Quasicrystalline materials, in particular Al-Cu-Fe alloys, demonstrate a unique combination of mechanical and tribological characteristics, which makes them promising for use as wear-resistant coatings. Plasma spraying in combination with laser remelting allows the formation of dense and adhesively strong coatings with a controlled microstructure. The purpose of this study is to investigate the effect of temperature on the tribological properties of quasicrystalline Al-Cu-Fe plasma coatings obtained by laser remelting.
Al-Cu-Fe plasma coatings were deposited on a steel substrate. After deposition, the coatings were laser remelted to improve their structure and increase adhesion to the substrate. Tribological tests were carried out in the temperature range from room temperature to 400 °C using a pin-on-disk tribometer. The coefficient of friction and wear rate were determined. The microstructure of the coatings was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD).
The present study aimed to evaluate the effect of temperature on the tribological behavior of a quasicrystalline (QC) Al–Cu–Fe coating obtained by plasma spraying after its laser beam treatment with surface melting. Laser treatment resulted in the formation of a more uniform, dense and durable microstructure, compared to the initial coating obtained only by spraying. Tribological tests were carried out under conditions of reciprocating motion with a high frequency in the temperature range from 25 to 650 °C. A significant effect of temperature on the friction characteristics of the coating was found.
The microstructure analysis showed that the wear mechanism of the melted CC coating undergoes changes: from abrasive at room temperature to adhesive at 400 °C and intense adhesive wear at 650 °C, caused by the transfer of material to the counterbody. In addition, it was found that the relative content of the icosahedral (i)-phase and β-Al50(Fe,Cu)50-phase in the coating after testing at 400 °C exceeds the same indicator at 650 °C. The change in the i/β ratio in the coating and the properties of the interacting bodies depending on the temperature are the key factors determining the wear mechanisms and the value of the friction coefficient.
The studies have shown that the friction coefficient and wear rate of Al-Cu-Fe plasma coatings obtained by laser remelting depend on temperature. With increasing temperature, a tendency to a decrease in the friction coefficient is observed, which may be due to the formation of oxide films on the friction surface, which have a lubricating effect. SEM analysis of worn surfaces revealed a change in the wear mechanism from abrasive at low temperatures to adhesive at high temperatures. X-ray diffraction confirmed the preservation of the quasi-crystalline phase in the coatings after tribological tests.
The results of this study allow us to conclude that the use of quasicrystalline plasma coatings of Al-Cu-Fe obtained by laser remelting is promising for wear protection under elevated temperature conditions. Further research is needed to optimize the composition and parameters of the coating formation process in order to improve their tribological characteristics over a wide temperature range.
Author: L.P. Feng, T.M. Shao, Y.J. Jin, E. Fleury, D.H. Kim, D.R. Chen
Institute: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, People’s Republic of China, Korea Institute of Science and Technology, Seoul, 130-650, Korea, Center for Non-Crystalline Materials, Yonsei University, Seoul 120-749, Korea