Three Regimes in the Tribo-Oxidation of High Purity Copper at Temperatures of up to 150 °C

November 02, 2022

Julia S. Rau (1), Oliver Schmidt (1), Reinhard Schneider (2), Rafaela Debastiani (3) (4), Christian Greiner (1)
Advanced Engineering Materials. Volume 24, Issue 11 (November 2022). DOI:


Surface oxidation of high-purity copper is accelerated under tribological loading. Tribo-oxide formation at room temperature is associated with diffusion processes along defects, such as dislocations or grain boundaries. Herein, the additional influence of temperature on the tribo-oxidation of copper is investigated. Dry, reciprocating sliding tests are performed with a variation of the sample temperature between 21 and 150 °C. Microstructural changes are monitored and analyzed with state-of-the-art electron microscopy techniques. Oxide layer formation through thermal oxidation is observed for 150 °C, but not for lower temperatures. As the temperature increases from room temperature up to 100 °C, a significantly stronger tribo-oxidation into deeper material layers and an increase in the amount of formed pores and oxides is detected. Up to 75 °C, diffusional processes of oxygen along grain boundaries and dislocation pipes are identified. Starting at 100 °C, CuO is detected. Hence, tribological loading significantly alters the CuO formation in comparison with static oxidation. Along with the CuO formation at temperatures ≥90 °C, the oxide layer thickness decreases while the friction coefficient increases. The observations broaden the understanding of the elementary mechanisms of tribo-oxidation in copper. Eventually, this will allow to systematically customize surfaces showing tribo-oxidation for specific tribological applications.

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Author Affiliation

(1) Institute for Applied Materials (IAM) and MicroTribology Center μTC, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
(2) Laboratory for Electron Microscopy (LEM), Karlsruhe Institute of Technology (KIT), Engesserstrasse 7, 76131 Karlsruhe, Germany
(3) Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
(4) Karlsruhe Nano Micro Facility (KNMFi), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany