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在热喷涂工业生产过程中,喷涂制备不同材料体系的涂层之前需要对送粉路径(送粉罐、送粉盘、搅拌器、送粉管路、送粉针)进行清理,但由于送粉路径内部结构复杂且存在静电吸附效应,使得残留于喷涂系统的粉末无法被完全去除,通常以微量杂质颗粒的形式被带入新涂层,进而影响新涂层的性能。为此,本文研究了在单晶基材表面采用高速火焰(HVOF)喷涂制备MCrAlY涂层过程中,送粉路径残留的WC杂质颗粒(WC-10Co4Cr)在涂层及涂层与基材界面处的遗传演变行为,分别采用SEM、EDS分析了WC杂质在喷涂态、热处理态涂层中的微观组织和相组成。研究结果表明,WC杂质颗粒确实存在于MCrAlY涂层中,并在后期热处理及氧化试验中进一步分解而固溶于涂层中,甚至扩散至单晶基材内部引起含W碳化物的生成,影响涂层及单晶基材的显微组织,改变局部的成分均匀性。同时,本文还采用ThermoCalc软件进行了热力学计算模拟,辅助分析了WC分解及W与C元素在显微组织中的遗传特性。对于WC类粉末和MCrAlY粉末共用的HVOF喷涂设备,建议给MCrAlY粉末配备单独的送粉路径,以确保涂层的纯净度与质量。 相似文献
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《中国稀土学报(英文版)》2021,39(10):1238-1245
Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm~2 and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process. 相似文献
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《International Journal of Hydrogen Energy》2020,45(51):27575-27586
This work demonstrates the effect of tin (Sn) doping on the manufacturing, electrochemical performance, and carbon deposition in dry biogas-fuelled solid oxide fuel cells (SOFCs). Sn doping via blending in technique alters the rheology of tape casting slurry and increases the Ni/ScSZ anode porosity. In contrast to the undoped Ni/ScSZ cells, where open-circuit voltage (OCV) drops in biogas, Sn–Ni/ScSZ SOFC OCV increases by 3%. The maximum power densities in biogas are 0.116, 0.211, 0.263, and 0.314 W/cm2 for undoped Ni/ScSZ, undoped Ni/ScSZ with 3 wt% pore former, Sn–Ni/ScSZ and Sn–NiScSZ with 1 wt% pore former, respectively. Sn–Ni/ScSZ reduces the effect of the drop in the maximum power densities by 26%–36% with the fuel switch. A 1.28–2.24-fold higher amount of carbon is detected on the Sn–Ni/ScSZ samples despite the better electrochemical performance, which may reflect an enhanced methane decomposition reaction. 相似文献
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《中国稀土学报(英文版)》2021,39(11):1409-1414
(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process. Effects of Ho contents on the corrosion resistance and mechanical properties of (Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester, an electrochemical workstation, a microhardness tester, a bending tester, a scanning electron microscope and an X-ray diffractometer. Results show that the addition of Ho can change the main phase structure, optimize the distribution of rare-earth rich (RE-rich) phases in grain boundary, and improve the corrosion resistance and mechanical properties of NdFeB magnets. When the content of Ho increases from 0 to 21.0 wt%, the weight loss of magnets decreases from 2.672 to 0.933 mg/cm2, and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa, respectively. 相似文献
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采用超音速火焰喷涂技术(high velocity oxygen-fuel, HVOF)制备了纳米结构、亚微米结构及常规结构的WC-10Co4Cr涂层, 研究了沉积过程中颗粒尺寸对WC脱碳行为的作用, 分析了WC颗粒尺寸对复合涂层微观组织、硬度、断裂韧性及界面结合强度的影响。结果表明: 随着WC颗粒尺寸的增大, WC脱碳率和涂层孔隙率先增大后减小, 而涂层硬度和断裂韧性先减小后增大, 界面结合强逐渐降低。在100 g压痕载荷下, 亚微米和常规结构涂层硬度的Weibull分布呈双峰特征, 而在300 g压痕载荷下, 3种结构涂层硬度的Weibull分布均呈单峰特征, 这是3种结构涂层的WC脱碳程度、层间结合力和孔隙率综合作用结果。WC-10Co4Cr纳米结构涂层呈现出低脱碳率、高硬度、高界面结合强度和适中断裂韧性的优异综合性能。 相似文献
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本文通过真空雾化方法制备原位自生(Cr,Fe)_7C_3/Fe_3Al粉末,采用显微硬度,SEM,TEM,XRD等分析方法对制品的成分,表面形貌,物相组成,及硬度等进行初步分析。研究结果表明,(Cr,Fe)_7C_3/Fe_3Al粉末硬度较Fe3Al粉末有明显提高,同时急速冷却状态下,Fe_3Al粉末与(Cr,Fe)_7C_3/Fe_3Al粉末中基体相皆由DO_3型有序相Fe_3Al组成,Cr以固溶方式存在于基体中。(Cr,Fe)_7C_3以类珠光体团簇状均匀弥散分布在基体之中,碳化物保持Cr_7C_3点阵类型,Fe原子固溶在其中。 相似文献
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通过控制旋锻程度得到3组不同加工程度的铈钨阴极,分别通过金相显微镜和扫描电子显微镜来观察旋锻过程中晶粒和第二相的变化情况;对3组样品进行了点灯测试并观察了阴极烧损情况。结果表明,与一次、三次旋锻样品相比,二次旋锻样品性能良好,主要表现为晶粒较细,第二相颗粒趋于球形且分布均匀,阴极老练时间短,着火电压低且基本稳定无变化,200 000次点灯实验后烧损较轻。 相似文献
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