STUDY ON THE MECHANISMS OF EROSION OF METALS AT LOW IMPACT ANGLE

The mechanisms of solid particle erosion of several pure metals and steels at low impact angle were studied comprehensively by SEM observations of the worn surface,wear debris analysis, subsurface hardness measurements,incremental erosion tests and sequential erosion study techniques. It was found that at the beginning of erosion,craters and lips were formed on the surfaces of ductile metals due to the deformation caused by the impacting of the particles. The deformed lips were then forged back and forth again and again in erosion process. As a result , small chips of deformed lips were stripped off continuously in the process. All of the evidences show that the erosion mechanisms are encompassed mainly by the process of plastic deformation,lip formation and spelling with ductile metals,while microcutting is more easy to occur with hardened steels.

Road Lateral Disconnection and Crossing Impacts in River Landscape of Lancang River Valley in Yunnan Province,China

Roads are conspicuous components in a river landscape;however,their impacts on river landscape patterns and ecological processes have not been systematically studied at the watershed scale.In this paper,the Lancang River Valley in Yunnan Province,China was selected as a case to study road lateral disconnection and crossing impacts and identify river-road network interaction.This study was primarily focused on the road impacts on soil erosion intensity and patch density by using GIS analysis at different scales and explored their distribution with terrain factors.The results showed that river density revealed spatial autocorrelation although both of the roads and rivers were distributed unevenly in the valley.The lateral road(road curvature≥1.1)proportion correlated with soil erosion intensity(p 0.01)at the small sub-basin scale.Soil erosion intensity decreased with increasing lateral road buffer width.Light erosion generally accounted for a large proportion of the erosion in the lateral road buffer zones(1.0–4.0 km),while higher class lateral roads imposed greater impacts on soil erosion than lower class roads,which primarily had a moderate erosion level.In addition,the results of road-river intersection density indicated that road crossing impacts were significantly correlated with patch density at the small sub-basin scale.Topography factor(percent of slope>25°in each sub-basin had a close relationship with the ratio of total length of road line with curvature value≥1.1 to the total number of intersections.The correlation(p 0.01)between road impacts and terrain factor revealed that topography affected the road impact distribution in the Lancang River Valley.

Erosion Resistance of CaO-Al_2O_3-SiO_2 System Glass-Ceramics

The erosion resistance tests were used to research the erosion wear behavior of CaO-Al-2O-3-SiO-2 system glass-ceramic. With the orthogonal test method, the factors that affect the erosion wear of CaO-Al-2O-3-SiO-2 system glass-ceramic such as particles property, impact angle, impact time, size of particles were discussed.The results show that erosion rate rises along a straight line at the early period of erosion wear.With the impact time increased,the erosion rate deviates from original staight line,tendency of the erosion rate increases.With the size of paricle increased,it will have more kinetic energy,the erosion rate of the surface of glass-ceramics ploate rises.

HVOF喷涂WC/Co涂层冲蚀磨损机理研究

采用超音速火焰喷涂工艺(HVOF)制备WC-12Co喷涂层,采用棕刚玉磨粒对所制备涂层在冲蚀角度分别为30°和90°下进行常温固体粒子冲蚀磨损试验。探讨了WC-12Co涂层的冲蚀磨损机理,结果表明:WC-12Co涂层为典型的脆性材料。

配气站浮动式球阀阀芯迎流面冲蚀行为及其后果

为了避免配气站常用浮动式球阀因高运行负荷与气携粉尘持续冲蚀而突发安全事故,选用Ahlert冲蚀速率模型,模拟分析了当30°开度时304不锈钢阀芯迎流面的冲击角变化趋势,科学评估了阀芯迎流面的冲蚀行为与薄弱区域。结果表明,粉尘在阀芯迎流面A~I测点处的冲击角随壁厚损失呈同步增大趋势,迎流面受粉尘持续冲蚀而不断凹陷,致使迎流面上粉尘的流速从7.4 m/s降至5.9 m/s;迎流面冲蚀后表面粉尘流速也呈现减小趋势,从0.010 kg/s降低至0.005 kg/s,且颗粒沉积的区域也在向球体的后方移动;迎流面上各处壁厚减薄速率不一,应有针对性地布置球阀防冲蚀涂层,并采用动态方法核算球阀在节流工况下的使用寿命。研究结论可为配气站用球阀的设计和维护提供参考。

