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采用5 kW CO2激光器在低碳钢表面熔覆Ni基合金层及TiB2/Ni基合金金属陶瓷涂层,研究了两种涂层的组织、显微硬度以及滑动磨损特性.结果表明,Ni基合金层主要组成相为γ-(Ni,Fe),Cr23C6等,TiB2/Ni基合金复合涂层组成相主要有γ-(Ni,Fe),Ni3B,TiB2和TiC等;Ni基合金层由发达γ-(Ni,Fe)枝晶和其间共晶组织所组成,TiB2/Ni基合金复合涂层典型组织为等轴固溶体以及其间细小共晶组织;TiB2对熔覆层的组织有显著的影响,使熔覆层组织细化,并由树枝晶转变为等轴晶;加入TiB2可显著提高Ni基合金涂层的显微硬度及耐磨性能. 相似文献
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激光熔覆镍基金属陶瓷涂层组织与高温磨损性能的研究 总被引:1,自引:1,他引:1
通过显微组织观察及高温干摩擦磨损试验,对激光熔覆镍基金属陶瓷涂层及其高温干摩擦磨损性能进行了研究。结果表明,Ni21+20%WC+0.5%CeO2熔覆层组织细小,高温干摩擦磨损性能最好。 相似文献
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三维图像多相分割的变分水平集方法 总被引:8,自引:1,他引:8
变分水平集方法是图像分割等领域出现的新的建模方法,借助多个水平集函数可有效地实现图像多相分割.但在区域/相的通用表达、不同区域内图像模型的表达、通用的能量函的设计、高维图像分割中的拓展研究等方面仍是图像处理的变分方法、水平集方法、偏微分方程方法等研究的热点问题.文中以三维图像为研究对象,系统地建立了一种新的三维图像多相分割的变分水平集方法.该方法用n-1个水平集函数划分n个区域,并基于Heaviside函数设汁出区域划分的通用的特征函数;其能量泛函包括通用的区域模型、边缘检测模型和水平集函数为符号距离函数的约束项3部分;最后,针对所得到的曲面演化方程,采用半隐式差分格式进行离散,并对多种类型三维图像进行分割验证了所提出模型的通用性和有效性. 相似文献
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The purpose of the investigation was to create a new gold alloy of yellow for casting the frames of metal ceramic dentures. The yellow color corresponds to the consumer and aesthetic needs of some patients, because it is a sign of the metal, which is noble and innocuous. The main alloying elements of the majority of gold alloys for metal-ceramics are platinum and palladium, which increase the strength characteristics. Copper, tin, and other precious metals and base metals are also introduced in these alloys. At the same time, it is necessary to ensure the correspondence of the properties of the alloy with those of the ceramics applied onto the metal frame. For this purpose, the thermal expansion coefficient of the alloy (TEC) should be in a range of 13.5~14.5 ×10 6 K 1 when heated from 20 to 600 ℃ . The two-component alloys, alloying of gold with platinum and palladium results in a decrease in the TEC, and the introduction of copper, silver, and tin, increases it. Multidirectional influence of the alloying elements is a factor in achieving compliance of the TEC with the given values of the alloy. In multicomponent systems, however, the mutual influence of individual components on the properties of the alloy is unpredictable. This also applies to the color characteristics of the alloys, which vary in the direction of reducing the yellowness with increasing concentration of platinum and palladium, while other elements may have the opposite effect on the results. Yellowness index (YI), calculated according to the results of spectrophotometric studies, has been chosen as an objective indicator of color. In this study, the requirement for YI was given not less than 25; the color of such alloys can be called light yellow. All the alloys investigated contained 85% (by weight) of gold. Therefore, higher corrosion resistance and biological inertness of a finished dental products were ensured. Among the alloys that met the yellowness/TEC requirements, two alloys have been selected that were "most yellow" (PLAGODENT-PLUS and PLAGODENT-BIO). Their adhesive properties met the requirements of GOST R 51736-2001 to alloys for metal ceramics. 相似文献
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本文主要介绍通信系统中低电压大电流电源设计所面临的稳压、散热、输入噪声和成本等方面的问题,分析多相技术、板上电源、同步整流和次级控制等新技术,并给出了一种低电压、大电流电源的设计文例。 相似文献
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本文首先阐述了自蔓延高温合成技术的发展和应用现状。其次,采用SHS技术在T10钢材表面合成了厚为10 mm的A12O3/Fe表面梯度复合层,分析出复合材料的成分呈梯度变化,金属陶瓷由陶瓷层逐步过渡到基体金属。同时,本文还研究了各添加剂元素对金属陶瓷结合等性能的影响规律。 相似文献
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