Disintegration of Composite Electroexplosive Coatings in Spark Erosion

A mathematical model is proposed for the destruction of electroexplosive W–Cu, Mo–Cu, W?C–Cu, Mo–C–Cu, Ti–B–Cu, and TiB₂–Cu composite coatings under spark erosion associated with the opening of electrical contacts. The model describes the evaporation of the electrodes under the action of the heat flux due to sparking when the electrical contacts open. In this model, the resistance of the electrical contacts during the tests is assumed to be 40–50 μΩ. The model corresponds to the heating of a half-space by a normal pulsed surface heat source uniformly distributed over an area of specified radius, with a specified heating time. The energy distribution of the pulse over time is approximated by a rectangular pulse. The finite pulse length is taken into account in solving the heat-conduction equation in cylindrical coordinates for a plane instantaneous heat source. The vapor pressure of the metal is determined from the surface temperature. The calculations assume a contact voltage of 380 V; a current of 3 A; a spark discharge of length 150 μs; and a discharge–surface contact spot of radius 152 μm. The following parameters are determined: the surface temperature of pure electrodes; the surface temperature of the composite coatings; the depth of the evaporation layer for pure electrodes; the mass loss of the composite coating after a single discharge pulse; the relative change in bulk resistance of the pure electrodes and composite coatings to electroerosion; and the relative change in mass resistance of the pure electrodes and composite coatings to electroerosion. The content of the elements in the composite coating is determined. The model results are in good agreement with experimental data, especially for the ternary systems W–C–Cu, Mo–C–Cu, and Ti–B–Cu. The results are also in adequate agreement with literature data. For the binary systems W–Cu and Mo–Cu, the discrepancies may be attributed to the approximations made in the model.     

Wear-Resistant Layered Electrospark Coatings Based on ZrB2

We have studied the composition and tribological parameters (coefficient of friction and wear rate) of coatings obtained in electrospark alloying (ESA) of steel 45 with the composite ceramic ZrB₂ – SiC – B₄C based on zirconium diboride. We have shown that layer-by-layer electrospark alloying using Ti – Al – N composites to form an undercoat reduces the coefficient of friction of the coating down to 0.12-0.20 while maintaining a rather low wear level (7-11 μm/km). We have analyzed the effect of the composition of the secondary structures which are formed during tribo-oxidation under dry friction conditions.     

Hybrid Technology Combining Vacuum Electrospark Alloying,Cathodic Arc Evaporation,and Magnetron Sputtering for the Deposition of Hard Wear-Resistant Coatings

Russian Journal of Non-Ferrous Metals - A novel technology for the deposition of multilayer coatings is proposed. This technology combines electrospark alloying (ESA), pulsed arc evaporation (PAE),...     

磁控溅射涂层的耐蚀性

通过采用磁控溅射工艺,将两种铁基和镍基材质的靶材溅射到基材(1Cr18Ni9Ti)上,形成4种薄膜。对靶材、基材和薄膜等分别在不同浓度硫酸中的耐腐蚀性进行了测量,并对薄膜在0.05mol/L硫酸中的耐点蚀性进行了研究。通过对Tafel曲线、循环极化曲线及显微组织的分析,结果表明:溅射后薄膜组织为微晶,薄膜的耐蚀性普遍比溅射材前靶的耐蚀性要好;薄膜耐点蚀性很好。     

Structure and Properties of Wear-Resistant Detonation Coatings Based on Titanium Carbonitride

An investigation was made of the composition, structure and wear rate of detonation coatings on steel 30KhGSNA deposited from composite powders based on TiC_0.5N_0.5 with refractory additions of SiC, AlN, and a Ni – Cr metallic binder. It was shown that at a load of 10 MPa coatings based on titanium carbonitride exhibit substantially less wear and a larger range of sliding velocities with a stable value of wear than coatings of the hard alloy VK15 (WC – 15% Co). The physico-chemical reactions in the process of tribo-oxidation were analyzed.     

Industrial Electron-Beam Equipment for Deposition of Protective Coatings: Overview

Powder Metallurgy and Metal Ceramics - The current development of industrial electron-beam equipment for the deposition of protective coatings on gas turbine blades by high-speed electron-beam...     

Preparation of Wear-Resistant Chromium Coatings Using Different Types of Nanodiamonds

We compare the characteristics of electrochemical chromium-diamond coatings obtained using nanodiamonds made by detonation synthesis and static synthesis (0.1/0). We have studied chrome-plating in standard and dilute electrolytes, making it possible to obtain hard chromium at a temperature of 45 to 48°C and a current density from 50 to 130 A sol;dm², and also wear-resistant chromium at 52 to 56°C and a current density of 50 A/dm². We have established that the microhardness increases by 30 to 35% only in the high current density region, and to a greater degree when detonation synthesis nanodiamonds are used. On the other hand, the wear-resistance of the coating is higher when static synthesis diamonds are used, but in this case counterface wear is higher. Furthermore, static synthesis diamonds do not improve the dissipating power of the electrolyte, on which the uniformity of the coating depends. We have established that with respect to overall properties, it is preferable to use detonation synthesis nanodiamonds compared with conventional diamonds of the same size.     

