Wear resistance of Zr/WC composite coatings on Cr12MoV steel surface by electric spark deposition

Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.

Characterization and wear behavior of WC-0.8Co coating on cast steel rolls by electro-spark deposition

To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC＋8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffractometer （XRD） and scanning electron microscopy （SEM） with energy dispersive X-ray analysis （EDX）. The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe2C and Si2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhardness value of the coating is about 1573.9 Hv0.3. The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.

Interface behavior and microstructure transformation of welded joint of 35CrMo steel by electro-spark deposition

Electro-spark deposition has been carried out on the 35CrMo steel by filling and restoring the simulated slot specimens, and continuous surface coating with extra low porosity was obtained with proper parameters. The microstructure transformation and interface behavior of deposited joint were observed and analyzed. It shows that a transition region with 15μm in depth was obtained between base metal and deposited metal, and metallurgical bonding was achieved between restored base metal and deposition coating.

Tribological properties of cobalt-based alloy coating with different cobalt contents by electro-spark deposition

The cobalt-based alloy coating with different Co contents was deposited on 45 steel by electro-spark deposition with the self-made electrode. The coating has a compact and uniform microstructure with low porosity and no visible microcracks. When Co content increases grad- ually, oxygen content of coating samples 1-5 decreases first and then increases in the range of 2.52 wt%-3.05 wt%; sample 3 has the lowest oxygen content of 2.52 %. Mi- crohardness of the coating is improved remarkably com- pared with the substrate （HV 230.18）. With Co content increasing, microhardness of the coating samples 1-5 first rises slightly and then declines rapidly in the range of HV 580.61-1052.33. Sample 3 gets the maximum of HV 1052.33, which is about 4.6 times that of the substrate. The coating presents excellent wear resistance, which first increases and then decreases when Co content increases. Sample 3 shows the best wear resistance of about 6.4 times that of the substrate. Main wear mechanism of the coating is abrasive wear and fatigue wear, along with oxidation wear under high speed or heavy load conditions.

Wear characteristics of spheroidal graphite roll WC-8Co coating produced by electro-spark deposition

Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll substrate.The microstructure and properties of the coating were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） with energy dispersive X-ray（EDX） and ball-disc configuration wear tester.The results show that nanosized particles and amorphous structures prevail in the coating which is metallurgically bonded to the substrate.The microstructures of the transition zone include columnar structure and equiaxed structure.The primary phases of the coating contain W2C, W6C2.54, Fe3W3C, and Co3W3C.The results of abrasive test show that the coating has low friction coefficients（μaverage = 0.18） and the wear mechanisms are mainly abrasive wear, fatigue wear, and oxidation wear.The maximum microhardness value of the coating is about 17410 N/mm2.The study reveals that the electro-spark deposition process has better coating quality and the coating has high wear resistance and hardness.

Unweldable superalloy component repair using electro-spark deposition with high strength filler material

Nickel-base superalloy components with high Al+Ti content are difficult to weld repair using high strength filler materials with conventional welding methods like TIG welding. A feasibility study of electro-spark deposition (ESD) for unweldable superalloy component repair with a high strength filler material was carried out. SEM analysis reveals that a fully dense, crack-free, metallurgical bonded deposition layer can be obtained on the K24 substrate. The as-deposited microstructure characterizes fine cellular structure and the post weld heat treatment precipitates fine γ′particles. The room temperature tensile testing and 975℃, 196MPa stress rupture life testing indicate that ESD makes positively contribution to mechanical performance of repaired specimens. Based on these results, ESD has the potential as an effective alternative to repair of damage and defects in superalloy components, but more efforts should be made before it can be applied in engineering repair.

