The Hardness and Wear of Electrochemically Grown Tantalum Oxide

Abstract

ABSTRACTFor several metallic systems, including tantalum, barrier (non-porous) oxide layers up to 200 nm thick can be grown quickly and efficiently using electrochemical techniques. The thickness of the oxide layer has been found to be linearly proportional to the voltage applied during the electrochemical growth process. These oxides can cause a substantial increase in both the hardness and wear-resistance of the surface. Ex-situ Micro and Nano indentation testing of the Ta/ Ta2O5 system has clearly shown that the indentation hardness increases with oxide thickness, even for indentation depths much greater than the oxide thickness. AFM imaging of indentations and analysis of nanoindentation curves suggests this increased hardness is due to the oxide impeding the pile-up of material at the edges of the indentation, which changes the geometry of the contact. Tribometer testing of various oxide thicknesses has shown that the oxide plays a similar role in preventing wear, specifically by preventing the transfer of material between the two contacting bodies and spreading the load over a greater area. Thus, the electrochemical growth of Ta2O5 provides a convenient method for providing protective hard coatings.