Investigation of coatings produced by the electrospark machining method of steel 45 with electrodes based on carbides of tungsten and titanium

The article is devoted to the development and investigation of tungsten-containing and tungstenless electrode materials for electrospark alloying using additives of boron-containing minerals, as well as aluminum-oxide nanopowder. The kinetics of the mass transfer process with the electrospark alloying of coatings was investigated. The phase composition, roughness, and kinetics of high-temperature oxidation of coatings were studied. The anticorrosive properties of obtained coatings were studied in 3% NaCl solution by the method of impedance spectroscopy. An improvement of the barrier properties of TiC–Ni–Mo coatings with increasing datolite concentrate was revealed.     

Electrospark Graphite Alloying of Steel Surfaces: Technology,Properties, and Application

Regularities in the influence of processing time and discharge energy on the thickness, microhardness and roughness of carburized cases during electrospark graphite alloying of steel surfaces are studied and quantitative data on them are obtained. The thickness of the strengthened layer increases with gains in discharge energy and alloying time. Specimens of 40Kh, 38KhMYuA, 40KhN2MYuA, 30Kh13, Armco iron, 12Kh18N10T steels and 20 steel, as well as EGe-4 graphite are studied. The tests were carried out using the following devices: EILV-8А, EILV-9, Elitron-22А, and Elitron-52А, which provide discharge energy in the range from 0.1 to 6.8 J. Experiments show that case depth and microhardness under the same process conditions are differ significantly for various steel grades. Case depth increases with higher initial carbon contents in steel. The greater the discharge energy, the greater this difference is. Wear tests show that the method of nonabrasive ultrasonic finish processing after graphite electrospark alloying is effective, and it allows increases in the wear resistance of specimens by a factor of 7.8 for 40Kh steel and by a factor of 11.5 for 12Kh18N10T steel. Research confirms that the stage electrospark alloying of the surface of a specimen after carbonization with a graphite electrode effectively decreases roughness. Discharge energy is lowered at each stage. The stage graphite electrospark alloying of the 38KhMYuA steel case allowed decreases in the surface roughness from R _а = 11.9–14.0 μm to 0.8–0.9 μm. Industrial tests show that graphite electrospark alloying offers can accomplish a number of practical tasks.     

H13钢表面电火花沉积Nb涂层组织与性能研究

目的提高H13钢表面的力学性能和耐蚀性,延长模具的使用寿命。方法用Nb棒作为电极,氩气作为保护气体,通过电火花沉积技术在H13钢表面制备Nb沉积层。利用扫描电子显微镜分析沉积层的表面形貌、显微结构及磨痕形貌,利用X射线衍射仪分析沉积层的相组成,利用能谱仪分析沉积层的元素分布,采用显微硬度计和磨损试验机测试沉积层的显微硬度和耐磨性,采用电化学工作站对沉积层进行耐蚀性测试。结果 Nb电火花沉积层表面呈橘皮状,具有一定的粗糙度,主要由Fe_2Nb和Fe_(0.2)Nb_(0.8)等相组成。沉积层截面组织连续、致密,无明显缺陷,强化层内存在大量的微晶组织和非晶组织。Nb涂层与基体发生了元素的相互扩散和冶金结合的过程。沉积层显微硬度高达642HV,为基体的3.2倍。在同等磨损条件下,Nb沉积层磨损失重约为基体的1/3,磨痕较浅。沉积层在3.5%NaCl溶液中的电化学自腐蚀电位比基体提高了113 mV,自腐蚀电流密度显著降低。结论在H13钢表面电火花沉积Nb涂层,可有效提高其表面的显微硬度、耐磨性和耐蚀性,从而延长模具的使用寿命。     

A modified electrospark alloying method for low surface roughness

A modified electrospark alloying method has been developed. The method allows the formation of deposits with low surface roughness compared to that of the conventional electrospark alloying method. It is based on the employment of a sequence of identical pulse groups. The process of electrospark deposition and the process of electrospark grinding were combined by forming pulse groups consisting of a high energy pulse for mass transfer from treating electrode to substrate and low energy pulses for grinding during deposition. Low as-deposited surface roughness was succeeded by properly selecting parameters of the pulses in a group and pauses between them. Experimental results revealed that the proposed method is useful in forming one-two layers of deposition.     