Reactive synthesis Ti （CN） -based metal ceramic coating by electric-spark deposition

Electric-spark deposition （ESD） was adopted for depositing a Ti（ CN） -based ceramic coating on the TC4 titanium alloy substrate using a laboratory-developed electric-spark deposition system, a nitrogen-sealed atmosphere and graphite electrode. The surface morphology, microstructure, interfacial behavior between the coatings and substrate, phase and element composition of the coatings were investigated by scanning electron microscope （ SEM ） , X-ray diffraction （ XRD ） , X-ray photoelectron spectroscopy （ XPS ） and Auger electron spectroscopy （ AES ） . Microhardness profile was measured with a Vickers microhardness tester. The results show that metallurgical bond between the coating and substrate is realized and the phase of coatings are made up of Ti（ CN ） spherocrystal and dendritic crystal, TiV and C. Ti（ CN） ceramic particles, which is in-situ synthesized by the reaction among titanium from the substrate, carbon from the graphite electrode and nitrogen from the shielding nitrogen gas, is about 600 mn and distributes dispersively among the coatings. Microharduess profile falls off with the coatings thickness increasing and the highest microhardness values of the superficial coating could be up to 1 496HV, which is six times more than that of the substrate.

Mechanism of Building-Up Deposited Layer during Electro-Spark Deposition

This paper studies the mechanism of formation of the deposit layer by (ESD) electro-spark deposition process. Inconel 738 substrates are coated with a deposited layer of NI6625 (Inconel 625). Selections of these two alloys have been done because they had wide applications and importance in the industry especially in gas turban blades in inland stations and in aircraft engines. ESD is suggested because it has a low input heat process which eliminates the effect of HAZ in these Ni-superfluous due to their sustainability to micro-cracks. The coating contains many deposited sub-layers coming from evaporated and melted micro-regions as a result of locally high heat generated by discharging a series of capacitors charged and discharged in a controlled manner between electrode and substrate material. The maximum deposition rates at the beginning of the process and decreases until been in a steady state condition due to the nature of the resultant morphology of the created surface.

Aluminizing Coating and Aluminizing-Y_2O_3 Coating Deposited by Pulsed Spark

Aluminizing coating and aluminizing-dispersed Y 2O 3 composite coating were prepared on 20 steel specimens by pulsed spark technique, which exhibited a micro-crystallized structure with grain size in the range of several ten to several hundred nanometers. It is shown that, after oxidation at 600 ℃ in air for 100 h, these two kinds of coatings have excellent resistance to high temperature oxidation and scale spallation, and the aluminizing-dispersed Y 2O 3 composite coating has even better property than the aluminizing coating. AFM, SEM, EDS and XRD were applied to analyze the surface morphology, composition and phases structure of these coatings and the oxide scale formed in oxidation. The mechanism for these coatings that how to enhance the oxidation resistance and scale spallation resistance was discussed by considering the factors, such as Al concentration on the selective oxidation of Fe-Al alloy, the effect of micro-crystallization, reactive element effect (REE) caused by dispersed Y 2O 3, etc.

基于DDS的数字脉冲电火花沉积电源研究

在电火花沉积加工中,脉冲电源的放电参数对沉积效果和加工效率有重要影响。针对传统电火花沉积电源放电参数可控性差的问题,基于直接数字频率合成(DDS)技术全数字化调制、输出稳定的特性,设计了一种数字脉冲电火花沉积电源。以单片机和DDS芯片为核心来控制斩波电路输出加工脉冲,可实现放电电压、频率等参数的较精确控制以及宽范围内的无极调节。经测试,控制及驱动模块输出信号稳定、准确且频率误差在1 Hz以内,放电电压波形可控性好,满足电火花沉积加工的要求,可用于电火花沉积加工基础研究。

