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Tuesday, April 25, 2006 - 4:10 PM
BSC13.4

Brazing of Non-Metallic Materials with Assistance of High-Voltage Electric Field

V. Y. Kezik, n/a, Katzrin, Israel

    Effect of electric field on wetting and brazing of Sital-type glass-ceramic Termal-11 and combination of glass-ceramic with steel and Kovar was investigated at DC voltage in the range of 10-750 V. Ternary eutectic of Cu-Mn-Si having melting point of 1073 K (1472oF) was used as a filler metal for brazing in vacuum and in air.

    Negative electric potential was applied to the base material by a stainless steel electrode, and positive potential was applied to brazing filler metal by a needle-like tungsten electrode.

    Contact angles at different voltages, spreading area of the filler metal, microstructure and shear strength of brazed joints were measured, as well as, a behavior of the molten droplet at different ways of current application was also studied.

    Effect of ellectric field started to work from the voltage of 10-15 V, when contact angle was decreased from 160o to 90-100o. Active wetting and spreading of the filler metal droplet in vacuum has begun at 100 V, and maximal spreading was reached in the range of 400-500 V.

    Increasing of voltage from 50 V to 750 V resulted in the decrease of the contact angle on glass-ceramic from 80o to 38o in vacuum and from 74o to 29o in air, whereby the minimal contact angle 11o was reached at 350 V.

    Spreading area was also increased sharply from 150 mm2 to 650 mm2, as well as the work of adhesion – from 1.7 to 2.7 J/m2 at changing voltage from  50 V to 700 V.

    Optimal parameters of brazing are: temperature of 1123-1153 K (1562-1616oF) at DC voltage of 150 V.

    Tensile strength of brazed joints measured using standard butt specimens was 350-390 MPa (50-56 ksi) for the pair of Sital-Sital, and 175-218 MPa (25-32 ksi) for the pair of Sital-steel.

    Thus, high voltage eventually activates interaction between molten filler metal and non-metallic base materials during the brazing that can be used for manufacturing reliable brazed joints of ceramics or glass-ceramics with metals both in vacuum and in air without a protective atmosphere.


Summary: Effect of ellectric field started to work from the voltage of 10-15 V, when contact angle was decreased from 160o to 90-100o. Active wetting and spreading of the filler metal droplet in vacuum has begun at 100 V, and maximal spreading was reached in the range of 400-500 V. Increasing of voltage from 50 V to 750 V resulted in the decrease of the contact angle on glass-ceramic from 80o to 38o in vacuum and from 74o to 29o in air, whereby the minimal contact angle 11o was reached at 350 V. Spreading area was also increased sharply from 150 mm2 to 650 mm2, as well as the work of adhesion – from 1.7 to 2.7 J/m2 at changing voltage from 50 V to 700 V. Optimal parameters of brazing are: temperature of 1123-1153 K (1562-1616oF) at DC voltage of 150 V. Tensile strength of brazed joints measured using standard butt specimens was 350-390 MPa (50-56 ksi) for the pair of Sital-Sital, and 175-218 MPa (25-32 ksi) for the pair of Sital-steel. Thus, high voltage eventually activates interaction between molten filler metal and non-metallic base materials during the brazing that can be used for manufacturing reliable brazed joints of ceramics or glass-ceramics with metals both in vacuum and in air without a protective atmosphere.