Electrospark WC–Co coatings with different iron concentration

The effect of the iron concentration in WC–Co electrode materials on the structure and properties of coatings produced by electrospark alloying (ESA) on low-carbon steel is investigated. The effect of the iron concentration on the mass transfer and thickness of the deposited coatings is described. The phase composition, surface roughness and wear resistance of the coatings in dry and microabrasive friction are investigated. It is shown that the rate of decarbidization of tungsten carbide in ESA with a higher iron concentration of the electrode materials increases.     

双粗糙表面的微动磨损行为研究

目的 建立符合实际情况的粗糙表面微动磨损模型,准确揭示连接结构的磨损机理.方法 利用ABAQUS有限元软件中的UMESHMOTION子程序和能量耗散模型,建立粗糙表面的微动磨损模型,并探究不同表面粗糙度、材料和振动频率对粗糙表面微动磨损的影响.结果 在外部载荷、振动频率和材料相同的情况下,下试件表面粗糙度为0.2μm的...     

Investigation of the effects of electrode orientation and fluid flow rate in near-dry EDM milling

This research investigates the effects of electrode lead and tilt angles and dielectric fluid flow rate on material removal rate, tool electrode wear ratio, and surface roughness in near-dry electrical discharge machining (EDM) milling process. Computational fluid dynamics (CFD) model is developed to predict the dielectric fluid flow rate and qualitatively compare with the experimentally measured EDM material removal rate. The optimum lead angle, which maximized material removal rate and minimized tool electrode wear ratio, was found. The decrease in the lead angle has a negative effect on the roughness of machined surface. The increase in tilt angle reduces the material removal rate and increases the tool electrode wear ratio. The change in tilt angle does not have a significant effect on the surface roughness and can be used to prevent gouging in finishing EDM milling. This study shows that the material removal rate is linearly proportional to the mass flow rate of air and kerosene mixture, the tool electrode wear ratio is inversely related to the mass flow rate of air and kerosene mixture, and the average surface roughness does not have a good correlation with the flow rate of the mixture.     

The development of criteria for evaluating the effectiveness of the surface layer formation and its properties in the process of electrospark alloying. Part I. The state of the issue. Kinetic and functional criteria of the efficiency of a doped layer’s formation

The paper shows the efficiency of electrospark alloying (ESA), based on the studies of the formation of a doped layer (DL) under different processing conditions, and the properties of the surface layer and the roughness parameters. The article proposes the kinetic and functional criteria for evaluating the effectiveness of the spark alloying process, allowing us to select the material for a doping electrode and processing modes for the maximum thickness of the DL and its continuities, as well as taking into account the changes in its physicochemical, strength, and performance properties and parameters of the surface relief.     

增韧莫来石陶瓷加工表面的耐磨性分析

本文应用表面粗糙度参数和磨损率，研究增韧莫来石材料磨削，珩磨及平顶珩磨表面的耐磨性能，通过Ra，表面轮廓，支承长度率曲线，轮廓高度幅度分布图，轮廓峰谷比等粗糙度参数评定其加工表面的耐磨性。试验结果表明，增韧莫来石加工表面的磨损率高于原始烧结表面。材料的表面粗糙度影响其耐磨性，材料的磨损率随其表面粗糙度参数Ra值增大而增大，陶瓷表面的耐磨性与加工方式有关，平顶珩磨表面的耐磨性较好。     