AlCrNiFeTi高熵合金涂层的电火花沉积制备与摩擦磨损性能

采用真空电弧熔炼法制备直径为7 mm AlCrNiFeTi高熵合金(high-entropy alloy,HEA)作为电极,使用电火花沉积技术在304不锈钢表面成功制备了AlCrNiFeTi高熵合金涂层。通过XRD、OM、EDS、SEM、显微硬度计、摩擦磨损试验机对涂层的微观组织结构和摩擦磨损性能进行研究。结果表明,AlCrNiFeTi电极与涂层均以BCC1和BCC2简单固溶体为主,电极微观组织结构呈典型的树枝晶。涂层由沉积点堆叠铺展形成,表面均匀致密呈橘皮状、凸凹不平,为喷溅花样展开,涂层截面结构无宏观缺陷,厚度约为59.67μm。AlCrNiFeTi涂层最大显微硬度为587.3HV0.2,比基材的硬度提高了约2.45倍。随着载荷的增大,涂层的磨损机制由氧化磨损和轻微磨粒磨损转变为磨粒磨损和黏着磨损。当摩擦载荷为5 N时,磨损率为1.213×10^(-3)mm^(3)/(N·m),摩擦因数仅为0.446,涂层的磨损率较基材的磨损率减小了约28.3%。

纳米碳化钨涂层电火花沉积工艺参数试验研究

为制备满足不同要求的纳米碳化钨涂层,开展了以FS438为基体的纳米碳化钨涂层沉积试验,采用不同电容、放电频率及比沉积时间探究不同工艺参数对涂层厚度、粗糙度、质量过渡规律的影响。试验结果表明,电容和放电频率的增大均能增加涂层厚度,表面粗糙度则随着放电频率的增加而降低,低脉冲能量(50 V、40μF)下电极材料的利用率更高。涂层表面呈现溅射状液滴,元素主要来源于电极材料。该研究对于沉积过程的工艺选取具有重要参考意义。

微弧火花沉积Zr基非晶涂层的组织及性能

Ti6Al4V合金具有良好的耐蚀性能和生物相容性,已被广泛用作骨替代材料,但是Ti6Al4V的耐磨性较差。Zr基非晶合金涂层具有高强度、高耐磨、高耐腐蚀和良好的生物相容性等优点,在生物医用材料领域具有巨大的发展前景。本工作采用微弧火花沉积技术在Ti6Al4V表面制备了Zr基非晶涂层来增加其表面耐磨性,研究了非晶涂层的显微组织和显微硬度,同时针对不同摩擦时间对涂层摩擦性能和磨损行为的影响进行深入探讨。结果表明:涂层主要由非晶相、Cu 8Zr 3和ZrO_(2)相组成。涂层厚度为(150±10)μm且与基体具有良好的结合性。非晶涂层硬度值可达1252HV 0.1,约为基体的三倍。在不同摩擦时间下,涂层的磨损系数都小于基体,失重结果表明涂层具有更优异的耐磨性,摩擦时间为30 min时涂层的耐磨性为基体的4.8倍。不同摩擦时间下基体的磨损机制为磨粒磨损,涂层的磨损机制为疲劳磨损。本工作为进一步提高Ti6Al4V的耐磨性和Zr基非晶合金涂层的应用提供理论基础。

基于灰色关联分析法的电火花沉积WC-12Co涂层工艺参数优化

以WC-12Co为电极,氩气作为保护气体,在FS438钢表面电火花沉积WC-12Co涂层。选择电压、电容、频率和沉积时间为加工参数,采用正交实验方法进行实验,并对实验结果进行极差分析。对正交实验结果的涂层厚度和表面粗糙度进行无量纲化,计算其关联系数、关联度值,并进行灰色关联分析,最终实现多指标工艺参数的优化。利用光学显微镜,分析工艺参数优化后沉积层的表面形貌。结果表明:对WC-12Co涂层厚度和表面粗糙度影响最大的加工参数为电压和电容。当工艺参数为电压50 V、电容120μF、频率360 Hz、沉积时间4 min/cm^(2)时,所制备的WC-12Co涂层厚度为55.125μm,表面粗糙度为5.073μm,涂层表面较致密,光洁度较好,该涂层的厚度与表面粗糙度指标综合性能较为良好。