Erosion behavior of a ship propeller material of QAl9-4 alloy

The erosion behavior of a QA19-4 alloy as a ship propeller material was investigated.The effects of the solution,the impact angles and the sand content were considered.The test results demonstrate that the mass loss of the alloy in 3.5 wt%NaCl solution is 1.35 times that in tap water,due to the corrosive effect of Cl^(-).The mass loss of the alloy increases as the impact angle increases up to~30°and consequently decreases as the impact angle increases.Also,this feature is typical for the ductile metal behavior.At the impact angle of 0°,this feature is associated with the predominant erosion mechanisms,such as shallow plowing and surface fatigue;at 30°,this feature is micro-cutting,deep plowing and surface fatigue;and at 45°,it becomes indentation accompanied by extruded lips.The mass loss and surface roughness of the alloy increase as the sand content increases under the testing conditions.

三维编织和角联锁复合材料的高速冲击响应

为了探究三维纺织结构复合材料高速冲击下应变率效应和结构效应,制备了碳纤维增强三维编织和三维角联锁复合材料,采用霍普金森压杆(SHPB)系统和高速摄影系统记录了三维编织和三维角联锁复合材料在高速冲击过程中应力应变曲线和渐进损伤过程。结果表明:编织和角联锁复合材料在高速冲击下都具有一定的应变率效应,并且都呈现剪切损伤,但编织复合材料呈现明显延性损伤而角联锁复合材料呈现明显脆性损伤。由于编织复合材料内部纤维束交织紧密,损伤后仍能承受一定载荷并且结构也能保持完整性,因此相较于三维角联锁复合材料,三维编织复合材料具有更好的抗冲击性能。

CT80连续油管液固两相流冲蚀磨损试验研究

针对国产CT80连续油管在服役过程中发生的冲蚀磨损问题,采用自制的室内喷射式冲蚀试验装置,与油套管用N80钢进行对比试验,研究了冲击角度、流速以及砂含量3种影响因素对冲蚀速率的影响。结果表明:CT80钢在冲击角度为30°时,冲蚀速率最大可达9.06×10^(-7)kg/kg,而N80钢在冲击角度为15°时冲蚀速率最大值为6.03×10^(-7)kg/kg。N80钢在流速从1 m/s增大到5 m/s时,最大冲蚀速率从4.56×10^(-8)kg/kg增加到6.03×10^(-7)kg/kg,增幅约为13.2倍,是增长速率最快的阶段。CT80钢在相同流速阶段增幅比N80钢小,约为10倍。N80钢在砂含量从0.5%增加到1%时,冲蚀速率增长最快,由5.28×10^(-7)kg/kg增长到6.1×10^(-7)kg/kg,而CT80钢在砂含量从0.5%增加到3%时,冲蚀速率呈现先增大再减小的波动趋势。该试验为油田复杂环境下完井管柱的选材提供了参考。

Analytical modeling of oxide thickness variation of metals under high temperature solid-particle erosion

The paper presents a study of model development for predicting the oxide thickness on metals under high temperature solid-particle erosion.The model is created based on the theory of solid-particle erosion that characterizes the erosion damage as deformation wear and cutting wear,incorporating the effect of the oxide scale on the eroded surface under high temperature erosion.Then the instantaneous oxide thickness is the result of the synergetic effect of erosion and oxidation.The developed model is applied on a Ni-based Al-containing(Ni–Al)alloy to investigate the oxide thickness variation with erosion duration of the alloy at high temperatures.The results show that the thickness of the oxide scale on the alloy surface increases with the exposure time and temperature when the surface is not attacked by particles.However,when particles impact on the alloy surface,the oxide thickness is reduced,although oxidation is continuing.This indicates that oxidation does not benefit the erosion resistance of this alloy at high temperatures due to the low growth rate of the oxide.

