Effect of lubrication on fretting wear and durability of gold coated electrical contacts under high frequency vibrations

Abstract

Electrical contacts are essential in many applications including modern transportation means such as airplanes, trains and automobiles as well as in everyday electronic portable devices. The mechanical components that form the electrical contact in these applications are always subjected to vibrations and micrometre displacements during use. These vibrations may lead to aggressive fretting wear, which in turn affects their durability. Most of the electrical connectors are coated with gold, thanks to the excellent electrical conductivity. One major drawback of using gold coating is its poor wear resistance. In order to improve the lifespan of such connectors, lubricating greases are considered to be a good choice. In this study, di-electric greases were tested to study their influence on improving the lifespan of automotive electrical connectors. The fretting behaviour was studied using a high frequency fretting tester and a high precision microtribometer. The electrical contacts were tested directly in their original design (male–female coupling) under small amplitude vibrations at a high frequency of 50 Hz. It is shown that dielectric greases do improve the electrical performance of the gold connectors by at least 25 times. The improvement is due to a reduction in wear loss and good isolation of the contact from ambient conditions thus preventing oxidation and third body abrasion. The usage of grease did not significantly affect the frictional aspect of the contact. Greases that hinder slip between the vibrating contacts were beneficial for the endurance of the connector assembly. Results indicate that simulation of electrical contacts by classical cross-cylinder configuration could yield different results from real insertion simulations thus challenging its credibility.