Frictional properties of silver over-coated on surface textured tantalum interlayer at elevated temperatures

Surface textured tantalum interlayer is designed to improve the friction properties of silver at elevated temperatures. In this study, the textured dimples were fabricated on the tantalum coated steel by pulse laser and the Ag coatings were deposited on the textured Ta interlayer by DC magnetron sputtering. The friction properties of silver films on the textured tantalum interlayer were tested by rubbing against a Si3N4 ball on a ball-on-disk tribometer from 25 degrees C to 600 degrees C. The results show that the friction performance of silver at 200 degrees C, 400 degrees C, 600 degrees C is improved by the textured tantalum interlayer while the role of texture is not significant for friction reduction at room temperature. It is not found a consistent trend that point to the ability of texturing to reduce friction at elevated temperatures. At the temperature above 400 degrees C, the role of lubricant storage for texture is more dominant. The silver films deposited on the textured tantalum interlayer with the dimple density of 6% shows relatively stable and low friction coefficient (mu = 0.2) at 600 degrees C. The combination of Ta2O5 and silver clusters on the worn surface of Ag/textured Ta composite coating contributes to the low friction coefficient at elevated temperatures.