WC-M coating to improve resistance of hydraulic turbines to cavitation erosion and abrasion

WC M hard faced ceramic coating was made on the substrate of steel by means of high velocity oxygen fuel flame (HVOF) thermal spraying. The resistance of this coating to cavitation erosion and abrasion (CEA) is about 2.5 times higher than that of 188 stainless steel, and is about 1.5 times higher than that of Stellite alloy (CoCrWC) made in America. When this coating were applied to the hydraulic power stations with more silt content in the flow water, which reaches 50 kg/m 3, the resistance of above mentioned coating to CEA was about 2 times to that of NiCr alloy coating, and is about 45 times to that of OCr13Ni4Mo stainless steel. In addition, the micro hardness, microstructures and electron probe analyzing of the WC M coating are all discussed.

Research on Prediction Model for Erosion and Abrasion of Barrel Based on LSSVM

To predict the erosion and abrasion of high bore pressure tank gun barrel, the least square support vector machine (LSSVM) algorithm was used. Based on the gun firing test data, the prediction model for barrel's erosion and abrasion was established. It was adopted to predict the wear increment of gun barrel. The results show that the prediction values given by the model coincide with the measured data better, and the model can predict the barrel's wear accurately and rapidly.

A review on the erosion mechanisms in abrasive waterjet micromachining of brittle materials

The fabrication of miniature structures on components with high-integrity surface quality represents one of the cutting edge technologies in the 21st century.The materials used to construct such small structures are often difficult-to-machine.Many other readily available technologies either cannot realise necessary precision or are costly.Abrasive waterjet(AWJ)is a favourable technology for the machining of difficult-to-machine materials.However,this technology is generally aimed at large stock removal.A reduction in the scale of this technology is an attractive avenue for meeting the pressing need of industry in the production of damage-free micro features.This paper reviews some of the work that has been undertaken at UNSW Sydney about the development of such an AWJ technology,focusing on the system design currently employed to generate a micro abrasive jet,the erosion mechanisms associated with processing some typical brittle materials of both single-and two-phased.Processing models based on the findings are also presented.The review concludes on the viability of the technology and the prevailing trend in its development.

Structure of Micro-nano WC-10Co4Cr Coating and Cavitation Erosion Resistance in NaCl Solution

Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.

Chinese Standards on Refractories Refractory Products-Determination of Abrasion Resistance at Ambient Temperature GB/T 18301-2012

This standard specifies the terms and definitions, theory, apparatus, specimens, test procedures, calcu- lation results, apparatus check and test reports, etc. of abrasion resistance at ambient temperature of refractory products.

THE EROSIVE PROCESS IN ABRASIVE WATERJET CUTTING OF POLYMER MATRIX COMPOSITES

A study is carried out which analyzes the machinability of polymer matrix composites under an abrasive waterjet (AWJ) and the associated erosive process or mechanism. It shows that AWJ cutting can produce good quality kerf at high production rate if the cutting parameters are properly selected. A scanning electron microscopy (SEM) analysis of the cut surfaces reveals that the erosive process for the matrix material (resin) involves shearing and ploughing as well as intergranular cracking, while shearing is a dominant process for cutting the fibres in the upper cutting region but the fibers are mostly pulled out in the lower region.

Numerical analysis of hydroabrasion in a hydrocyclone

The velocity profiles and separation efficiency curves of a hydrocyclone were predicted by an Euler-Euler approach using a computational fluid dynamics tool ANSYS-CFX 14.5. The Euler-Euler approach is capable of considering the particle-particle interactions and is appropriate for highly laden liquid-solid mixtures. Pre- dicted results were compared and validated with experi- mental results and showed a considerably good agreement. An increase in the particle cut size with increasing solid concentration of the inlet mixture flow was observed and discussed. In addition to this, the erosion on hydrocyclone walls constructed from stainless steel 410, eroded by sand particles （mainly SiOz）, was predicted with the Euler-La- grange approach. In this approach, the abrasive solid particles were traced in a Lagrangian reference frame as discrete particles. The increases in the input flow velocity, solid concentration, and the particle size have increased the erosion at the upper part of the cylindrical body of the hydrocyclone, where the tangential inlet flow enters the hydrocyclone. The erosion density in the area between the cylindrical to conical body area, in comparison to other parts of the hydrocyclone, also increased considerably. Moreover, it was observed that an increase in the particle shape factor from 0.1 to 1.0 leads to a decrease of almost 70 % in the average erosion density of the hydrocyclone wall surfaces.

