Evaluation of oxy-acetylene flame angle effect on the erosion resistance of SiC/ZrB2–SiC/ZrB2 multilayer coatings fabricated by the shielding shrouded plasma spray technique

In the present study, the effect of oxy-acetylene flame angle on the erosion resistance of SiC/ZrB₂–SiC/ZrB₂ multilayer coatings with the gradient structure was investigated. To this aim, first, the SiC inner layer was applied by the reactive melt infiltration (RMI) technique; then ZrB₂ and ZrB₂–SiC layers with 10, 20 and 30%wt. SiC were applied on graphite by the plasma spraying technique. To prevent the oxidation of ZrB₂ and SiC particles, the plasma spraying process was performed by a solid protective shield. To evaluate the performance of the coatings in erosive environments, the samples were exposed to oxy-acetylene flame at the angles of 30°, 60° and 90° for 360 s; the destruction mechanism of SiC/ZrB₂–SiC/ZrB₂ multilayer coatings appeared to be controlled mechanically and chemically. The results of the erosion test showed that at the low flame angles of about 30°, due to the shear forces of oxy-acetylene flame, mechanical erosion overcame the chemical one. With increasing the flame angle, due to raising the surface temperature, chemical erosion overcame the mechanical one; so, most chemical destruction occurred at the flame angle of 90°. Also, the results of the erosion test showed that the total chemical and mechanical destruction at the angle of 60° was greater than that in other angles. Also, among the coatings tested, SiC/ZrB₂- 20% wt. SiC/ZrB₂ coatings had the best erosion resistance; so, the weight changes under the oxy-acetylene flame at the angles of 30° and 60°, respectively, were about ?0.038%. and ?0.355%; meanwhile, at the angle of 90°, it was about +4.3%.     

碱金属和锌对高炉用SiAlON结合刚玉砖的复合侵蚀

将高炉用SiAlON结合刚玉砖制成外部尺寸为50mm×50mm,内孔尺寸为25mm×25mm的坩埚,分别加入由Na2CO3、K2CO3、ZnO和宝钢高炉现场高炉灰配制的炉渣(其w(Na2O+K2O)=2.75%,w(ZnO)=5.1%)和用K2CO3、ZnO、石墨配制的炉渣(其w(Na2O+K2O)=25%,w(ZnO)=25%),然后分别在还原气氛下于1350℃16h和1100℃40h进行侵蚀试验。将侵蚀后的试样纵向对称剖开,观察渣对试样的侵蚀和渗透情况,进行SEM和EDAX分析。结果表明:碱金属和锌含量不同的两种炉渣对SiAlON结合刚玉砖的侵蚀速度都很小;碱金属侵蚀机理主要是SiAlON与碱蒸气反应生成钾霞石,与渣反应生成铁橄榄石,并参与硅酸盐玻璃相的生成;刚玉颗粒与渣中的FeO、Na2O和K2O反应生成铁铝尖晶石和少量针状β-Al2O3;锌对该砖没有产生明显的化学侵蚀。     

铝合金腐蚀声发射信号特性研究

采用声发射检测技术对5A03(LF3)铝合金腐蚀过程进行监测,证明利用声发射技术检测铝合金贮罐腐蚀破坏状态的可行性。根据实际使用中铝合金贮罐发生腐蚀的机理及特性制定5A03铝合金腐蚀的模拟试验方案,采集并分析了铝合金腐蚀声发射信号的分布及关联性。最后结合电化学试验验证了本实验的合理性。文章结论可作为现场声发射诊断的初步依据。     

Fracture in CVD diamond

The fracture behaviour of thick, textured films of chemical-vapour-deposited diamond is discussed with particular emphasis on the influences asserted by the polycrystalline microstructure. Cracking is investigated on two different scales, firstly where it is large in that it traverses many grains and pertains to the fracture of the bulk. The second is where the fractures are localised, resulting from repeated small particle impacts and the mechanisms of material removal at the grain-size-scale are elucidated. The behaviour at this smaller level can be rationalised in terms intermediate to bulk fracture and that observed in single crystal diamond. The effects of grain size, grain boundaries, crystallographic orientation, twinning, internal stresses and pre-existing flaws are discussed. A new value for the fracture toughness is calculated and the gravimetric erosion rate for different surface orientations measured.     

水轮机用碳钢材料的抗冲蚀磨损性能研究

通过对水轮机用 5 5 # 碳钢和 1Cr18Ni9Ti不锈钢在不同冲蚀速度、不同浆料含沙量及不同冲蚀角度条件下的冲蚀磨损试验 ,探索了材料的冲蚀失效规律及微观破坏机制。结果表明 ,材料的冲蚀磨损失重率随冲蚀速度、浆料含沙量的增加而增加 ,且 1Cr18Ni9Ti的抗冲蚀性能优于 5 5 # 钢 ;冲蚀角度对材料的冲蚀性能影响最为显著 ,在 0°～ 45°时冲蚀失重率随着冲蚀角度的增大而增大 ,45°时出现极大值 ,45°～ 60°时材料冲蚀失重率随着冲蚀角度的增加而减小 ;腐蚀对材料冲蚀性能的影响不容忽视     

