An Effect of Co–W Barrier Sublayer on the Functional Characteristics of Au–Ru Contact Coatings

Abstract

The performance characteristics (microhardness, porosity, roughness, and transient resistance) of Au–Ru coatings with and without the Co–W alloy barrier sublayer electrodeposited on the surface of contact blades of commercially produced reed switches were investigated. It was found that the barrier sublayer reduces the average roughness of the coatings without significant change in their porosity. The Au–Ru coatings without sublayer exhibited a greater variation in the transient resistance during an increase in the pressing force. The service time of reed switches with the barrier sublayer increased in both testing modes: in low-power (50 mV, 5 μA, 50 Hz) by more than 4 × 106 switching cycles, and in mean-power (12 V, 0.25 A, 50 Hz) by more than 1.8 × 106 switching cycles.

Switching Properties of the Contact Coatings Based on Refractory Metals Alloys

“…The general form of R c (n) dependencies for all the samples studied is consistent with well-known concepts (for details, see, e.g., [2] and references cited therein). In each case, these dependences exhibit an initial descending part of a different duration mainly determined by the roughness of the initial surface and mechanical characteristics of the coating material [8,24]. A sharp increase in the R c -values observed in the final part of these dependencies indicates the beginning of the degradation of the contact surfaces.…”

“…Taking into account the shorter duration of the initial descending part of the R c (n) dependence (ca. 8 × 10 5 commutation cycles) and reliance on the results obtained in [8,23,24], it can be assumed that the microhardness, ductility, and surface roughness of this coating provides the most favorable friction/contiguity conditions of the contacting surfaces, which contributes to the formation and stability of an actual (conductive) contact area.…”

“…Information on the electrical properties of these coatings, in particular, on the contact electrical resistance, can be found in [3,4,23,24]. In [24], the Co-W alloy coating was employed as a technological sublayer under the main (working) Ru layer.…”

“…Information on the electrical properties of these coatings, in particular, on the contact electrical resistance, can be found in [3,4,23,24]. In [24], the Co-W alloy coating was employed as a technological sublayer under the main (working) Ru layer. The comparative study of the contact resistance of single-layer coatings based on Co-W, Ni-W, Co-Mo, and Ni-Mo alloys presented in [23] was shown that they are inferior to no other coatings based on the platinum group metals.…”