Alcohol delamination of the corneal epithelium for recurrent corneal erosion syndrome

AIM： To evaluate the outcomes of alcohol delamination（ALD） of the corneal epithelium for the treatment of recurrent corneal erosion syndrome（RCES） and to implement a standardized treatment protocol for this condition utilizing evidence based practice and the findings of an internal audit. METHODS： A retrospective analysis of 42 eyes of 40 patients diagnosed with RCES who were treated with ALD between January 2006 and March 2016 was conducted. Patients had 20% alcohol applied to the cornea with the use of a well for 40 s. Patients were reviewed one week later in the Outpatient Department. Outcome criteria were established based on standards from other studies in the medical literature. These included, a treatment success rate of at least 72%（defined as complete resolution of symptoms one month after treatment）, a postoperative complication a rate of 〈5%（mainly infective keratitis, and subepithelial haze）, and the absence of any detrimental effect on visual acuity in ≥95% of patients. RESULTS： The mean age at the time of ALD was 41.17±13.44 y. Patients were followed for an average of 12.8±15.65 mo. The majority were female（52.5%, n=21） and the majority of eyes treated with ALD were left eyes（62.9%, n=26）. Trauma was the primary aetiology in our study population. Treatment was successful in 73.8%（n=31） of eyes and in 75%（n=30） of patients. Recurrence occurred in 26.2% of eyes at a mean of 10.41±12.63 mo post treatment. CONCLUSION： ALD is an efficacious and cost-effective primary surgical intervention for RCES.

Effect of abrasive blasting on the internal surface of L80-13Cr tubing and casing

In this study,two sandblasting textures,namely,quartz and high-chromium(Cr)stainless steel sands,were used for sandblasting of the internal surface L80-13Cr tubing and casing.The contrastive analysis on the properties of the pipes before and after abrasive blasting was conducted,including the metallographic phase detection of the internal surface,simulating accelerated corrosion tests,and residual stress tests for the pipe after abrasive blasting.Based on the analysis results,it is explained why the API standard requires that no scale appears on the internal surface of L80-13Cr and iron contamination when internal sandblasting media are applied.The results show that abrasive blasting can effectively remove scales on the internal surface of L80-13Cr tubing and casing and improve corrosion resistance.The abrasive blasting process does not produce obvious residual stress on the internal surface of the tubing and casing.Also,the de-rusting effect of stainless sand is better than that of quartz sand,and the former does not produce iron contamination.

Rock breaking performance of the newly proposed unsubmerged cavitating abrasive waterjet

To improve the rock breaking ability, cavitating waterjet and abrasive waterjet are combined by using a coaxial low-speed waterjet generated around the periphery of a high-speed abrasive waterjet, and a new type of waterjet called unsubmerged cavitating abrasive waterjet(UCAWJ) is thus produced. The rock breaking performance of UCAWJ was compared with submerged cavitating abrasive waterjet(SCAWJ)and unsubmerged abrasive waterjet(UAWJ) by impinging sandstone specimens. Moreover, the effects of jet pressure, standoff distance, abrasive flow rate and concentration were studied by evaluating the specific energy consumption, and the area, depth, and mass loss of the eroded specimen. The results show that the artificially generated submerged environment in UCAWJ is able to enhance the rock breaking performance under the same operating parameters. Furthermore, the rock breaking performance of UCAWJ is much better at higher jet pressures and smaller standoff distances when compared with UAWJ. The greatest rock breaking ability of UCAWJ appears at jet pressure of 50 MPa and standoff distance of 32 mm, with the mass loss of sandstone increased by 370.6% and the energy dissipation decreased by 75.8%. In addition, under the experimental conditions the optimal abrasive flow rate and concentration are 76.5 m L/min and 3%, respectively.

