Effect of environment and materials properties on the friction and wear behavior of precious metal electrical contact alloy couples

The friction and wear behavior of the gold-base (ASTM E541) and palladium-base (ASTM B540) alloy couple was investigated in three environments as a function of the metallurgical state of the alloys. The microstructures and hardnesses of the alloys were varied by age-hardening heat treatments and/or cold rolling. Friction and wear measurements were made with a pin-on-disc configuration with the palladium alloy serving as the pin and the gold alloy acting as the plate. The poorest friction performance was found in the helium environment where both magnitudes and break-in characteristics varied extensively. The friction coefficient varied from 0.25 to 2.0; the variation for a specific pin-plate material differences, except for cold-rolled plates which had the worst performance. The poor performance in helium is compared with improved performance in the oxygen containing atmospheres where friction coefficients ranged from 0.1 to 0.25. In oxygen containing environments, the break-in was minimal and reproducible.