Influence of humidity on the endurance of silver-plated electrical contacts subjected to fretting wear

The aim of this study is to investigate the effects of the relative humidity (RH) on the fretting wear rate and the Electrical Contact Resistance (ECR) of a silver plated electrical contact. The analyses show that an increase of RH tends to increase the ECR fretting endurance Nc related to the failure condition (ΔR > ΔRth = 4 mΩ). However, a discontinuous evolution is observed. Below a RH threshold, RH = 50%, the endurance increase is rather slow and can be related to a decrease of the friction work at the interface. Above RH = 50%, the high humidity conditions modify the rheological properties of the debris layer. The wear rate is becoming smaller and a larger wear volume is required to reach the ECR failure. This induces a fast linear increase of Nc. Whatever the wear processes, the investigation confirms that ECR failure is reached when the silver concentration in the inner part of the contact is becoming lower than [Ag]th = 5%.