表面纳米化对316L不锈钢干摩擦性能的影响

目的研究表面纳米化316L不锈钢干摩擦磨损性能,以获得合理的喷丸时间,提高316L不锈钢的使用寿命。方法采用普通喷丸强化方法对316L不锈钢进行表面纳米化处理,利用洛氏硬度计测量了纳米化前后材料表面洛氏硬度;利用激光共聚焦显微镜观察了纳米化前后材料表面三维形貌,测量了材料表面的粗糙度;利用扫描电子显微镜观察了表面纳米化处理后横截面的金相组织;利用材料表面性能综合测试仪在干摩擦条件下进行了摩擦磨损实验,测量了材料的摩擦系数;利用扫描电子显微镜观察了磨痕表面形貌,分析了材料的磨损机理。结果与未纳米化试样相比,喷丸时间为15 min时,表面硬度提高9.7%,而表面粗糙度降低17.6%,干摩擦系数降低17.3%;喷丸时间为30 min时,表面硬度提高34.1%,粗糙度降低35.1%,干摩擦系数降低28.8%。未纳米化试样呈现典型的粘着磨损和磨粒磨损机制,而纳米化处理后试样则主要呈现疲劳磨损和磨粒磨损机制。结论表面纳米化处理后试样表面硬度随处理时间的增加而增加,粗糙度随处理时间的增加而降低,干摩擦系数随处理时间的增加而减小。喷丸处理时间较短时以疲劳磨损为主,处理时间较长时以磨粒磨损为主。     

Electrospark alloying of titanium and its alloys: The physical, technological, and practical aspects. Part I. The peculiarities of the mass transfer and the structural and phase transformations in the surface layers and their wear and heat resistance

A detailed analysis of the works concerning the electrospark alloying of the surface of titanium and its alloys to improve their physicochemical properties and performance characteristics has been carried out. It has been shown that the electrospark alloying method makes it possible to enhance some important features of titanium such as its wear resistance, heat resistance, and corrosion stability.     

电子束改性40Cr材料表面微动摩擦磨损性能分析*

利用强流脉冲电子束技术对齿轮常用材料40Cr进行表面改性,利用光学显微镜、X射线衍射仪、粗糙度仪、显微硬度仪和摩擦摩损仪对比分析40Cr材料表面电子束改性前后的材料表面形貌、组织和力学性能及其对摩擦磨损性能的影响。结果表明:40Cr材料经电子束处理后,表面粗糙度增加,截面硬度在表层1mm内增加,材料表层组织结构由于重熔快冷发生变化而产生残余奥氏体,硬度和组织的变化都起到改善材料微摩擦磨损性能的作用。电子束改性样品摩擦因数在实验初期相对稳定,随着摩擦磨损试验的进行,摩擦因数急剧升高并接近于电子束改性前的样品。微动摩擦性能得到提高,磨损量相当于改性前的26.4%,降低近4倍。     

超声表面滚压加工对20CrMoH钢摩擦磨损性能的影响

目的 提高20CrMoH钢的耐磨性能.方法 设置不同的超声滚压力(700、1000、1300 N)与次数(3、6次),对20CrMoH钢进行超声表面滚压加工.采用扫描电子显微镜、粗糙度测量仪、光学显微镜、显微硬度测量仪、X射线应力分析仪、端面型滑动磨损试验机和3D形貌仪等设备,分别对加工前后试样的表面形貌、粗糙度、金相...     

Tribological approaches to material removal rate during chemical mechanical polishing

In this study, the effect of the friction and wear of a polishing pad on the material removal rate of a silicon oxide wafer was investigated during chemical mechanical polishing (CMP) with ceria slurry. Further, the effect of surface properties of the polishing pad, such as surface roughness and hardness, on the variation in the material removal rate was examined. From a tribological viewpoint, the in-situ friction force was monitored during the CMP process, and wear of the polishing pad was controlled by different types of conditioners. After CMP, the pad surface roughness was measured by optical profiling and scanning electron microscopy. Experimental results showed that the material removal rate was almost linearly proportional to the friction force between the pad and the wafer surface, irrespective of the properties of the pad. Experiments on the dependency of the pad wear rate on the material removal rate showed that the material removal rate increased with a decrease in the pad wear rate. Experiments and pad characterization confirmed that such a correlation was attributed to the pad surface roughness and the friction force.     

