Sliding Wear of Inlay Clad Metals and Electrodeposited Cobalt-Gold

Abstract

Clacl noble metals are of interest for the contacts of electronic connectors,because they are often less expensive to fabricate than electroplates. A wear study was conducted with a number of inlay claddings of pure metals and alloys of palladium, gold, and silver. Hemispherically ended riders of solid gold and coated with electrodeposited cobalt-gold (0.2 percent Co) were mated to fiats in reciprocation. Coupons plated with cobalt-gold were used as controls. The solid gold riders and the clad metals were found to be significantly more prone to transfer and wear than electroplated cobalt-gold. The relative hardnesses of the metals on the members determined the direction of transfer, with the softer moving initially to the harder, although prows sometimes formed on the rider which reversed the direction of net metal movement. The sliding performance of combinations of contact materials can be ranked as follows: electrodeposited cobalt-gold versus itself (best), electrodeposited cobaltgold versus claddings, and solid gold versus claddings. The harder clad materials such as DG 60Pd40Ag (also called DG R156)---an alloy of gold, palladium, and silver with a graded composition, from a gold-rich (55-85 percent) surface to 60Pd40Ag in the body of the metai--60Pd40Ag, and 40Au36Pd24Ag were superior to those which were softer, like 70Au30Ag and 69Au25Ag6Pt. Clad palladium was also relatively poor. A polyphenyl ether fluid lubricant improved sliding significantly, with electroplated cobalt-gold against itself still the best material combination. The clad metals of this study may be satisfactory replacements for electrodeposited cobalt-gold in connector contacts provided the opposing member has a plated cobalt-gold finish and a good boundary lubricant is used.