The Effect of Surface Preparation and Heat Treatment on the Interfacial Resistance, Friction, and Wear of Precious Metal Electrical Contact Alloys

The precious metal alloy couple (Pd-Ag-Cu-Au-Pt-Zn) with (Au-Cu-Pt-Ag-Zn) finds wide application as a wiping electrical contact. Experience at Sandia Laboratories in component applications has indicated that surface preparation methods can have a substantial effect on subsequent contact performance. Additionally, investigations have shown that the normally recommended heat treat process is in a time and temperature regime where alloy properties are rapidly changing. This can easily cause batch-to-batch variations in material properties such as microstructure, hardness, and bulk resistance. The effects of surface preparation and heat treatment on the contact resistance, friction, and wear of the alloy couple are investigated. Contact resistance was seen to be lowest and most stable when surfaces were either contaminated with small amounts of residual carbon, resulting from decomposition of organic contaminants during heat treatment, or were lapped to a matte surface. Very smooth surfaces exhibited erratic contact resistance and friction behavior. New heat treatment processes were found to provide an improvement in the friction and wear performance of this couple