电火花沉积技术研究现状及发展趋势

详细介绍了电火花沉积技术的基本原理及其放电机理,从电极材料、工艺参数、沉积设备自动化及与其他技术复合加工等方面论述了该技术的研究现状和最新进展,旨在提高电火花沉积层的耐磨损、耐腐蚀及抗氧化等性能,为其试验的制定和生产提供一定的参考。最后分析了该技术的应用现状、发展中存在的主要问题以及与国外的差距,指出我国表面技术研究者未来的主要研究方向,为其在各工程领域中的推广应用提供参考。

Zr-4合金的微弧氧化研究

利用微弧氧化技术,以NaOH为电解液,对Zr-4合金进行微弧表面处理,以改善抗腐蚀性能和耐磨损性能。通过电化学极化曲线测量、往复式摩擦磨损实验对Zr-4合金的抗腐蚀性能、耐磨损性能进行测试和评价。研究结果表明上述性能与基体相比有显著提高。利用SEM观察Zr-4合金微弧氧化膜厚约60μm,氧化膜分为疏松层和致密层两部分,致密层约占总厚度的1/4,与基体结合紧密。XRD分析表明微弧氧化膜由四方相和单斜相二氧化锆组成。

钛合金表面反应电火花沉积TiN/Ti复合涂层

利用自制的电火花沉积充气密闭式保护装置和DZ 1400型电火花沉积/堆焊机,以工业纯钛TA2为电极,以工业纯氮为保护气和反应气,在TC4钛合金表面上反应电火花沉积制备了TiN/Ti复合涂层.利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线光电子仪(XPS)分析了涂层的组织、物相和元素组成,利用显微硬度计测定了涂层的显微硬度,利用自制磨损试验装置对比涂层与淬火W18Cr4V高速钢的磨损性能.结果表明,涂层与基体形成良好的冶金结合,涂层主要由钛和反应合成的TiN组成,涂层的平均显微硬度可达1 388 HV0.1,是基体硬度的6倍以上,涂层具有较好的耐磨性.

反应电火花沉积TiN／Ti复合涂层机理与性能

利用DZ-1400型电火花沉积/堆焊机,以工业纯钛TA2为电极,以工业纯氮为保护气和反应气,在TC4钛合金表面上制备了TiN/Ti复合涂层。用SEM、XRD、AES等仪器对涂层、物相、微观结构、元素组成及界面行为进行分析,测定了涂层的显微硬度,利用自制磨损试验机对比了涂层与淬火回火65Mn的磨损性能。结果表明,TiN/Ti复合涂层与基体形成良好的冶金结合,涂层主要由钛和反应合成的TiN、Ti2N相组成,组织致密、均匀、连续,涂层平均显微硬度可达1390HV0.1,约是基体硬度的6.3倍,涂层耐磨性良好。

电火花沉积反应合成TiN增强金属基复合涂层

利用自制的电火花沉积充气密闭式保护装置和DZ—1400型电火花沉积机,以工业纯钛TA2为电极,以工业纯氮为保护气和反应气,在45钢试件表面上电火花沉积反应合成制备了TiN增强金属基陶瓷复合涂层。利用X射线衍射仪测定了涂层的物相组成,利用扫描电子显微镜观察分析了涂层的显微组织结构,利用硬度仪测试了涂层的显微硬度,利用自制磨损试验装置对比了涂层与淬火W18Cr4V高速钢的耐磨性能。结果表明,涂层与基体结合致密,涂层主要由电极材料钛、原位自生的TiN和基体材料铁组成,涂层的平均显微硬度可达1323HV0.1,涂层具有较好的耐磨性。

微弧氧化技术及其发展

主要介绍微弧氧化技术的工艺机理、微弧氧化膜的制备方法、影响制备的因素以及氧化膜的结构和性质,并指出了该项技术的优点和不足。