Investigation on Tribological Properties of the Pre-oxidized Ti 2 AlN/TiAl Composite
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Investigation on Tribological Properties of the Pre-oxidized Ti2AlN/TiAl Composite Daqun Wang, Dongli Sun, Xiuli Han, Qing Wang, and Guangwei Wang (Submitted October 17, 2017; in revised form January 02, 2018) Different oxidation layers on the Ti2AlN/TiAl substrate which was fabricated by in situ synthesis were prepared through thermal oxidation process. The microstructure, phase identification and elements distribution of the oxidation layers were analyzed. The tribological performance of pre-oxidized composites against Si3N4 ball at 25 and 600 °C, as well as the effect of pre-oxidation layers on tribological performance was systematically investigated. The results show that, compared to Ti2AlN/TiAl, the pre-oxidized composites present more excellent tribological properties, especially the wear resistance at 600 °C. It is a significant finding that, different from severe abrasive wear and plastic deformation of Ti2AlN/TiAl, the tribo-films formed by the pre-oxidation layers on the worn surface of pre-oxidized composites weaken abrasive wear and suppress the development of plastic deformation to protect the underlying composite substrate from wear. Moreover, the stable cooperation on the interface between tribo-films and Si3N4 ball results in the relatively steady friction coefficient. Keywords
metallic matrix composite, oxidation, tribological property, wear mechanism
1. Introduction TiAl alloys that possess remarkable properties, such as low density, high specific modulus and strength, are considered to be a potential candidate for high-temperature structural materials used in turbine blades, turbocharger wheels or exhaust valves in aerospace and automotive industry (Ref 1-4). Over the last several decades, efforts on the improvement in their mechanical properties at room and elevated temperature have been made. The considerable advancements, to some extents, meet the requirements for some aerospace and automotive parts, such as exhaust valves and turbocharger wheels (Ref 59). Nevertheless, what should not be ignored is the sliding contact in their potential applications and several investigations indicate that the poor wear resistance of TiAl alloys limits further applications (Ref 10, 11). Furthermore, different from the considerable researches on mechanical properties, the study of their tribological properties has still been insufficient (Ref 12-14). Recently, researches on enhancing the tribological performance of TiAl alloys have been conducted, illustrating that introducing reinforced phase was an effective method. Yao et al. (Ref 15) investigated the tribological properties of TiB2/ TiAl composite, demonstrating that the anti-wear skeleton role of TiB2 effectively enhanced its wear resistance. Similar results were found by Cheng et al. (Ref 16): The wear resistance increased dramatically by in situ formation of TiB2 in Ti-46Al-
Daqun Wang, Dongli Sun, Xiuli Han, Qing Wang, and Guangwei Wang, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin
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