Дугостойкость на воздухе сплавов WС – Cr3С2 – Сu с бескаркасной упаковкой карбидов

Abstract

In this work, the arc resistance of electrical contacts of the compositions WC – Cu, Cr3C2 – Cu and WC – Cr3C2 – Cu (with a mass ratio of WC:Cr3C2 = 1:1) was studied in comparison with the industrial contact D30V70, and an analysis was made of the dependence of functional properties on the composition and contact structures. Experimental samples of electrical contacts were obtained by liquid-phase impregnation of non-compacted carbide powders with copper at low-frequency (~ 80 Hz) vibration of the crucible with alloy components for 10 min in a resistance furnace in an atmosphere of flowing argon. Prepared samples were tested using equipment that simulated the operation of an AC contactor (170 A, 50 V, 1000 – 10000 arcing cycles). Their functional properties (hardness, arc wear, contact resistance) have been studied. The evolution of the structure was studied using optical and electron microscopy. It is shown that alloys containing WC or WC + Cr3C2 have stable values of contact resistance (up to 10,000 arcing cycles). Alloy WC57Cu43 (wt. %) has the highest arc resistance, which is not only comparable with the industrial alloy, but also surpasses it in long-term tests, despite the lower content of the arc-resistant phase. In contacts of the Cr3C2 – Cu composition, the contact resistance increases and grows most sharply after 4000 arcing cycles. In contacts made of bicarbide alloy WC – Cr3C2 – Cu, the degree of increase in contact resistance is similar to the industrial alloy, but the average values are higher. The wear layers of monocarbide alloys are highly oxidized. In a bicarbide alloy, there is no oxygen in the composition of such a layer. The composition of this alloy is represented by solid solutions of metals and their carbides, and the structure is finely dispersed. The mechanisms of arc resistance in electrical contacts of various compositions are discussed.