Westinghouse Electric Corporation

Norman S Hoyer

Jere L McKee

Paul G Slade

Natraj C Iyer

Ram Kossowsky

Semahat D Sinharoy

A process of hot isostatic pressing of powders to form electrical contacts is characterized by the steps: (A) mixing powders, 1 in the Drawing, from metal containing powder or metal containing powder plus carbon powder, where at least one of Ag and Cu is present, (B) thermal cleaning treatment of the powder, 2 in the Drawing, (C) granulating the thermally treated powder, 3 in the Drawing, (D) uniaxially pressing the powders without heating, 5 in the Drawing, to provide a compact, (E) placing at least one compact in a pressure-transmitting, pressure-deformable container, 6 in the Drawing, and surrounding each compact with fine particles of a separating material, (F) evacuating air from the container, 7 in the Drawing, (G) sealing the compacts inside the container, 8 in the Drawing, (H) hot isostatic pressing, 9 in the Drawing, the compacts through the pressure transmitting material at a pressure from 352 kg/cm.sup.2 to 2,115 kg/cm.sup.2 and a temperature from 0.5.degree. C. to 100.degree. C. below the melting point of the lower melting powder constituent, to provide simultaneous hot-pressing and densification of the compacts, (I) gradually cooling and releasing the pressure on compacts, 10 in the Drawing, and (J) separating the compacts from the container, 11 in the Drawing, where there is no heating of the compacts in the process before step (H).

Hot isostatic pressing of high performance electrical components

An electrical contact material characterized by a pressed and sintered powder of silver composite with about 5 weight percent of graphite fibers.

Circuit breaker contact containing silver and graphite fibers

An electrical contact suitable for use in high-current switching or circuit breaking, comprising a mixture of silver or copper with an alloy of tungsten carbide and titanium carbide. The contact material preferably uses from about 10% to about 90% silver by weight, the remainder being (WTi)C alloy, and preferably the alloy component comprises from about 35% to about 50% of WC, the remainder of the alloy being TiC. The contact is preferably made by a powder metallurgical process, and provides not only good impact resistance, weld resistance and erosion resistance but, even more importantly, provides low contact resistance, i.e. low electrical resistance when current flows through the closed contacts even after repeated cycling, as shown by the low temperature rise of the contact in use.

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Mt. Lebanon, PA, United States of America

Norman S Hoyer