Modeling study of solid-particle erosion with consideration of particle velocity dependent model parameters

An advanced erosion model that correlates two model parameters—the energies required to remove unit mass of target material during cutting wear and deformation wear,respectively,with particle velocity,particle size and density,as well as target material properties,is proposed.This model is capable of predicting the erosion rates for a material under solid-particle impact over a specific range of particle velocity at the impingement angle between 0◦and 90◦,provided that the experimental data of erosion rate for the material at a particle velocity within this range and at impingement angles between 0◦and 90◦are available.The proposed model is applied on three distinct types of materials:aluminum,perspex and graphite,to investigate the dependence behavior of the model parameters on particle velocity for ductile and brittle materials.The predicted model parameters obtained from the model are validated by the experimental data of aluminum plate under Al2O3 particle impact.The significance and limitation of the model are discussed;possible improvements on the model are suggested.

30CrMo合金钢的冲蚀磨损性能研究

采用自制的喷射型冲蚀磨损试验机,研究在水力压裂工况下,高速携砂液对高压管汇材料30CrMo的冲蚀磨损作用,分析冲蚀磨损机制以及冲蚀角度和冲蚀速度对30CrMo合金钢冲蚀性能的影响。结果表明,30CrMo合金钢在高速粒子冲击下,其耐冲蚀磨损性能表现一般,属于典型的金属塑性材料;冲蚀角度为30°时,30CrMo的冲蚀磨损量最大;30CrMo的磨损机制与冲蚀角度有直接的关系,冲蚀角度小于30°时,冲蚀磨损机制以切削模型为主,大于30°时以局部塑性变形模型为主;冲蚀磨损量随冲击速度增加而显著增加,在高速冲击时,30CrMo钢的冲蚀磨损较为严重。

流体力学因素对冲刷腐蚀的影响机制

综述了流速流态、攻角以及颗粒性质等流体力学因素对冲刷腐蚀的影响机制， 讨论了流体力学因素的重要性、流体力学条件的描述、关键的流体力学参数以及扰流条件下局部流速流态的获取，并论述了如何从流体力学方面控制冲刷腐蚀．

冲蚀角度对40CrNi2Mo材料冲蚀磨损性能的影响

采用自主研发的冲蚀磨损试验机对40CrNi2Mo合金钢试样进行冲蚀磨损试验,讨论在不同冲蚀角度下40CrNi2Mo合金钢材料的冲蚀磨损机制,采用电镜分析材料冲蚀磨损后的形貌特征。结果表明:该合金钢的磨损量随冲蚀角度的增大先增大后减小,最后出现小幅回升,最大磨损量出现在30°左右,小角度冲蚀磨损特征表现为微切削,大角度冲蚀磨损特征表现为塑性变形,符合典型的塑性材料的冲蚀磨损规律。

一种旋转式液固两相流冲蚀磨损试验装置的研制

针对目前液固两相流冲蚀磨损试验装置存在实际冲角误差大、浆体浓度不均匀等问题,研制了一种旋转式冲蚀磨损试验装置。该装置允许的冲角范围为0°～90°,冲击速度为0～28.5m/s连续可调,利用搅拌叶片和导流槽实现不同冲击速度下浆体浓度的均匀性,具有速度稳定、可同时测试8个不同冲角下的试样、操作方便等特点。对低碳钢在不同冲击速度和冲角下的试验表明,所测得试验数据误差在6.8%以内,冲蚀磨损规律与经典结论一致。因此,该装置有望作为一种准确可靠的冲蚀磨损试验研究新平台而应用于耐冲蚀磨损优化设计和寿命预测等领域。

