Correlation of radius of cathode spot of vacuum arc of metals on the size of generated droplets

The simple relation to estimate the cathode spot radius of a vacuum arc of pure metals is obtained. On its basis, is established between the cathode spot radius and the size of droplets generated by the cathode spot a correlation. This enables to find ways to reduce droplets in the plasma flow, which forms coatings by the vacuum electric arc method. The paper presents the results of experimental study of the droplet sizes depending on the vacuum arc current iд. The size and amount of the droplets on an area of 1 mm2 of the coating surface are determined using the ImageSP program. As the initial data, the microstructures of the coatings are used with an increase of: ç100, ç200, ç500, ç1000, ç1500. The droplets have been generated by a cathode spot of a vacuum arc for the alloy of the composition, at.%: 68Al–8Cr–4Nb–20Si. It is established that the number of droplets with a diameter of < 2 μm is generated most of all, and the number of droplets with a diameter > 10 μm is generated least of all. The number of generated droplets with a diameter from 2 to 10 μm slightly depends on the arc current iд. It is noted that the diameter of the alloy droplet is smaller than the diameter of the droplets generated by the cathode spot on its components due to the fact that the radius of the cathode spot on the alloy is smaller than the radius of the cathode spot on its pure components.

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Experimental Investigation of a Magnetically Balanced Arc in a Transverse Argon Flow

Journal of Engineering for Power ◽

10.1115/1.3678473 ◽

1966 ◽

Vol 88 (1) ◽

pp. 27-30 ◽

Cited By ~ 9

Author(s):

T. W. Myers ◽

C. N. McKinnon ◽

J. C. Lysen

Keyword(s):

Magnetic Field ◽

Experimental Study ◽

Atmospheric Pressure ◽

Gas Flow ◽

Electric Arc ◽

Test Apparatus ◽

Gas Velocity ◽

Argon Gas ◽

Argon Flow ◽

Arc Current

An experimental study of an electric arc in crossed convective and magnetic fields has been made. An electric arc was established across a rectangular test section through which argon gas was flowing at approximately atmospheric pressure and velocities up to 100 m/sec. Magnetic field strengths up to 3 webers/m2, oriented so that the Lorentz force opposed the convective force on the arc, were applied perpendicular to both the arc and the direction of the argon gas flow. The test apparatus and the procedure used to obtain the experimental relationship between the velocity of the argon flow and the balancing magnetic field are described. An analysis which assumed the magnetically balanced arc to be a gaseous cylinder positioned between the electrodes and with a diameter varying directly as the arc current satisfactorily explained the observed dependence of the balancing magnetic field on the gas velocity.

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Evolution of the Cathode Spot Distribution in an Axial Magnetic Field Controlled Vacuum Arc at Long Contact Gap

Plasma Physics and Technology Journal ◽

10.14311/ppt.2017.1.99 ◽

2017 ◽

Vol 4 (1) ◽

pp. 99-103

Author(s):

B. Tezenas du Montcel ◽

P. Chapelle ◽

A. Jardy ◽

C. Creusot

Keyword(s):

Magnetic Field ◽

High Speed ◽

Cathode Spot ◽

Axial Magnetic Field ◽

Processing Method ◽

Vacuum Arc ◽

Single Spot ◽

High Speed Video ◽

Video Images ◽

Arc Current

The distribution of cathode spots in a CuCr25 vacuum arc controlled by an axial magnetic field and ignited on the lateral surface of the cathode is investigated for long gap distances, from the processing of high-speed video images. The processing method includes also estimating the current carried by a single spot and reconstructing the distribution of the current density at the cathode. Various distributions depending partly on the arc current are described.

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Experimental study of cathode spot motion and burning voltage of low-current vacuum arc in magnetic field

IEEE Transactions on Plasma Science ◽

10.1109/tps.2005.856515 ◽

2005 ◽

Vol 33 (5) ◽

pp. 1553-1559 ◽

Cited By ~ 63

Author(s):

K.K. Zabello ◽

Y.A. Barinov ◽

A.M. Chaly ◽

A.A. Logatchev ◽

S.M. Shkol'nik

Keyword(s):

Magnetic Field ◽

Experimental Study ◽

Cathode Spot ◽

Vacuum Arc ◽

Burning Voltage ◽

Spot Motion

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Vacuum Arc Cathode Spot Characterization on Graphite Materials Using Field Emission Gun Scanning Electron Microscopy (FEGSEM)

Microscopy and Microanalysis ◽

10.1017/s1431927600013015 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1225-1226

Author(s):

M. Kandah ◽

J.-L. Meunier ◽

R. Gauvin

Keyword(s):

Heat Flux ◽

Field Emission ◽

Cathode Spot ◽

Ion Beam ◽

Deposition Process ◽

Vacuum Arc ◽

Carbon Ions ◽

Emission Mode ◽

Current Densities ◽

Arc Current

Vacuum arcs on graphite cathodes are currently used as sources of carbon ions for the production of diamond-like films in the arc ion-plating (AIP) deposition process. Emission from these cathode sources is concentrated in very localized “cathode spots” having typically 10 (i.m in diameter for graphite cathodes. These spots carry the totality of the arc current, the remaining of the surface being unaffected by the discharge. For electron emission falling in the thermo-field emission mode, extremely high current densities up to 108 -109 Am-2 are induced generating a high localized heat flux to the surface during the spot lifetime. On metallic electrodes, this strong heat flux generates localized surface melting during the microsecond scale spot lifetime. High localized plasma pressures (>10 Atm in the case of copper) were found to exist in the cathode spot volume, leading to the co-emission of micro-droplets of the liquid metal along with the ion beam.

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