共查询到20条相似文献,搜索用时 62 毫秒
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传统的渗碳后淬火+低温回火方法处理20CrMo齿轮材料会产生较大的应力和变形,将对齿轮的质量产生极为不利的影响.采用脉冲激光束对渗碳后的20CrMo合金进行表面强化,并与传统的渗碳后淬火+低温回火的处理方式进行了对比.结果表明:20CrMo合金钢在激光熔凝作用下表层产生了致密的硬化层,且激光照射能量越大,硬化层越厚,硬化深度最大可达到0.35 mm;与渗碳后淬火+回火处理的试样相比,激光束照射虽然使表面粗糙度上升,但是表面硬度可提高75%,摩擦系数和磨损量均较低,有效改善了其表面的耐磨性. 相似文献
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利用等离子束对球墨铸铁进行表面熔凝和表面合金化强化处理。采用扫描电镜、X射线衍射仪、硬度计、电化学工作站和磨损试验机等设备对强化层的组织、性能进行测试。结果表明:等离子束表面强化处理后,球墨铸铁表面石墨相完全消失,形成的改性层显微组织主要是枝晶结构;改性层的硬度最高值出现在次表层,熔凝层的最高硬度为1243HV0.1,合金化层的最高硬度达1343HV0.1;熔凝层和合金化层的耐蚀性和耐磨性相对于基体来说有很大的提高,并且由于合金化层具有更多的碳化物,组织更加致密均匀,其耐蚀性和耐磨性明显好于熔凝层。 相似文献
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纯钛铸件进行等离子渗氮、脉冲真空电弧离子镀TiN薄膜复合处理后,扫描电镜观察表面形貌,显微硬度仪测量硬度,球盘磨擦实验评估耐磨性。结果显示钛铸件渗氮、TiN镀膜复合处理后,表面呈现均匀明亮的金黄色,显微硬度和耐磨性均显著提高,且优于单纯镀TiN膜的钛铸件。此方法应用于口腔医学领域,对义齿钛支架进行表面改性处理,可提高其磨擦学性能,改善颜色。 相似文献
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强流脉冲离子束辐照对M2高速钢的表面改性 总被引:2,自引:0,他引:2
研究了强流脉冲离子束辐照对M2高速钢(W6M05Cr4V2)表面的微观组织和硬度的影响.结果表明,HIPIB辐照处理使高速钢样品表面强烈加热又快速冷却,产生表面淬火作用,导致碳化物溶解,马氏体溶碳量增大且晶粒细化或晶格畸变度增大,晶间出现残余奥氏体.辐照还使表面产生宏观残余压应力,形成一些弥散分布的火山口状熔坑.随着脉冲次数的增加,在材料表面产生微区光化现象,材料表面化学成分和相组成的差异、杂质分布以及位错密度不均匀性导致的非均匀、非稳定熔化等是产生熔坑的主要原因.辐照使材料表层及以下近200μm范围内的硬度提高,并出现硬度双峰现象,离子束辐照产生的应力波及其在材料中的传播所导致的位错密度增大是硬度提高的原因. 相似文献
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以TiC-TiB2复合材料为电极,采用电火花表面强化技术,在40Cr钢表面制备出TiC-TiB2复合强化层。利用SEM和XRD分析了强化层的微观结构和物相,测试了强化层的硬度和耐磨性,并探讨了其磨损机理。结果表明:强化层物相主要为TiB2、TiC和Fe3C等,非晶组织和组织细化使其衍射峰宽化;强化层的显微硬度分布呈梯度变化,最高硬度值是基体硬度值的4倍多;强化层中的硬质相和较高的显微硬度改变了试样间的磨损机制,强化层的磨损机制为显微切削、划擦和疲劳磨损;强化层的耐磨性比基体提高了约5倍,摩擦系数比基体低0.12~0.17。 相似文献
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为了提高Ti6Al4V钛合金的高温耐磨特性,在Ti6Al4V钛合金表面利用激光沉积制造原位生成TiC颗粒增强相的方法制备了钛基梯度涂层。观察了耐磨梯度涂层的微观组织,测量了涂层和Ti6Al4V基材在500℃条件下的摩擦磨损性能及其显微硬度,并对涂层的强化机制和磨损机理进行了分析。结果表明,原位自生的TiC颗粒增强相均匀弥散分布在基体中,从基材到涂层顶部分别呈现粗大树枝晶、较大的颗粒状晶体、相对细小的颗粒状晶体形态。显微硬度分析显示涂层硬度保持在400~450HV之间,由基材到表层呈梯度上升趋势。涂层表现出较好的高温耐磨特性,和基材的磨损体积比为2.86。TiC颗粒的弥散分布强化和激光沉积基体组织的细晶强化是显微硬度和高温耐磨性提高的主要原因。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献
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《中国标准化(英文版)》2014,(4)
正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from 相似文献
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《中国标准化(英文版)》2014,(5)
正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively. 相似文献