Gaseous contaminants modify the friction and wear response of precious metal electrical contact alloys

An in situ electrical contact resistance and friction coefficient measuring device has been installed in a scanning Auger microprobe. A pin-on-plate experimental configuration is used. This tribology system has been used to characterize the friction, wear, and electrical contact resistance of a Pd-alloy pin (ASTM B540) sliding on an Au-alloy plate (ASTM B541). Studies, with and without H/sub 2/S in the atmosphere, of wear in 1.6*10/sup -6/-Torr O/sub 2/, 700-Torr 5% O/sub 2/ in N/sub 2/, and 700-Torr He are reported. The presence of H/sub 2/S reduces the friction coefficient and decreases the wear track width on the Au alloy. The lower friction is associated with absorption and reaction of the H/sub 2/S with the Au-alloy plate. In the ambients containing H/sub 2/S, large accumulations of S in wear tracks are observed; however, no increase in the electrical contact resistance occurs. In the 700-Torr ambients containing H/sub 2/S, Cu segregates to the wear track surfaces to the exclusion of other metallic elements and forms Cu/sub 2/S layers. A concomitant shift occurs in the S and Cu Auger peak positions when the Cu/sub 2/S film thickens.<
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