Tribological and Thermal Properties of Mullite Coating Prepared by Atmospheric Plasma Spraying
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JTTEE5 23:410–419 DOI: 10.1007/s11666-013-0011-z 1059-9630/$19.00 ASM International
Tribological and Thermal Properties of Mullite Coating Prepared by Atmospheric Plasma Spraying Yulong An, Xiaoqin Zhao, Guoliang Hou, Huidi Zhou, Jie Chen, and Jianmin Chen (Submitted December 17, 2012; in revised form September 16, 2013) The primary mullitized andalusite powders were spray-dried and heat-treated to improve sprayable capability. Then, mullite coating was deposited by atmospheric plasma spraying and heat treatment was contributed to recrystallization of the amorphous phase present in the as-sprayed mullite coating. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phase composition of mullite coating. Meanwhile, the phase transition temperature, enthalpy, and specific heat capacity of as-sprayed coatings as well as recrystallized mullite coatings were determined by means of differential scanning calorimetry (DSC). Moreover, tribological properties of as-sprayed coating were investigated by SRV-IV friction and wear tester from 200 to 800 °C. It has been found that the as-sprayed coating possesses good thermal stability. DSC analysis reveals that recrystallization of the glassy phase present in the mullite coating occurs at about 980 °C. The friction coefficient of mullite coating was gradually increased from 0.82 at 200 °C to the highest value of 1.12 at 800 °C, while wear rates of the coating were at the order of 1025 mm3/Nm. The as-sprayed coating suffered the most severe wear at 800 °C. The observed wear mechanisms were mainly abrasive wear, brittle fracture, and pullingout of splats.
Keywords
atmospheric plasma spraying, friction and wear behavior, microstructure, mullite coating, thermal properties
1. Introduction Mullite, with a formula of Al4+2xSi2 2xO10 x, is a type of aluminosilicate minerals, and its composition may vary with varying x from 0.25 (3Al2O3Æ2SiO2) to 0.4 (2Al2O3Æ SiO2) (Ref 1, 2). The composition of 3Al2O3Æ2SiO2 is the only stable intermediate phase in the alumina-silica binary system (Ref 3). Mullite as one of the most important ceramic materials has been widely used in modern engineering industry. On one hand, it exhibits good corrosion stability, which makes mullite as a potential to be used as an environmental barrier coating (EBC) that can provide effective protection to metallic components working in harsh conditions involving high-temperature, acidic medium, steam medium, etc. For instance, mullite coatings are used in EBC systems of silicon-based ceramic matrix
Yulong An, Xiaoqin Zhao, Guoliang Hou, Huidi Zhou, and Jianmin Chen, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; and Jie Chen, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China and Graduate School, Chinese Academy of Sciences, Beijing 100049, China. Contact e-mail: [email protected].
410—Volume 23(3) Febru
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