孕镶金刚石钻头磨损机理研究

孕镶金刚石钻头通过钻头胎体的持续磨损实现金刚石的自锐和高效破岩。因此,研究金刚石钻头磨损的影响因素及其影响程度和影响机理,对孕镶金刚石钻头的设计和使用非常重要。本次研究探讨了岩石物理力学性质、钻头胎体性能和钻进工艺参数等因素对孕镶金刚石钻头磨损过程和磨损机理的影响。分析表明,对钻头磨损最为显著的影响因素是岩石中的硬质颗粒导致的磨粒磨损,其次是钻头胎体与岩粉之间的粘着磨损,以及冲洗液中岩粉颗粒导致的冲蚀磨损。在此基础上,以不同硬度的钻头胎体摩擦磨损试验结果为例,探讨了钻头胎体性能及其内部硬质点对钻头磨损的影响机理。该研究成果可为科学设计与合理使用孕镶金刚石钻头提供依据。

气门-气门座的摩擦学设计研究

介绍了气门 -气门座摩擦副的工作状况和失效形式 ,提出了气门 -气门座摩擦学设计的方法 ;计算了配气机构工作时气门的动力学状态、气门头部的应力分布和气门头部的轴向变形 ,指出了提高气门

微磨料气射流加工技术研究现状与展望

微磨料射流加工技术是一种基于高能流体的磨粒冲蚀磨损加工技术,已广泛应用于难加工材料、复杂三维型面、光滑表面的加工。为进一步提高磨料射流加工过程中的精准控形控性能力,国内外学者开展了诸多基础加工理论与工艺探索等方面的研究工作。本文在概述磨料射流加工技术发展的基础上,全面总结了国内外学者在微磨料气射流加工(MAJM)技术中的微磨料气射流束发散效应及其抑制策略、材料力学性能对材料冲蚀去除模式的影响、材料冲蚀加工过程磨料嵌入抑制策略、微结构冲蚀加工几何特征等方面的主要研究成果,并对微磨料射流加工技术的难点与发展趋势进行了展望。

可变形磨损模型下微型离心泵复合磨损研究

为了探究微型离心泵在不同颗粒体积分数下的复合磨损类型与磨损变化,基于计算流体动力学与离散元耦合的方法,通过可变形磨料磨损Archard模型与可变形冲蚀磨损Oka模型对离心泵在不同颗粒体积分数(2%、4%、6%、8%、10%、12%)下的颗粒-部件碰撞占比率、磨损分布与演化进行了研究。通过对比实验发现颗粒体积分数在4%附近时颗粒与叶轮叶片、蜗壳碰撞占比率呈现不同的变化趋势。离心泵磨损以磨料磨损为主,磨料磨损中蜗壳为磨损最严重的部件,占总磨料磨损量的68.5%,随着颗粒体积分数的增加,蜗壳处磨料磨损由断面Ⅷ向断面Ⅰ演化,蜗壳前后端先后磨损。冲蚀磨损高磨损区域主要集中于叶轮叶片,占冲蚀磨损总量的95.83%,蜗壳处冲蚀磨损断面演化规律与磨料磨损变化规律近似,但蜗壳后端最先被磨损。颗粒体积分数对蜗壳磨料磨损变形量影响较大,蜗壳、叶轮磨料磨损变形量与冲蚀磨损变形量具有相似的变化趋势。

电沉积Ni-P/纳米Al_2O_3复合镀层的摩擦磨损与耐铝液侵蚀性能

研究电沉积Ni-P/纳米Al2O3复合镀层的干摩擦磨损性能和耐铝液侵蚀性能,采用扫描电镜(SEM)观察Ni-P/纳米Al2O3复合镀层的磨损表面形貌以及铝与Ni-P/纳米Al2O3复合镀层的界面结构。结果表明:Ni-P/纳米Al2O3复合镀层(镀态)与淬火45钢对摩时的摩擦因数为0.45～0.55,磨损表现为疲劳剥落;经400℃热处理后,Ni-P/纳米Al2O3复合镀层与淬火45钢对摩的摩擦因数为0.20～0.24,磨损机理表现为轻微粘着和磨蚀;铝液在Ni-P/纳米Al2O3复合镀层表面的润湿角为109,Ni-P/纳米Al2O3复合镀层具有良好的耐铝液侵蚀性能。

