acoustic emission energy confirmed the conclusions. Finally, three simple formulae were developed to show the dependence of the erosion wear upon the main erosion parameters.