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采用激光熔覆技术在18CrNiMo7-6齿轮钢表面制备Ni基涂层,研究激光功率、扫描速度和送粉率对Ni基涂层熔覆质量和微观组织的影响,建立激光熔覆工艺参数与涂层宏观尺寸、微观组织和显微硬度之间的关系。结果表明,随着激光功率的增大,涂层的熔高、熔宽、熔深增大,微观组织细化,显微硬度增大;随着扫描速度的增大,涂层熔高、熔宽、熔深减小,微观组织粗化,显微硬度减小;随着送粉率的增大,涂层的熔高增大,熔宽先增大后减小,熔深减小,涂层微观组织细化,显微硬度增大。以涂层宏观形貌、微观组织结构和显微硬度为涂层质量评估指标,优选得到的最佳工艺参数为:激光功率700 W,扫描速度2 mm/s,送粉率11.1 g/min。 相似文献
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利用氩弧熔覆技术,以Ni60自熔合金粉、钛粉和石墨粉为原料,在45#钢表面原位反应合成了以TiC颗粒为增强相的Ni基复合涂层。利用金相、SEM、XRD等技术分析了涂层的显微组织,利用显微硬度仪测试了熔覆层显微硬度,用自制磨损试验机对比了熔覆层与淬火回火65Mn钢的耐磨性。结果表明,熔覆层成形良好,无裂纹、气孔等缺陷,与基体呈冶金结合;熔覆层的组织为γ—Ni奥氏体枝晶、CrB、TiB2、Cr23C6、Fe23C6及反应合成的弥散分布的球状TiC陶瓷颗粒;熔覆层显微硬度呈梯度分布,且越靠近基体表面,硬度越低;熔覆层具有优良的耐磨性能。 相似文献
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稀土对激光熔覆WC/Ni-P涂层微磨料磨损性能的影响 总被引:2,自引:0,他引:2
利用激光熔覆技术在45钢表面制备了WC/NNi-P复合椽层.在Plint TE-66微磨料磨损试验机上进行了磨损试验,研兜了不同稀土含量(CeO2)以及不同粒度WC粉末对涂层熔覆性能、硬度和磨损性能的影响。研究结果表明:稀土的适当加入船移使熔覆时熔体的流动性显著提高.使其气孔率降低,表面平整,能显著提高熔覆层的熔覆性能。随稀土含量增加,涂层组织细化;WC颗粒的加入提高了涂层的显微硬度和耐磨性。在微磨料磨损过程中馀层表面Ni-P基质优先于WC颗粒被磨去,导致WC颗粒从基质中凸起,最后WC颗粒失去基质支撑在磨料的作用下从涂层中脱落。 相似文献
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采用激光熔覆表面改性方法,在45号钢基体上表面熔覆Cu/WCp复合涂层。试验研究了WC含量对熔覆复合涂层的组织特点和耐摩擦磨损性能的影响规律。研究结果表明,通过调整WC的加入量可获得α-Cu固溶体+WC双相组织,当WC的加入量超过30%时,熔覆层中出现小圆点状的WC颗粒,表明WC有一定程度的熔化和熔解;Cu/WCp复合熔覆层与基体金属之间存在过渡区,其组织为钢基体+WC混合组织。采用40Cr磨轮对Cu/WCp熔覆层进行摩擦磨损试验,结果表明,WC加入量为10%时,摩擦系数与磨损量最小;采用硬质合金磨轮进行磨损试验,当WC加入量为30%时,摩擦系数最小,而加入量为10%,磨损量较小。 相似文献
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A stannate chemical conversion process followed by an activation procedure was employed as the pre‐treatment process for AZ91D magnesium alloy substrate. Zn was electroplated onto the pre‐treated AZ91D magnesium alloy surface from pyrophosphate bath to improve the corrosion resistance and the solderability. The surface morphologies of conversion coating and zinc coating were examined with scanning electron microscope (SEM). The phase composition of conversion coating was investigated by X‐ray diffraction (XRD). The electrochemical corrosion behavior of the coatings in the corrosive solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The experimental results showed that the activated stannate chemical conversion coating provided a suitable interface between zinc coating and the AZ91D magnesium alloy substrate. The corrosion resistance of the AZ91D substrate was improved by the zinc coating. 相似文献
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In this paper, a protective coating scheme was applied for the corrosion protection of AZ91D magnesium alloy. Electroless Ni coating (EN coating) as bottom layer, electrodeposited Ni coating (ENN coating), and silane‐based coating (ENS coating) as top layer, respectively, were successfully prepared on AZ91D magnesium alloy by combination techniques. Scanning electron microscopy and X‐ray diffraction were employed to investigate the surface and phase structure of coatings, respectively. The electrochemical corrosion behaviors of coatings in neutral 3.5 wt% NaCl solution were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The corrosion testing showed that the three kinds of coatings all could provide corrosion protection for AZ91D magnesium alloy to a certain extent, and the corrosion resistance of ENN and ENS was superior to EN. In order to further study the corrosion protection properties of ENN and ENS, a comparative investigation on the evolution of EIS of ENN and ENS was carried out by dint of immersion test in neutral 3.5 wt% NaCl solution. The results indicated that, compared with ENN, the ENS could provide longer corrosion protection for AZ91D magnesium alloy. It is significant to determine the barrier effect of each coating, which could provide reference for industry applications. 相似文献
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镁合金等离子喷涂Al/Al_2O_3涂层的耐腐蚀性能 总被引:1,自引:1,他引:1
采用等离子喷涂技术在AZ31镁合金表面制备Al/Al_2O_3复合涂层,测试了镁合金及表面喷涂有Al/Al_2O_3复合涂层的镁合金试样的极化曲线,研究了没有涂层、经封孔处理和未经封孔处理的喷涂有复合涂层的镁合金三种试样在浸泡腐蚀和5%NaCl盐雾腐蚀情况下的耐腐蚀性能及其腐蚀行为.结果表明,经封孔处理的Al/Al_2O_3复合涂层镁合金试样在上述腐蚀条件下的耐腐蚀性均优于镁合金和涂层未封孔处理的试样,在浸泡试验中未封孔处理的涂层试样比镁合金腐蚀更加严重,在盐雾试验中却优于镁合金. 相似文献