Effect of Production Parameters on the Structure of the Outer Ceramic Layer in Two-Layer Metal - Ceramic Coatings Prepared by Electron-Beam Deposition in One Production Cycle

The effect of production parameters for electron-beam deposition of two-layer metal - ceramic coatings in one production cycle on the structure and phase composition of the outer ceramic layer based on zirconium oxide stabilized with yttrium oxide is studied. It is shown that it is possible to obtain metal - ceramic coatings with the required functional properties in one production cycle.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 41–48, March–April, 2005.     

磁控溅射AuNi5的热处理

采用磁控溅射方法制备了AuNi5/Ni两层复合材料中的AuNi5膜层，并对样品进行退火处理。应用金相显微分析，划痕法和SEM，研究了AuNi5膜层的结构及性能特点，经退火后，分析了AuNi5膜层与Ni基体层间的元素互扩散，结合强度及应力与热处理工艺的关系。Ni层的处理和表面状态对AuNi5膜层和Ni金属层间的结合强度有重要的影响。     

Features of the Formation of Wear-Resistant Coatings from Powders Prepared by a Micrometallurgical Process of High-Speed Melt Quenching

Metallurgist - Development of compositions and application of coatings by cold gas-dynamic deposition from powders prepared by means of a micrometallurgical method is studied. In addition, use of...     

Electron-Beam Surface Treatment of Titanium Alloy Ingots. Part 2

Metallurgist - On the basis of results of modelling [1] a series of experiments is conducted for electron beam treatment (EBT) of titanium alloy VT6, VT20, VT22, and VT3-1 ingots 400 and 600 mm in...     

Electron-Beam Surface Treatment of Titanium Alloy Ingots. Part 1

Metallurgist - A scheme for electron-beam melting (EBM) is selected on the basis of analyzing and systematizing accumulated data for electron-beam treatment of an ingot surface. In order to...     

Production of Granulated Relite by High-Speed Electron-Beam Evaporation

Powder Metallurgy and Metal Ceramics - The conditions of high-speed vacuum evaporation–condensation for producing granulated relite (a eutectic alloy of tungsten monocarbide and semicarbide)...     

工艺参数对Sm-Fe超磁致伸缩薄膜沉积速率的影响

采用磁控溅射在聚酰亚胺薄膜以及黄铜等基片上成功制备出Sm-Fe超磁致伸缩功能薄膜,并且较深入地研究了溅射功率、工作气压、靶基距以及沉积不同阶段等主要工艺参数对沉积速率的影响规律。结果表明:随溅射功率的减小和靶基距的增大,会不同程度地引起沉积速率的下降;随着工作气压的增大,最初沉积速率不断增大,当溅射气压增大到一定程度(1.5Pa)时,沉积速率达到最大值,之后随溅射气压的增大,又不断减小;对于黄铜和聚酰亚胺基片,溅射初始阶段的沉积速率低于后面阶段的沉积速率。     

Study and Application of Heat Treatment of Multi-Element Wear-Resistant Low-Alloy Steel

The effects of heat treatment on the properties of multi-element wear-resistant low-alloy steel (MLAWS) which is used to make the liner of rolling mill torus were researched. The results show that when quenching temperature is lower than 900 ℃, the hardness increases with the increase of temperature, and when quenching temperature is higher than 900 ℃, the hardness decreases with the increase of temperature. As quenching temperature is lower than 920 ℃, the effect of quenching temperature on the impact toughness is not obvious. When quenching temperature is higher than 920 ℃, impact toughness decreases with the increase of temperature. When tempering temperature is higher than 450 ℃, the hardness begins to decrease obviously. After tempering at 350 ℃, the best wear resistance was obtained. According to the service condition of rolling mill torus liner, the MLAWS is quenched from 900-920 ℃ and tempered at 350-370 ℃.     

化学成分对耐磨铸钢组织与性能的影响

为了克服高锰钢作为履带板材料具有的耐磨性能较差、力学性能较低的缺点,设计了能够作为高锰钢替代材料的一种新型双相(马氏体+贝氏体)耐磨铸钢.研究结果表明:试验钢在淬火回火态下为马氏体+贝氏体双相组织,另外还残存着极少量的残余奥氏体组织.含碳量的增加使试验钢的冲击韧性和延伸率趋向降低.随着铬含量的升高,冲击韧性在淬火回火态下升高.含质量分数为0.30%C,0.6%Cr合金的综合力学性能最优,组织为马氏体+贝氏体双相组织.经由400 h磨损试验后,在干态磨损条件下,其耐磨性能比高锰钢提高了56%,而在有腐蚀介质的湿态磨损条件下,耐磨性能比高锰钢提高了22.5%.     

复合变质处理对铸态耐磨钢夹杂物形态和性能的影响

研究了稀土硅钙镁（Re-Si-Ca-Mg）复合变质处理对铸态复相耐磨钢中夹杂物形态和性能的影响，结果表明：复合变质处理可显改变复相耐磨铸钢中夹杂物的形态和分布，这对复相耐磨钢的冲击韧性有明显的影响。