Effect of post-sintering heat-treatments on the erosive wear behaviour of liquid-phase-sintered aluminas

The influence of microstructure on the indentation-strength and solidparticle erosive wear behaviour of a liquid-phase-sintered (LPS)alumina subjected to coarsening, quenching and crystallisationheat-treatments were investigated. Strength as a function of cracksize using Vickers indentations of varying loads was assessed. Theshort-crack toughness curves (T-curves) of the materials wereevaluated from indentation-strength data which is pertinent to wearproperties, since wear is governed by fracture characteristics atsmall flaw sizes. The effects of impact angle and particle velocityon erosive wear rates were also analysed. The relationship betweenshort-crack toughness behaviour and erosion resistance are discussedwith reference to the material microstructures and phase composition.     

银-二硫化钼复合材料滑动电磨损机理的研究

采用粉末冶金方法制备银-二硫化钼复合材料,研究了材料在滑动电磨损状态下的摩擦系数、磨损量和接触电压降变化情况,探讨了电磨损发生过程的机理.研究表明:与纯机械磨损相比,电磨损过程中材料的摩擦系数差别不大;在电磨损过程中发生阳极侵蚀现象,材料从阳极向阴极发生转移,正刷的磨损量大于负刷,纯机械磨损量在二者之间;磨损过程中由于正刷侧的二硫化钼膜厚度大于负刷,以及正刷微观导电点的数量少于负刷,使得正刷的接触电压降高于负刷.     

滑动速度对碳纳米管-银-石墨复合材料电磨损性能的影响

采用粉末冶金法制备了碳纳米管-银-石墨复合材料,研究了圆周速度对复合材料摩擦系数、磨损量的影响。结果表明,当压力一定时,随着速度的加快,机械磨损的摩擦系数减小,而电磨损的摩擦系数增大;复合材料的电磨损量远远大于机械磨损的磨损量,电磨损时磨损量在V=10m/s处出现最小值,而机械磨损的磨损量随速度的加快而减小。     

纳米晶铜电火花电极快速制造及其耐电蚀性能(英文)

介绍了喷射电铸快速成形的基本原理,制备了纳米晶电极铜,分别研究了纳米晶铜电极和粗晶铜在不同电火花加工参数的工具电极损耗性能。运用扫描电子显微镜(SEM)和X-ray衍射等现代分析手段对工具电极的微观结构和成分进行分析。结果表明,喷射电铸能显著提高极限电流密度,细化晶粒,铜沉积层具有纳米晶微观结构。纳米铜电极损耗随着脉冲宽度增大而减小,随峰值电流的增大而增大,且纳米晶铜的电极损耗明显小于粗晶铜。     

真空热压烧结制备Mo10/Cu-Al_2O_3复合材料及其载流磨损性能研究

在VDBF-250真空热压烧结炉中,采用真空热压烧结工艺制备了Mo10/Cu-Al2O3复合材料,观察显微组织,并测试性能。在HST100载流高速摩擦磨损试验机上研究了载流磨损机理。结果表明,该材料致密度为98.23%,组织较为致密;显微硬度为116 HV,导电率为41.33%IACS;Mo10/Cu-Al2O3复合材料的磨损形式为粘着磨损、磨粒磨损和电弧烧蚀磨损。     

微量Zr对Cu-Ag合金磨损行为的影响

采用真空熔炼的方法制备了CuAg-Zr合金，研究了微量Zr对Cu-Ag合金磨损行为的影响，探讨了合金的磨损机理．结果表明：Cu-Ag合金的磨损率随着Zr含量的增加明显减小，随着受电电流和滑动距离的增大逐渐增大．粘着磨损、磨粒磨损和电侵蚀磨损是主要的磨损机制．微量Zr的加入使合金中形成弥散细小的析出相，使其磨损性能明显优于Cu-Ag合金．     

耐磨耐蚀钢发展途径的探索

在双相不锈钢研究基础上，探索了耐磨耐蚀合金组织与腐蚀，磨损，冲蚀性能的关系，腐蚀介质中外加极化电位下的销环磨损试验，料浆及水砂冲蚀和磨痕观测结果表明：控制合金成分及组织以提高其综合性能，并充分发挥形变强化能力是发展耐磨耐蚀合金的正确途径，第二相强化只要应用得当也有定效果。     

