Changes

The addition of 30 wt% Pd increases the mechanical properties as well as theresistance of silver against the influence of sulfur and sulfur containingcompounds significantly ''(Tables 2.17 and 2.18)''.Alloys with 40-60 wt% Pd have an even higher resistance against silver sulfideformation. At these percentage ranges however the catalytic properties ofpalladium can influence the contact resistance behavior negatively. Theformability also decreases with increasing Pd contents.

AgPd alloys are hard, arc erosion resistant, and have a lower tendency towardsmaterial transfer under DC loads ''(Table 2.19)''. On the other hand the electricalconductivity is decreased at higher Pd contents. The ternary alloy AgPd30Cu5has an even higher hardness which makes it suitable for use in sliding contactsystems.

AgPd alloys are mostly used in relays for the switching of medium to higher loads(>60V, >2A) as shown in Table 2.20. Because of the high palladium price theseformerly solid contacts have been widely replaced by multi-layer designs suchas AgNi0.15 or AgNi10 with a thin Au surface layer. A broader field of applicationfor AgPd alloys remains in the wear resistant sliding contact systems.

Fig. 2.67:Strain hardeningof AgPd30 by cold working

Fig. 2.68:Strain hardeningof AgPd50 by cold working

Fig. 2.69:Strain hardeningof AgPd30Cu5by cold working

Fig. 2.70:Softening of AgPd30, AgPd50,and AgPd30Cu5 after annealing of 1 hrafter 80% cold working