A Study of Some Factors Influencing the Wear Resistance of Lubricated Gold Contacts

Friction and wear tests have been performed on goldplated (2-3 m thick) contacts lubricated with three different lubricants: polyphenyl ether,perfiuorinated polyether, and microcrystalline wax. The lubricating properties were studied on gold coatings with a hardness varying between 80 and 200 Vicker\´s hardness number (VHN) and surface roughness between 0.05 and 0.15 mm center line average (CLA). The lubricants were tested both in unaged and aged conditions. The wear tests were chosen to simulate the action of different types of electrical contacts. The wear was estimated from observations in scanning electron microscopy (SEM) and worn surfaces were analyzed with energy dispersive X-ray analysis (EDAX) and Auger electron spectroscopy (AES). At low numbers of cycles (1-2.5-N load), wear could be correlated with the viscosity of the lubricants, while for longer runs (20 000 cycles) the creep rate of the Lubricants becomes important. At 100 000 cycles or more (0.25-N load) the gold coatings ona number of specimens were worn through either due to depletion of the lubricant, or when lubricant was still present in the wear track, simply due to the repeated minor wear, which occurs for each cycle during boundary lubrication conditions. Contact resistance, viscosity, and creep rate were measured for the three lubricants both in the initial condition and after prolonged exposure at elevated temperature and in an SO2atmosphere. The results are discussed in terms of practical recommendations for use of different lubricants on various types of separable electrical contacts