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采用微弧表面处理技术(微弧氧化MAO和微弧复合MCC)在AZ31B镁合金基体上制备出不同断面结构的防护涂层。通过电化学腐蚀及腐蚀疲劳测试方法,研究了MAO、MCC涂层的电化学腐蚀及腐蚀疲劳性能。结果表明,生长10 min的MAO涂层具有较好的耐电化学腐蚀性能。MAO涂层表面存在微孔和微裂纹,在应力条件下微孔和微裂纹作为疲劳断裂的裂纹萌生点,可加速裂纹的萌生与扩展,使其腐蚀疲劳寿命相较AZ31B合金基体降低了55%。而具有MCC涂层的AZ31B合金试样腐蚀疲劳极限为(64.0±5.4) MPa,比AZ31B合金基体提高了59%。在低应力载荷下(<80 MPa),微弧复合涂层试样的腐蚀疲劳强度得到明显提高。 相似文献
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《中国有色金属学会会刊》2016,26(11):2976-2987
In order to improve the corrosion resistance and microhardness of AZ91D magnesium alloy, TiN nanoparticles were added to fabricate Ni–P–TiN composite coating by electrodeposition. The surface, cross-section morphology and composition were examined using SEM, EDS and XRD, and the corrosion resistance was checked by electrochemical technology. The results indicate that TiN nanoparticles were doped successfully in the Ni–P matrix after a series of complex pretreatments including activation, zinc immersion and pre-electroplating, which enhances the stability of magnesium alloy in electrolyte and the adhesion between magnesium alloy and composite coating. The microhardness of the Ni–P coating increases dramatically by adding TiN nanoparticles and subsequent heat treatment. The corrosion experimental results indicate that the corrosion resistance of Ni–P–TiN composite coating is much higher than that of uncoated AZ91D magnesium alloy and similar with Ni–P coating in short immersion time. However, TiN nanoparticles play a significant role in long-term corrosion resistance of composite coatings. 相似文献
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An aluminum-alloyed coating was formed on an AZ91D magnesium alloy in molten salts containing AlCl3 at a lower temperature of 380 °C. The microstructure and phase constitution of the alloyed layer were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffraction. The nano-hardness of the coating was studied by nanoindentation associated with scanning probe microscopy. The corrosion resistance of the coated specimen was evaluated in a 3.5 wt.% NaCl solution by electrochemical impedance spectroscopy and cyclic potentiodynamic polarization. The results show that the aluminum-alloyed coating consists of Mg2Al3 and Mg17Al12 intermetallic layers. The formation of the coating is dictated by the negative standard free energy of the reaction: 2AlCl3 + 3 Mg = 3MgCl2 + 2Al. This process is associated with a displacement reaction mechanism and diffusion process that takes place during the molten salt treatment. High activity of Al elements in molten salts contributes to the lower temperature formation of the Al-alloyed coating. The alloyed coating markedly improves the hardness as well as the corrosion resistance of the alloy in comparison with the untreated AZ91D magnesium alloy, which is attributed to the formation of the intermetallic compounds. 相似文献
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镁合金表面等离子喷涂Al2O3-TiO2陶瓷涂层的耐腐蚀性研究 总被引:1,自引:1,他引:0
采用等离子喷涂技术在AZ31镁合金表面制备Al2O3-13%TiO2陶瓷复合涂层,对涂层的微观组织进行了观察分析,测试了涂层的表面硬度.通过极化曲线和浸泡腐蚀试验,对比研究了镁合金基材及喷涂陶瓷涂层的试样在5% NaCl溶液中的耐腐蚀性能.结果表明:涂层镁合金试样的硬度和耐腐蚀性优于基体镁合金,但当腐蚀液透过涂层孔隙时... 相似文献
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The influence of permanent-magnet-driven stirring during solidification on the microstructure and corrosion property of AZ61 magnesium alloy was investigated. The corrosion behaviour of AZ61 was studied in 3.5mol/L NaCI by measuring electrochemical polarization. The results show that the permanent-magnet stirring refines the microstructure of AZ61 magnesium alloy, which improves the precipitation amount and distribution uniformity of β phase and decreases the content of hydrogen, but it has less influence on the distribution uniformity of Zn. The change of precipitation amount of β phase influences the corrosive nature of the matrix, and it has no direct proportion with the corrosion resistance of the matrix. 相似文献