Investigation of erosive wear behavior and physical properties of SGF and/or calcite reinforced ABS/PA6 composites

The aim of this study was to investigate the erosive wear behavior of glass fiber, CaCO₃ particle and glass fiber/CaCO₃ hybrid reinforced ABS/PA6 blend based composites. The samples were prepared by using melt mixing and injection molding techniques. The mechanical, thermal, morphological properties and erosive wear behavior were investigated in terms of reinforcing agent type and composition. It was observed that the tensile strength and modulus values of hybrid composites gave a value between tensile strength and modulus values of only fiber reinforced composites and only particle reinforced composites. From DSC analysis it was revealed that T_g and T_m of composites were not significantly affected by reinforcement; however, degree of crystallinity was found to be sensitive to reinforcement type and composition. The impingement angle was found to have a significant effect on the erosive wear behavior. The results indicated that composite materials exhibited maximum erosion rate at impact angle of 30° conforming their ductile erosion behavior. In order to investigate wear mechanisms, eroded surface analysis was done by scanning electron microscopy. Surface analysis showed that repeated impact of hard silica sand particles caused a local removal of the matrix from the fiber surface and led to form craters on the surface of the composite material.     

不同磨粒含量下过共晶成分铝锰基复合材料的冲蚀磨损性能

采用MSH型磨损试验机将过共晶成分Al—Mn合金及A1203颗粒增强过共晶成分铝锰基复合材料在3．5m／s速度下进行不同磨粒粒度和不同磨粒含量的冲蚀磨损试验，分析了两种材料的组织结构，并对材料的失重率、抗冲蚀磨损性能、微观失效表面形貌进行了研究和讨论。结果表明：两种材料的冲蚀磨损失重率随着磨粒含量的增加明显增大；在3％磨粒加入量下二者的失重率随着磨粒粒度的增大均呈现出先增大后减小的趋势，且随着磨粒含量的增加两种材料在较大粒径下出现增重的现象消失。此外，在锰含量相近的条件下A120s颗粒增强过共晶成分铝锰基复合材料的抗冲蚀磨损性能优于过共晶成分铝锰合金。     

Microstructure,mechanical and erosion wear analysis of post heat treated iron alloy based coating with varying chromium

The present work focuses on the effect of annealing heat treatment on the microstructure, mechanical and erosion properties of iron alloy based coatings with varying chromium content. High velocity oxygen fuel coating method was used to deposit the coating over the substrate material 316 L stainless steel. The study was done in terms of microstructural analysis using x-ray diffractometer, surface and cross-sectional morphology using field emission scanning electron microscope, mechanical and erosion wear analysis. It was found that x-ray diffractometer indicated presence of less amount of titanium dioxide (TiO₂) and silicon dioxide (SiO₂) after heat treatment. However, the peaks of hardened phase of diironylidenetitanium (Fe₂Ti) and iron-chromium (Fe−Cr) was increased. Addition of chromium up to 10 wt. % improved the hardness and adhesion pull of strength by 16 % and 62 % respectively. On the other side heat treatment of iron alloy based coating having 10 wt. % chromium increased the hardness and adhesion pull off strength by 17.3 % and 35 % respectively. The erosion wear rate was also decreased with the annealing process. The study shows that the annealing process increases hardness and adhesion pull off strength but decreases porosity and erosion wear rate.     

Failure analysis of a railway copper contact strip

The present work investigated the causes of premature wear of the contact strips of a railway line working under voltage of 1.500 Vcc, current of 1120 A, normal force of 70 N and presence of graphite in the wire/strip interface. In all investigated regions (without apparent wear, moderate wear and severe wear), the presence of cracks in the hardened tribo-surface of the Cu-strip – which is caused either by work hardening or thermal cycling is usually followed by material detachment and production of hard abrasive debris. The presence of hard abrasive particles (such as SiO₂ and Al₂O₃,) and wear debris (Cu₂O and hardened Cu) promotes a regime of severe abrasion. The debris showed preferentially a flake-like morphology, being composed of graphite and highly deformed copper, suggesting the dominant action of mechanical wear mechanisms. The presence of some raindrop-like debris featuring an as-cast microstructure confirmed the occurrence of incipient fusion on the copper strip tribo-interface, possibly caused by electrical discharge (electrical induced wear). The results indicated that the wear mechanism of the Cu strip is divided into different stages. First, there is a mixed wear regime (adhesive and abrasive wear) of the graphite layer associated with lubricated adhesive wear of the Cu strip. After, there is the occurrence of a mixed wear regime between the strip/wire tribo surfaces, with simultaneous action of unlubricated adhesive wear, third body abrasive wear and electrical induced wear (local fusion). Finally, once the graphite has been completely consumed, the wear grooves are parallel to the sliding direction and the centre of the strip shows a much more severe wear rate.     

