Influence of the Cooling Method of the Molten Pool on the Laminating Characteristics in Direct Metal Lamination by Using Arc Discharge

In this study, the MELCOR v1.8.6 code was utilized to perform an analysis of the in-vessel accident progression in VVER1000 reactor during the Station Black-Out (SBO) accident with and without external reactor vessel cooling (ERVC) strategy. The analysis presented the predictions of the main phenomena during the accident such as failure of fuel cladding, collapse of lower core support plate, relocation of core debris to lower plenum and mass of debris components in lower plenum, and provided comparisons between two cases in term of main parameters such as integrity time of reactor and structure components of molten pool. These parameters are very important inputs for further research on the application of external vessel cooling strategy for VVER1000 reactor.

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Research on Cooling Method in Surfacing Repair Process of Aero Compressor Blade

Mathematical Problems in Engineering ◽

10.1155/2020/1208313 ◽

2020 ◽

Vol 2020 ◽

pp. 1-19

Author(s):

Shijie Dai ◽

Miao Gong ◽

Liwen Wang ◽

Tao Wang

Keyword(s):

Heat Transfer ◽

Forced Convection ◽

Heat Sink ◽

Molten Pool ◽

Cooling Effect ◽

Modeling And Simulations ◽

Cooling Method ◽

Jet Impact ◽

Convection Cooling ◽

Vertical Jet

For the cooling method in surfacing repairing, most of the research focuses on the method based on the fixture structure. However, due to the low thermal conductivity and ultrathin alloy blade, the heat transfer speed from the molten pool to fixture is slow. When the heat is transferred to the fixture, most of the molten pool has solidified and absorbed or segregated out some impurities. Therefore, how to cool the welding area directly is more critical. For this reason, the thermal cycle characteristics of typical points of the blade and the heat transfer process of the key area of the fixture are analyzed, the original cooling time is calculated, and two innovative cooling methods based on lateral forced convection cooling and vertical jet impact forced convection cooling are proposed. For lateral forced cooling, with “AF-field” lateral convection cooling modeling, the cooling effects of characteristic points and sections under different flow velocities are calculated. For vertical jet impact cooling, the pressure, flow rate, and convective heat flux distribution on the wall under different impact heights and nozzle diameter are calculated. The influence of different inlet flow rates on cooling performance is influenced, based on the analysis results of impact modeling, the moving heat sink model is established, and the cooling effect under different heat sink-source distances is calculated. The heat transfer rules of two methods are analyzed in detail through modeling and simulations. The results show that both methods can improve the cooling effect and the vertical jet impact cooling method has an effect that is more obvious. When the nozzle radius is 2 mm, the impact height is 4d, the inlet flow velocity is 35 m/s, and the distance is 7 mm, and the cooling time under the vertical jet impact method is shortened by 12.5%, which can achieve better cooling effect. The experiment further validates the effectiveness of the modeling and simulations.

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Fabrication of Elbow Pipe by Direct Metal Lamination Using Arc Discharge While Maintaining the Molten Pool in a Horizontal Position

International Journal of Automation Technology ◽

10.20965/ijat.2010.p0422 ◽

2010 ◽

Vol 4 (5) ◽

pp. 422-431 ◽

Cited By ~ 2

Author(s):

Toshihito Kamioka ◽

◽

Syuhei Ishikawa ◽

Hiroyuki Sasahara

Keyword(s):

Layer Thickness ◽

Molten Pool ◽

Good Accuracy ◽

Arc Discharge ◽

Horizontal Position ◽

Bulk Materials ◽

Direct Fabrication ◽

Near Net Shape ◽

Metal Products ◽

The Relationship

Direct fabrication machines have recently been put to practical use for metal products. However, there have been some problems. The devices and usable materials are very expensive, there are limits to the materials, and the strength of the materials is inferior to that of bulk materials, among other problems. The present study aims at the development of a near net shape fabrication machine using an arc discharge that always keeps the molten pool horizontal during the accumulation of layers. This is in order to enable the fabrication of an overhanging shape with good accuracy. During the fabrication of the elbow shape, it is necessary to gradually change the torch velocity and the attitude of the molten pool. In this study, we tried to clarify the relationship between torch speed and layer thickness. Finally, the fabricated elbow tube is shown.

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Preparation and characterization of thin films of carbon nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136891 ◽

1995 ◽

Vol 53 ◽

pp. 104-105

Author(s):

L. Wan ◽

R. F. Egerton

Keyword(s):

Carbon Nitride ◽

Arc Discharge ◽

Ion Beam ◽

Chemical Vapor ◽

Reactive Sputtering ◽

Vacuum Arc ◽

Specimen Preparation ◽

Bonding Structure ◽

Electron Energy Loss

INTRODUCTION Recently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4 are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNX films deposited by two different methods.SPECIMEN PREPARATION Specimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.

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