Effects of temperature and microstructure on the triblogical properties of CoCrFeNiNbx eutectic high entropy alloys

This paper is aimed to evaluate the high temperature tribological behaviors of CoCrFeNiNbx eutectic high entropy alloys which would be highly-promising candidates for high-temperature applications. The effects of testing temperature and material structure on the friction and wear properties are investigated. The CoCrFeNiNbx alloys display a low harness decrement rate about 35% from room temperature to 1000 degrees C, indicating good softening resistance. The main wear mechanisms are abrasion wear at room temperature, change to adhesion wear at 400 degrees C, and translate into oxidation wear and mechanical wear over 600 degrees C. The wear rates increase from room temperature to 400 degrees C and decrease afterwards. The effects of material structure are dominated by the hardness of alloy, the content of chemically active Nb element and the structure of oxidized tribo-layer. The compact oxidized tribo-layers with excellent anti-wear properties are formed on the worn surface of CoCrFeNiNb0.65 and CoCrFeNiNb0.8 alloys at 800 degrees C, leading to extremely low wear rate. (C) 2018 Elsevier B.V. All rights reserved.