Influence of carbon diffusion on microstructure and wear behaviour of duplex stainless steel surface layers on lamellar grey cast iron

Surface welding with duplex stainless steel was performed to enhance the wear and corrosion properties of grey cast iron, which is used as material for applications as pump components in maritime and chemical environments. The method used for surface welding and the corresponding process parameters determine the chemical composition and microstructure, which both determine the corrosion and wear properties of the surface layer. High heat input leads to high chemical dilution and thus, reduced corrosion resistance. Slow cooling rates, which are recommended for welding of grey cast iron components, facilitate the formation of carbides in the fusion zone of the chromium‐rich duplex stainless steel surface layer. On the one hand, carbides lead to increased hardness and thus, improved wear resistance of the surface layers. On the other hand, carbides and high chemical dilution rates reduce the corrosion resistance and therefore should be avoided. Under high cooling rates, the risk of cracking in the heat affected zone of the grey cast iron increases due to martensitic phase transformations. The paper describes the correlation of process parameters, microstructure and chemical composition with a focus on carbon diffusion and carbide formation, ever considering the effect on the wear behaviour in an oscillation tribometer and under erosion‐corrosion conditions.     

硼对铜合金组织和性能的影响

研究了加硼铜合金的组织以及力学、腐蚀、腐蚀磨损和冲蚀性能。结果表明：硼能明显细化铜合金的组织，提高其强度、硬度，改善其耐蚀、耐腐蚀磨损及耐冲蚀能力；并确定硼在铜合金中的最佳含量范围。     

Machining Characteristics of Inconel 718 by Sinking-EDM and Wire-EDM

Inconel 718 superalloy has wide applications in several industries due to its excellent mechanical properties. However, it is very difficult to machine using conventional cutting and grinding because of its high strength at elevated temperatures. Electrical discharge machining (EDM) is an alternative competitive process to machine Inconel alloys by electrical erosion. However, machinability and surface characteristics of EDMed Inconel surfaces are poorly understood. This study focuses on the machining characteristics of Inconel 718 by Wire-EDM and Sinking-EDM with a new Cu-SiC electrode, respectively. Material removal efficiency, surface roughness, surface topography, surface alloying, and electrode wear have been characterized. It is found that the high toughness of Inconel 718 would be the major contributing factor to the absence of microcracks on the EDMed surface. The new fabricated Cu-SiC electrode for Sinking-EDM has better performance in terms of material removal rate (MRR), surface roughness, and electrode wear. The higher melting temperature and fine microstructure of SiC contribute to the lower electrode wear of the new Cu-SiC electrode than the traditional Cu electrode.     

电流密度对CNTs-Ag-MoS2-G复合材料滑动电摩擦磨损性能的影响

滑动电接触材料应具有良好的耐磨性能以及出色的导电性能,在航空航天领域中,制造先进的电接触材料尤为重要.实验中采用粉末冶金法制备CNTs-Ag-MoS2-G复合材料,研究了复合材料电摩擦磨损过程中的接触电阻及磨损率的变化,并通过扫描电子显微镜观察材料磨损后表面形貌.实验结果表明:在电流密度从5A/cm2增加到15A/cm2的过程中,复合材料接触电阻下降,体积磨损量增加,并且由于电弧侵蚀作用的影响,正刷的磨损量大于负刷,碳纳米管的特殊的基体增强作用及一定的导电导热能力使得CNTs-Ag-MoS2-G复合材料磨损量小于Ag-MoS2-G复合材料磨损量.     

