Tribological Performance and Tribofilm Evolution of TiAl Matrix Composites with Silver and Titanium Diboride at Elevated
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JMEPEG https://doi.org/10.1007/s11665-020-04936-1
Tribological Performance and Tribofilm Evolution of TiAl Matrix Composites with Silver and Titanium Diboride at Elevated Temperatures Bin Chen, Zengshi Xu, Yi Liu, Bing Xue, and Weidong Ma (Submitted April 24, 2020; in revised form May 25, 2020) In order to understand the anti-friction and anti-wear mechanisms of silver (Ag) and titanium diboride (TiB2) at elevated temperatures, the tribological performance and tribofilm evolution of TiAl matrix composites with Ag and TiB2 (TATs) are studied from 200 to 800 °C. The results illustrate that TATs exhibit excellent friction-reducing and anti-wear properties, which are attributed to the self-adjusted synergistic effect of Ag and TiB2 in the wide temperature range. Besides, the testing temperatures have strong influence on the chemical structure and evolution of tribofilms. Within 400 °C, Ag migrates to worn surface and mixes with TiB2 to form the Ag-rich tribofilms. At 600 °C, the lubricating effect of Ag diminishes and the oxidation of TiB2 is limitation, hence there is no well-consolidated tribofilm on the worn surface. At 800 °C, Ag loses the lubricating capacity, while TiB2 completely oxidizes to form B2O3, resulting in the formation of B2O3-rich tribofilms. Keywords
friction and wear mechanisms, solid lubricants, TiAl matrix composites, tribological performance
1. Introduction TiAl alloys (Ts) have shown promising applications in modern engines because of their superior properties containing low density, high stiffness, high strength and creep resistance at high temperature, high dimensional and good environmental stability (Ref 1, 2). They have been widely used in manufacturing of machine components such as shaft bearing of gasturbine engines and aircraft gears. However, previous studies (Ref 3-5) pointed out that the main restrictions for their applications were high friction and poor wear resistance under severe conditions, which affected the service life and stability of whole equipment. Therefore, it is very necessary to seek effective methods and achieve excellent anti-friction and wearresistant properties. After decades of efforts, one solution is to develop the TiAl matrix self-lubricating composites with lubricants for improving tribological performance. Owing to its large diffusion coefficient and high mobility, silver (Ag) has become more favorable. Studies carried out on how the incorporation of Ag into TiAl matrix composites could enhance the friction and wear properties (Ref 6-10). Their results indicated that the incorporation of Ag distinctly improved the friction and wear Bin Chen and Zengshi Xu, Wuhan Institute of Marine Electric Propulsion, Wuhan 430064, China; and Wuhan Hydrogen Fuel Cell Engineering Research Center, Wuhan 430064, China; and Yi Liu, School of Mechanical and Electronic Engineering, Wuhan Donghu University, Wuhan 430212, China; and Bing Xue and Weidong Ma, Yellow River Conservancy Technical Institute, Kaifeng 475004, China. Contact e-mail: [email protected].
Journal of Materials Engi
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