DYNAMICS OF THE ELECTRODE PROCESSES ON THE REINFORCED MATERIALS AT HIGH-CURRENT IMPULSING DISCHARGE

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DYNAMICS OF THE ELECTRODE PROCESSES ON THE REINFORCED MATERIALS AT

HIGH-CURRENT IMPULSING DISCHARGE

A. Bushik

To cite this version:

A. Bushik. DYNAMICS OF THE ELECTRODE PROCESSES ON THE REINFORCED MATE- RIALS AT HIGH-CURRENT IMPULSING DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-467-C7-468. �10.1051/jphyscol:19797227�. �jpa-00219209�

JOURNAL DE PHYSIQUE CoZZoque C7, suppl6ment au n07, Tome 40, JuiZZet 1879, page C7- 467

DYNAMICS OF THE ELECTRODE PROCESSES ON THE REPEMICED MATERIALS AT HIW-CURRENT IMPUSING DISCHARGE

A.I. Bushik.

Physical Technical I n s t i t u t e o f the ByeZorussian, Academy o f Sciences, Minsk, U.S.S.R.

The f i e l d of composite m a t e r i a l s repre -

s e n t s a considerable source of p o s s i b i l i - t i e s fox searching erosion r e s i s t a n t elec- trodes. The experiments have shown t h a t er,osion r e s i s t a n c e of composite m a t e r i a l e l e c t r o d e s depends upon a chain l e n g t h of r e f r a c t o r y component s i n t e r e d p a r t i c l e s 1 t h a t i s , the longer these chains a r e , t h e more erosion r e s i s t a n t the m a t e r i a l is. It i s i n d i c a t i v e of perspective a p p l i c a t i o n

pe i n space and tLme which i s revealed i n appearance and existence of separate s p o t s pxoviding current flow through the boundary between metal and plasma. I n t h i s case the s p o t s on r e i n f o r c e d materi- a l s a r e of the same form a s on homogene- ous materials. However , t h e i r d i s t r i b u - t i o n due t o macroinhomogeneity of rein- forced m a t e r i a l s has a number of peculia- r i t i e s . As a whole discharge development of composite m a t e r i a l s with f i b r o u s struc-

twre, t h a t i s , reinforced materials. Spe- c i a l i n v e s t i g a t i o n of i n t e g r a l erosion e f f e c t a t discharge on the boundary l i n e between two metals have f i r s t been pre- sented i n 2 ^l I t has been shown t h a t i n t h i s case asymmetrical erosion t r a c e s form and the processes have been i n t e r p r e - t e d from the e l e c t r i c a l erosion migration theory point of view. Up t i l l now the dy- namics of t h e electrode processes on rein- forced m a t e r i a l s has not been i n v e s t i g a t e d

The electrode processes on reinforced ma- Fig. 1. E r o s i o n t r a c e on a r e i n - t e r i a l s : W-Ag, PJ-Cu, Fe-A1 a t discharges f o r c e d e l e c t r o d e i n t h e cathode regime with square c u r r e n t pulse of 1 8 0 , ~ s and ^{A )} Al-Fe; b) ?I-Ag

current amplitude of 450-1720 A have been occure during s e v e r a l s t a g e s , t h e i r du- s t u d i e d by high-speed photorecording. The r a t i o n depending on the m a t e r i a l composi- experiments have been c a r r i e d out i n a i r t i o n 3

.

fozced m a t e r i a l s i n cathode and anode ze- gimes a r e characterized by the presence of zones with continuous f a i l u r e of wires and bonds a s well a s the ones with f a i l u r e

discharge i n the cathode regime i s charac t e r i z e d by the developmen* of weak lumi- nescent mobile spots. The intense uniform luminescence of wires begins from about the 3 0 t h ps and ff om the 70th p s b r i g h t , of wires only along the perimeter. With l e s s mobile s p o t s appear. They develop

along the perimeters of the wires gradual- high density of wires the bond pressed

l y covering a l l t h e area with fur"cer out i n the form of l u g s i s observed t r a n s i t i o n t o the Al-bond. The regions (Fig. I a , b ) . of b r i g h t luminescent s p o t s form a b r i g h t Prom these photograms i t follows t h a t cloud i n the c e n t r e of the discharge, i t s

elect10de processes a r e of a d i s c r e t e ty- a r e a coinciding in dimensions with the