Cu-Ag-Fe合金的电接触滑动磨损的研究

为改善接触线的耐磨性能,在Cu-Ag合金中添加微量Fe元素制备了Cu-Ag-Fe合金接触线,研究了电流强度、滑动速度和载荷对Cu-Ag-Fe合金的磨损形貌及磨损率的影响.实验结果表明：随电流强度、滑动速度和载荷的增加,合金的质量磨损率明显增加.磨损形貌表明,在受电滑动条件下,磨损形式以粘着磨损、磨粒磨损和电侵蚀磨损为主...     

纳米SiO_2/沥青改性环氧树脂的抗冲蚀磨损性能

为了降低强风沙流区混凝土的冲蚀磨损,常采用环氧树脂材料对其进行防护,但环氧树脂材料存在交联度高、脆性较大等缺点。为此,采用纳米Si O2和沥青对环氧树脂进行了改性,研究了改性环氧树脂的力学性能和冲蚀磨损性能,并分析了其冲蚀磨损机理。结果表明:纳米Si O2和沥青共同改性环氧树脂不仅提高了环氧树脂的拉伸强度,同时改善了环氧树脂的冲击韧性;改性环氧树脂材料表现出半塑性材料的冲蚀特征,最大冲蚀率出现在45°冲蚀角,冲蚀率与冲蚀速率呈指数关系,速率指数为2.65~3.25;1%纳米Si O2和10%沥青协同改性的环氧树脂表现出了良好的冲蚀抗力,是强风沙流环境下混凝土结构冲蚀磨损防护的可选材料。     

Structure and wear resistance of the composite layers produced by glow discharge nitriding and PLD method on AISI 316L austenitic stainless steel

The rapid technical development enhances the demands on constructional materials in terms of their resistance to frictional wear, resistance to corrosion and erosion, high hardness, high tensile and fatigue strength. These demands can be satisfied by e.g. applying various surface engineering techniques that permit to modify the microstructure, phase and chemical composition of the surface layers of the treated parts. A prospective line of the development of surface engineering is the production of composite layers by combining various surface engineering methods. The paper presents the results of examinations of the phase composition and frictional wear resistance of the layers produced by hybrid processes, i.e. such that combined glow discharge assisted nitriding performed at 450 °C and 550 °C with a pulsed laser deposition of boron nitride coatings (PLD method). It has been shown that the boron nitride coatings formed on nitrided AISI 316L steel increase its frictional wear resistance.     

Synthesis and characterisation of free standing,one­dimensional,Al–SiC based functionally gradient material

Abstract

In the present study, an aluminium–silicon carbide based functionally gradient material was successfully synthesised using a new technique termed here as gradient slurry disintegration and deposition process. The gradient of SiC was successfully established using this technique for 21 wt-%SiC. The results were confirmed using microstructural characterisation techniques, microhardness measurements, and wear rate determination. The results further revealed that an increase in the weight percentage of silicon carbide particulates along the deposition direction lead to a concurrent increase in porosity, degree of clustering, and microhardness while the nature of silicon carbide/aluminium interfacial integrity remained the same. The results of wear rate determination indicated that a difference of ～9.53 vol.-%SiC on the opposite faces of the functionally gradient material led to the wear resistance increasing to ～31.5× that of the high aluminium end. An attempt is made to interrelate the processing methodology, microstructure, microhardness, and wear rate results obtained in the present study.     

Structure and wear resistance of the composite layers produced by glow discharge nitriding and PLD method on AISI 316L austenitic stainless steel

The rapid technical development enhances the demands on constructional materials in terms of their resistance to frictional wear, resistance to corrosion and erosion, high hardness, high tensile and fatigue strength. These demands can be satisfied by e.g. applying various surface engineering techniques that permit to modify the microstructure, phase and chemical composition of the surface layers of the treated parts. A prospective line of the development of surface engineering is the production of composite layers by combining various surface engineering methods. The paper presents the results of examinations of the phase composition and frictional wear resistance of the layers produced by hybrid processes, i.e. such that combined glow discharge assisted nitriding performed at 450 °C and 550 °C with a pulsed laser deposition of boron nitride coatings (PLD method). It has been shown that the boron nitride coatings formed on nitrided AISI 316L steel increase its frictional wear resistance.