基于Eros的多元时间序列相似度分析

为提高多元时间序列相似性度量的效率,采用扩展Frobenius范数(Eros)的主元分析(PCA)方法,通过主元和本征值构造主元相似因子,用于比较多元时间序列矩阵之间的相似性。为了验证这种方法的有效性,针对三组数据(两个真实数据,一个合成数据)进行了实验。结果表明,该方法相对于以往的欧几里德距离(ED),动态时间弯曲(DTW)相似性度量方法具有一定的优越性。

泥沙浓度对水力机械材料磨损及磨蚀特性的影响

多泥沙河流上运行的水力机械受到泥沙磨蚀而导致过流部件变形、破坏,严重威胁机组安全运行。本研究对水力机械常用材料开展了旋转喷射磨蚀试验,采用失重法和微观形貌分析法研究了泥沙浓度对材料磨损及磨蚀特性的影响。结果表明:材料受到冲击磨损和磨蚀的累积失重量均随泥沙浓度变化呈近线性增长;当泥沙浓度小于60 kg/m^(3)时,3种材料累积失重量随泥沙浓度增长较缓;当泥沙浓度大于60 kg/m^(3)时,材料失重量增长较快。随着泥沙浓度的增大,冲击磨蚀对材料造成更严重的破坏,但空蚀损伤呈减弱趋势,材料表面硬度越高,抗空蚀性能越好,磨损和磨蚀失重量相等的临界泥沙浓度越低。空蚀作用会影响沙粒撞击材料表面的角度,导致颗粒水平冲击载荷更大,磨痕呈现切削唇边和堆积,在更高泥沙浓度下沙粒切削破坏占据主导作用。

3种磨料对超音速火焰喷涂WC-12Co层形貌及冲蚀磨损性能的影响

目前,就冲蚀粒子性质对超音速火焰喷涂(HVOF)WC-Co层的外观、硬度及冲蚀磨损性能的影响研究不多。采用HVOF技术在Q235钢表面制备WC-12Co涂层,并以棕钢玉砂、石英砂和黄砂为磨料,采用常温干砂冲蚀磨损试验机对涂层的冲蚀磨损性能进行了测试。采用显微维氏硬度计测试不同磨料的硬度,采用扫描电镜对磨料形貌、涂层显微结构及涂层冲蚀后的表面形貌进行了观察。结果表明:WC-12Co涂层为典型的层状组织结构,扁平化粒子间结合紧密,涂层内部孔隙较均匀。冲蚀过程中,冲蚀角度从30°增加到90°,涂层的冲蚀率增加。棕刚玉砂和石英砂表面形貌呈不规则多角状,硬度较大的棕刚玉砂对涂层冲蚀磨损较大大。石英砂和黄砂硬度相近,形貌规则的黄砂对涂层的冲蚀磨损较小。不规则的多角状磨料冲蚀的涂层,表面留下不规则坑洞及较深的切痕;规则的近圆外形黄砂冲蚀的表面留下近圆形的坑洞,同时粘结相的切痕较浅。

Fe-25Mn-6Si-7Cr形状记忆合金在含沙多相流中的损伤行为

测量Fe-25Mn-6Si-7Cr形状记忆合金在含沙多相流中的损伤抗力,研究了失效机制和损伤抗力的控制因素,并与水轮机叶片用不锈钢0Cr13Ni5Mo进行了对比.结果表明,Fe-25Mn-6Si-7Cr形状记忆合金在含沙多相流中的失效机制主要是泥沙犁削,其损伤抗力因高的局域弹性和高的犁削抗力而优于不锈钢0Cr13Ni5Mo,局域弹性高是其损伤破坏速度效应低和空蚀与泥沙冲刷磨损交互作用小的根本原因.

石灰石-石膏法烟气脱硫运行中常见问题浅析

根据运行经验,就湿式石灰石-石膏脱硫工艺在实际运行中存在的诸如除雾器、GGH、浆液管道等的结垢、堵塞、磨损、腐蚀,以及石膏脱水难和机械故障等问题进行了分析讨论。