Effect of steam-rich environments on the tribological performance of Cr2O3 coatings at high temperatures

Abstract

This study investigates the tribological performance of a chromium oxide (Cr₂O₃) coating sliding against Inconel 718 at room temperature and at 450 °C, both without steam and in a steam-rich environment. A custom setup was used to generate and apply superheated steam at 200 °C during reciprocating ball-on-flat sliding tests. Surface analyses were carried out using 3D laser microscopy, SEM, and Raman spectroscopy. The Cr₂O₃ coating showed high wear resistance under all test conditions, and only the Inconel 718 counterballs exhibited measurable wear. Under conditions without steam, increasing the temperature led to lower friction and wear, which is associated with the formation of an oxide-based layer formed from counterball debris. When steam was present, the effect depended on the temperature. At room temperature, steam condensed on the surface, reducing contact between the materials and contributing to lower friction and wear. At 450 °C, the steam did not condense and interfered with the formation of a uniform oxide-based layer. This resulted in higher friction and localized wear in exposed regions of the interface. These findings support the potential of Cr₂O₃ coatings for use in harsh environments, such as hydrogen-fueled gas turbines, where both high temperature and steam exposure are present.