冲蚀角度和弯头几何尺寸对冲蚀磨损的影响研究

为了更深入研究输气管道中重点管件——弯头的气固两相流问题,弄清固体颗粒运动轨迹与冲蚀磨损之间的关系,根据相似性原理搭建了模拟试验平台。采用k-ε双方程模型建立相应的气固两相流仿真模型,并将仿真结果同试验结果进行对比,验证了仿真模拟的正确性。在此基础之上,详细进行了固体颗粒的入射角度和弯头的几何尺寸对冲蚀磨损的影响研究。结果表明,冲蚀的入射角度对弯头的冲蚀磨损情况有很大影响。当入射角偏向弯头内管壁时,最大冲蚀率随着入射角的增大而增大。当入射角偏向外侧管壁时,入射角为15°时弯头的最大冲蚀率最大。另外,通过改变弯头的曲率半径和外形,都可以减小弯头的最大冲蚀磨损速率。

超高速碰撞LY12铝靶产生闪光辐射的速度及角度效应

为了研究超高速碰撞产生闪光辐射的速度及角度效应,利用建立的瞬态光纤高温计测量系统结合二级轻气炮加载系统,进行了6种实验条件下的超高速碰撞实验。每组实验使用一组光纤探头,基于实验所获原始数据结合标定,通过Matlab编程处理得到了给定实验条件及光纤探头安装条件下,超高速碰撞LY12铝靶产生的闪光辐射与碰撞速度和弹丸入射角度的关系。实验结果表明,超高速碰撞LY12铝靶产生的闪光辐射在温度峰值出现前近似与碰撞速度和弹丸入射角度(弹道与靶板平面的夹角)正弦乘积的平方成正比;碰撞闪光辐射在温度峰值出现后近似与碰撞速度和弹丸入射角度正弦乘积的0.75次幂成正比,与理论推导结果基本吻合。

小口径PELE作用薄靶板影响因素的实验研究

为了确定影响小口径PELE对薄靶板作用效果的关键因素，改变弹体材料、装填物材料、弹丸着速和着角，在12．7mm弹道枪上发射PELE对固定靶板进行撞击试验。试验结果表明，弹体采用压拉比高的材料时，PELE横向效应明显；在试验速度范围内，随着速的提高，PELE破片数量增多，横向效应增强；装填物材料对横向效应的主要影响因素是泊松比和弹性模量，而不是密度；在0°～45°范围内，随着角的增大，PELE横向效应增强。这些结论为小口径PELE的设计和运用提供了重要依据。

泡沫镍/环氧树脂/碳化硅双连续复合材料的料浆冲蚀行为研究

设计并制备出一种颗粒增强型双连续三元复合材料--泡沫镍/环氧树脂/碳化硅双连续复合材料,以材料的总损失量为重点研究了其在含氯化钠料浆冲蚀条件下的损伤行为.结果表明:颗粒增强的泡沫镍/环氧树脂/碳化硅双连续三元复合材料的耐料浆冲蚀性能明显优于环氧树脂/碳化硅二元复合材料;不同孔径泡沫镍骨架的复合材料的冲蚀量随攻角变化出现了不同的峰值;合理匹配泡沫镍骨架的孔径和体密度,可制备出具有优异抗冲蚀性能的颗粒增强双连续复合材料.

陶瓷材料冲蚀磨损的研究

冲蚀磨损是现代工业生产中常见的一种磨损形式 ,陶瓷材料由于其所具有的一些固有特性而在冲蚀环境下的应用越来越广。本文探讨了影响陶瓷材料冲蚀行为的因素 ,讨论了环境参数 (如冲角、冲蚀速度、冲蚀时间和温度 )、磨粒性能 (如硬度、粒度和形状 )、靶材性能 (如硬度、断裂韧性和显微组织结构 )等对冲蚀的影响规律。