Structural determination of wear debris generated from sliding wear tests on ceramic coatings using Raman microscopy

Abstract

In order to address the important interest in wear debris and associated wear mechanisms, we have studied a series of physical-vapor deposition ceramic hard coatings (CrN/NbN, CrN, NbN, TiAlN/VN, and TiCN) using a ball-on-disk sliding configuration against corundum. The debris generated were characterized using Raman microscopy to identify compounds, especially oxides, generated during the wear process to gain a better understanding of tribochemical reactions. The high spatial resolution (2 μm), sensitivity to structural changes, and nondestructive nature make this technique ideal for the study of such small amounts of wear debris. This article examines binary, multicomponent, multilayered, and superlatticecoatings. Under dry sliding conditions of 5 N normal load and 10 cm/s speed, titanium-based alloy coatings were found to provide TiO 2 (rutile) debris. However, the addition of thin layers of VN to the TiAlN system provided a lower friction coefficient, and much less debris through the possible formation of a lubricious surface oxide. CrN- and NbN-based coatings were also found to produce debris with Raman bands corresponding to oxides. Contact temperatures were also estimated by comparison of the tribochemical products generated during sliding wear with the formation temperatures of oxides detected from static oxidation.