Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons

The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.     

Evaluation of Process Capability in Gas Carburizing Process to Achieve Quality through Limit Design Concept

NUMEROUS INDUSTRIAL APPLICATIONS requirea hard wear-resistant surface called the case,and arelatively soft,tough inside called the core.There arefive principal methods of case hardening:?Carburizing?Nitriding?Cyaniding or carbonitriding?Flame hardening?Induction hardeningThe first three methods change the chemicalcomposition,carburizing by the addition of carbon,nitriding by the addition of nitrogen and cyaniding bythe addition of both carbon and nitrogen.The last twomethods do n…     

Computer Simulation of the Process of Quenching Large-Size Parts in Water and Aqueous Solutions

DESPITE of the rapid development of computerfacilities and numerical methods of computing thestress-strain state of large-size parts,the accuracy ofcomputations is not sufficient because of the lack ofaccurate input data.For this reason,heat treatingengineers do not trust computations and are afraid ofquenching of large-size parts in water,in particular,when Bi—>°°.There are some causes of suchsituation:1)Because of inaccurate boundary conditions andincomplete information on mechanical p…     

多孔材料:现状和发展趋向

本文评论了近半个世纪以来有关多孔材料的现状和发展趋向。指出了利用多孔材料的孔隙度、孔径分布、渗透性及缓冲能力、毛细管引力、电阻、耐磨性、高的比表面及表面张力等性质,而在可渗透材料、轴承、蓄电池、燃料/空气电池、医学领域、密封圈、灯芯、发散冷却、振动缓冲、模的润滑、原子能工业等方面的应用。较为详细地叙述了多孔材料在过滤、轴承、碱性蓄电池电极板三方面的应用。同时也指出了多孔材料     

PROPERTIES, WELDABILITY AND APPLICATIONS OF ADVANCED WROUGHT SUPERALLOYS FOR GAS TURBINE ENGINES

Alloy selection and alloy design both require consideration of an array of material attributes, including in-service properties, weldability and fabricability. Critical properties of advanced wrought superaUoys for gas turbine applications include high temperature strength, thermal stability, oxidation resistance and fatigue resistance. In this paper, the properties of twelve wrought solid-solution-strengthened and six age-hardenable superalloys are compared. Weldability is an important attribute and can be a major limiting factor in the use of certain alloys. Weldability test methods are discussed and the resistance of alloys to solidification cracking and strain-age cracking is compared. The use of weldability testing in the development of modern wrought superalloys is discussed with several examples cited. Finally, alloy selection for gas turbine components is outlined, taking into account both alloy properties and fabricability.     

A302B类钢室温疲劳试样的断口组织照片和显微组织分析

<正> 本文通过对A302B类铁素体压力容器钢室温试验的试样显微镜分析,描述材料的断裂过程并确定它与疲劳裂纹扩展数据的关系。断裂试样用了扫描电镜(SEM)、电子照相技术和能散X射线显微分析作检查。对切自T-L方向的试样的断面所作的扫描电镜检查披露了存在着在所观察倒的ΔK临界值以上时夹杂物带。随后所进行的X射线影象扫描以及目对应的能谱表明带区是硫化锰夹杂。这些试样在夹杂物带区上的裂纹扩展速度与L-T向试样相仿。产生夹     

热载荷下A1203—球铁、ZrO2—A1—Si合金，以及ZrO2球铁热障涂层中热应力的产生的比较

表面处理技术如等离子喷涂、物理气相沉积、化学气相沉积已经被方便得用来制备用于高科技应用方面的复合涂层。高温涂层的目的主要有两点，第一是保护基体材料免受侵蚀，第二是提高耐磨性，另外对于热障涂层还有第三个功能就是使基体材料免受高温。在本研究中，用有限元方法对A1203—球铁、ZrO2—A1—Si合金，以及ZrO2球铁热障涂层在热载荷下的热应力产生和发展进行了分析，涂层与基体的厚度比为1／10，ZrO2球铁之间的梯度层为NiAl，NiCrAlY和NiCoCrAlY，这些因素都考虑到模型中去，计算了关键的界面区域(涂层/中间层/基体)的名义应力和剪切就布告并进进行了比较，结果表明ZrO2球铁的抗热冲击性能最好。此外，梯度层对热应力的产生程度有显著影响。本研究也表明，有限元方法可以用于优化陶瓷涂层的设计和生产。     

MODELING OF CONTROLLED THERMO-MECHANICAL PROCESSING OF TUBES FOR ENHANCED MANUFACTURING AND PERFORMANCE

1.IntroductionApproximately15milliontonsofsteeltubeandpipeproductsareconsumedintheUnitedStatesannually.Mechanicaltubesarethefeedstocksusedinthemanufactureofrollingelementbearings,hydrauliccylinders,alldagreatvarietyofpowertransmissioncomponents.Steeltubesarealsoemployedinthedrillstringsforoilandnaturalgasexplorationandrecovery.Steelpipesareusedinthetransportofgas,oilandotherfluids.ControlledThermal--MechanicalProcessing(CTMP)involvesprecisecontroloftemperature,mechanicaldeformation,andmicr…     

设计电解槽阳极时应考虑的因素

序言铝工业趋向采用低电流密度的大型多爪头阳极,所以考虑对使用中阳极有影响的起作用的机械应力和热应力的设计因素变得更加重要。设计时应该使合成应力不超过碳块的机械强度极限,同时要使钢爪和碳块间的接触电压降为最小。     

Ultra-low noise single-photon detector based on Si avalanche photodiode

We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5 Hz was achieved by cooling the photodiodes down to -80 °C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.