Optimization of the composition, structure, and properties of electrode materials and electrospark coatings for strengthening and reconditioningof metal surfaces

The structure and phase composition of Ni-Cr-Al alloys doped with Si, Ti, Mn, and Co have been studied. An eutectic three-phase structure was found to be in the doped alloys. Doping with Si and Ti increases the microhardness and wear resistance of the alloys. The highest coefficient of the mass transfer (0.75) during the electrospark alloying is observed for Co-containig alloys. The coatings with the doped alloys have a higher wear resistance than those with the Ni-Cr-Al basic alloy. Steel 45’s heat resistance is increased after the electrospark doping with Si-, Ti-, Mn-, and Co-containing alloys by 4, 4.3, 5.1, and 4.6 times, respectively. The electrode materials have been developed for the electrospark reconditioning of workpieces based on PE8418 (Ni-Ni₃B-Cu-Si) with the additions of titanium carbide, chromium carbide, and tungsten carbide, which make it possible to manufacture coatings up to 5-mm thick. The results of the investigation of the erosion properties of B₄C-TiB₂ alloys manufactured using the method of reactive sintering under hot pressing of B₄C-TiO₂ powder blends that were used as the electrode materials for the electrospark hardening of titanium surfaces are presented. The tests show that, in the surface layers of the electrode materials, under the impact of the electric discharge, the boron carbide content substantially decreased, while the quantity of titanium borides increased and new phases of TiC _x N _y , TiO₂, and Ti appeared. Only these components are transferred onto the surface of the titanium alloy and form there a protective coating up to 100 μm thick with high hardness (32–43 GPa) and wear resistance. The materials developed are promising for their application as the electrodes in the electrospark alloying of construction steels and titanium alloys.     

Electrospark alloying for deposition on aluminum surface of Al-Sn coatings and their wear resistance under dry friction

Some aspects of coating deposition on aluminum substrate by electrospark alloying with toolelectrode from Al-Sn alloy stimulating the SnO₂ nanofibers formation in coatings have been studied. Wear resistance of such coatings, under dry friction conditions, in conjunction with a counterbody from hardened steel has been investigated. The conditions under which the coatings thus obtained manifest the of effect of the maximal wear excess of the counterbody compared to the wear of the coatings containing SnO₂ nanofibers have been specified. The effect reaches its maximum value under the dry friction after the treatment of the surface in the mode of “sparking” at a constant energy supply in the spark gap: at high rates of the tool electrode movement with respect to the specimen and at relatively large times of the electrospark effect on the treated surface.     

Application of graphite in electrospark technologies

The results of the investigation of the use of graphite as the anode in electrospark alloying in order to form coatings on the surface of work pieces made of steel, titanium, and copper alloys to enhance their wear, friction, and corrosion resistance.     

铝合金天线钎料铺展程度及钎焊工艺控制研究

100件铝合金天线组合中,发现有21件发生钎料流出堆积。天线组合由5层3A21原材料板真空钎焊而成。对天线和原材料板材表面粗糙度、晶粒组织、析出相、焊缝组织、维氏硬度进行对比检测,并进行热处理对比实验,分析影响天线真空钎焊质量的多个因素,确认钎料在板材表面铺展程度不同的主要因素之一为表面粗糙度。失效件原材料存在晶粒较大、硬度较低的情况,通过严格控制板材热处理温度在再结晶温度以下以及板材晶粒尺寸,此类失效没有再次发生。     

A novel approach to quantifying tool wear and tool life measurements for optimal tool management

It is a common practice in batch production to continually use the same tool to machine different parts, using disparate machining parameters. In such an environment, the optimal points at which tools have to be changed, while achieving minimum production cost and maximum production rate within the surface roughness specifications, have not been adequately studied. The tool wear index (TWI) and the tool life model developed in this study use a novel approach, analyzing wear surface areas and material loss from the tool using micro-optics and image processing/analysis algorithms. With relation to surface roughness, the TWI measures the wear conditions more accurately and comprehensively, and the tool life model enables maximum use of a worn tool and minimum risk for in-process tool failure. The TWI and a surface roughness control model are integrated into an optimal control strategy that shows potential for productivity improvement and reduction of manufacturing cost.     

Electrode materials for electrospark alloying of machine parts

The conditions of producing tungsten alloys with chromium and molybdenum by thermal reduction methods of a scheelite concentrate with the additions of oxides of alloying elements are studied. The application of W–Cr and W–Cr–Mo alloys for electrospark alloying of the surface of machine parts increases the wear resistance of the parts 1.5–2 times.