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797227

fused zone of the erosion trace. I n the case of the m a t e r i a l s \V-Cu and W-Ag the process of discharge development i s cha- r a c t e r i z e d by uniform luminescence of w i - r e s up t o 20-30 ps followed by the appea- rance of b r i g h t luminescent s p o t s along t h e perimeters of the wires which gradual- l y cover a l l the area of t h e wires with f u r t h e r t r a n s i t i o n t o the bond.

I r r e s p e c t i v e of the p o l a r i t y of e l e c t r o d e s and alongside with the s e l e c t i v i t y of spot appearance some delay i n appearing b r i g h t luminescent s p o t s i s observed i n compari- son with the case of homogeneous materi- als. The process of discharge fading i s characterized by fading f i r s t l y b r i g h t luminescent s p o t s on t h e bond and i n t h e c e n t r e of the wires. The s p o t s on t h e wime periphexy a r e the last t o disappear.

The reinforced m a t e r i a l s a r e charactefized by a b i g l e n g t h and random d i r e c t i o n of boundary l i n e s between metals with d i f f e - r e n t physical properties. T h i s i n f l u e n c e s the d i s t r i b u t i o n of spots 4 i n a compli- cated way. The r e f e a c t o r y wires a c t a s kerns s t a b i l i z i n g s p o t s a s i t happens i n t h e case of Hg-discharge.

Such a d i s t r i b u t i o n of s p o t s s u b s t a n t i a l l y influences t h e development of thermophysi- c a l processes which r e s u l t s i n a number of p e c u l i a r i t i e s of t h e erosion e f f e c t . The primary p e c u l i a r i t y c o n s i s t s i n the main heat l o a d being performed by the r e f r a c t o - r y wires of the wire f i t t i n g and a more f u s i b l e component performs the f u n c t i o n of a cooling agent. f he f u s i b l e component c o n t r i b u t i o n to t h e erosion process i s de- termined i n general by the vaporous phase because i t s melt i s kept from throwing out by the capkllary forces.

Hence i t follows t h a t the bond must pos- s e s s good e l e c t z i c a l and heat conductiv&- t y , a considefable wetting a s f a r a s the wire m a t e r i a l i s concerned, The b o i l i n g p o i n t i s t o be somewhat lower and compar- able With t h e melting temperature of the wires. The vapor pressure must be some- what l a r g e r than t h a t of t h e wire m a t e r i a l This w i l l condition discharge bwnSng on

the wires with smaller density of the cur- r e n t than i n the vapor of the wire materi- a l .

It i s a l s o important t h a t wire s i z e s sho- uld be comparable with the ones of heat i n t e r a c t i o n zone of metals. This w i l l pro- vide the l a r g e s t l e v e l l i n g of t h e heak load on the surface of the reinforced ma- t e r i a l . The delay i n appearance of b r i g h t s p o t s making the main c o n t r i b u t i o n t o the erosion i s deternXrzed by the cooling effect;

of the bond. The whole complex of the above conditions provides a considerable increa- se of the erosion r e s i s t a n c e of reinforced m a t e r i a l e l e c t r o d e s i n comparison with t h e ones of homogeneous materials.

R e f e r e n c e s

I. Rakhovsky V.I., Levchenko G.V., Teo- dorovich 0.K. , The Bzeak Contacti of E l e c t r i c a l Apparatas. Moscow, Energ.,

7966.

2. Nekrashevich I.G., Bakuto I . A . Izv.

AN BSSR, Ser. Fiz. Tekhn. Nauk, No.3, 1960,

3. NekrashevichI,G., BushikA.I., Ma- rek B.A. Sb. The High-Current Elect- r i c a l Contacts and Electrodes. Kiev, 1972.

4. Nekrashevich I . G b , Bushik A.I. Izv.

AN BSSR, Sex. Fiz.-Mat. Nauk No.6, 1971