风力机叶片涂层冲蚀磨损实验装置的设计

风力发电机叶片在风沙环境中运行时会受到挟沙风的冲蚀,导致叶片表面涂层损毁并且降低叶片使用寿命,同时也增加叶片的维护成本。为了探究风力机叶片受挟沙风冲蚀磨损情况,研制一种涂层冲蚀磨损实验装置,该实验装置以压缩空气为动力,通过压缩空气气管接通气源。压缩空气在冲蚀管中建立工作压力,在冲蚀管内完成沙料和压缩空气充分混合,形成高速运动的挟沙风;再利用PLC控制步进电动机转速,通过螺旋推进器进行输沙率控制,由冲蚀管喷嘴喷出,喷射到风力机叶片模型表面对其进行冲蚀磨损实验。该冲蚀装置可实现多种冲击风速、携沙量、冲击角度的多工况磨损实验,能够提供较为精确的实验数据。     

在役油罐内壁除锈喷嘴外流场数值模拟

针对在役单层油罐改造成双层罐的除锈问题,选用磨料水射流喷嘴为研究对象,使用计算流体力学方法,进行了混合磨料水射流对油罐内壁除锈效果的数值模拟。以射流打击靶面的最大剪切力和冲蚀磨损率作为评价指标,研究结果表明:前混合磨料水射流达到相同的除锈效果相较于后混合磨料水射流所需的射流压力更低,射流入射压力为20 MPa时,除锈效果较理想且具有较好的经济性;剪切力在靶面上存在一个核心作用区,最大剪切力位置不在靶面中心处;冲蚀磨损率随磨料的体积浓度、磨料粒径、磨料密度的增大而增大,而最大壁面剪切力不随其增大而变化。     

Assessment of Sediment and Pollutants in Buyo Lake,Ivory Coast,Using SWAT （Soil and Water Assessment Tool） Model

The changes in land use in the last 30 years in the territory of agro-forest watershed of Lake Buyo resulted in significant sediment into the lake. Sediments are a preferred means of transportation for certain pollutants, like phosphorus in excess. By mapping the source areas of erosion, the authors can determine the risk areas and help to prioritize interventions in the territory. This mapping is done using the SWAT （soil and water assessment tool） model. Several types of data, including topography, land use, soil and climate data are needed to run the model. In this paper, all different steps are presented, from the designing of HRU （hydrological response units）, basic units to run the SWAT model until the simulations. The establishment of HRU has three main stages： space discretization, land use and soil data integration and HRU distribution： （1） space discretization which consist in extracting the limits and the water network of the watershed from the DEM （digital elevation model） and in subdividing them into sub-basins; （2） land use and soil data integration： it consists in digitizing the physical maps of land use and of soils under Mapinfo 7.5 and in keeping them in ＂shape＂ format; （3） HRU distribution： it leads to subdivide the sub-watersheds in small units that combine a single soil type and one type of land use. It appears from this study to obtain 23 sub-watersheds and 71 HRU. Once the HRU designed, it is necessary to integrate climate data, data on physico-chemical characteristics of soils and agricultural practices, before starting the simulations. This will allow the model to assess the risk of sedimentation and eutrophication of the lake using the MUSLE （modified universal soil loss equation） and phosphorus cycle.     

柴达木盆地北缘中生界剥蚀厚度恢复

认为地层剥蚀厚度能否根据压实规律来恢复,其决定因素并非是新沉积层厚度是否大于剥蚀厚度;当不整合面以上新沉积层对不整合面以下老地层施加的压力大于被剥蚀地层(剥蚀前)对不整合面以下老地层施加的压力时,不整合面以下老地层的压实规律被破坏,无法用声波时差法恢复剥蚀厚度,否则可以恢复。据此,以用声波测井资料恢复的地层剥蚀厚度为依据,结合未被剥蚀地层厚度趋势延伸法、盆地构造演化分析法,对柴达木盆地北缘中生界剥蚀厚度进行了恢复,认为柴达木盆地北缘剥蚀量从西向东增大,昆特依坳陷和冷湖构造带的剥蚀量(约500m)大于其东部南八仙、鱼卡等地区(约100m),潜西—冷湖四号地区剥蚀量最大(最大可超过1400m)。图5参4(梁大新摘)     

基于气-固双向耦合的输气管道最大冲蚀角度预测

弯管作为气田集输管道输送系统中的常用组件,极易受到固体颗粒对管壁的冲蚀破坏。为了研究输气管道的冲蚀规律、 预测弯管最大冲蚀位置,采用Eulerian-Lagrangian 方法计算了管内气、固两相的流动情况,在Eulerian 坐标系下求解气体连续相 流场,在Lagrangian 坐标系下求解颗粒离散相运动轨迹,利用Erosion/Corrosion Research Center（E/CRC）冲蚀模型以及Grant 和 Tabakoff 颗粒-壁面碰撞模型计算管壁冲蚀速率。数值计算过程中考虑了气、固两相之间的双向耦合作用,利用多种模型研究了在 不同弯径比及颗粒直径影响下的弯管冲蚀规律、颗粒运动轨迹及弯管最大冲蚀角度,并提出最大冲蚀位置预测方程。研究结果表明： ①固体颗粒对弯管的冲蚀存在着临界直径,在颗粒临界直径前后的冲蚀规律明显不同;②固体颗粒直接碰撞和滑动碰撞共同作用导 致弯管出现不同的冲蚀形貌,并影响最大冲蚀速率的出现位置;③根据临界颗粒直径以及管道中颗粒运动轨迹提出的冲蚀最严重位 置预测方程能很好地预测弯头处最大冲蚀角度,可以为输气管道冲蚀预测提供参考。