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Abstract: Cu–Cr–(Zr) alloys are becoming the materials of choice for components such as spot welding electrodes, heat exchangers, trolley wires, and thermonuclear reactor parts due to their high strength, excellent electrical and thermal conductivity, outstanding resistance to corrosion and good tribological properties. In some applications like electric railway wires and spot welding electrodes, the strength and wear resistance of these alloys are critical factors, and thus they should be improved further by any means. In recent years, they have been improved by applying simultaneously the grain refinement and aging techniques, and substantial improvement in both room temperature strength and wear resistance have been achieved. However, the operating temperature seems to be very crucial regarding especially their wear resistance. It is important to known that whether the gained properties at room temperature by grain refinement and aging could also be prevented at elevated temperatures. Thus wear resistance of Cu-0.7%Cr-0.07%Zr alloy in different microstructural conditions have been studied as a function of temperature. For grain refinement, high pressure torsion (HPT) was applied. This leads to the formation of an ultrafine grained structure (UFG) with a mean grain size of 155 nm, which brought about an substantial increase in both hardness and strength values. Aging also improved further these properties. The wear tests were performed at temperatures between 20ºC - 600ºC using a pinon-disc tribometer (UTS Tribometer T30MT) with a high temperature module. The worn surfaces of the samples were analyzed using SEM/EDX. In general, the wear rate increased with temperature, and a transition from mild to severe wear was detected above 400ºC in all states of the alloy. The reasons behind the changes in wear resistance depending on temperature have been investigated and discussedfor the first time the current study.

Keywords: High temperature tribology Cu-Cr-Zr alloy High pressure torsion Ultrafine-grained materials