Effects of novel plasma spraying process on microstructure and mechanical properties of composite coatings

Supersonic Atmospheric Plasma Spraying (SAPS) is a commonly used technique in thermal spraying. Compared with other techniques, SAPS has the advantages of being high speed with low oxidation of sprayed particles. Hence, it is widely used in the preparation of composite coatings.

M_n+1AX_n ternary compounds (M is an early transition metal, A refers to an element of Group A, X is C or/and N, n = 1–3) have a layered structure with a low density, high elastic modulus and good conductivity. As a result, the M_n+1AX_n phase is a very promising ceramic reinforcement phase for metal matrix composites. However, there are relatively few studies on the preparation of Cr₂AlC reinforced composite coatings, and there are fewer studies dedicated to the SAPS preparation process of MAX phase reinforced composite coatings. To obtain better coating propertities, the most suitable Cr₂AlC content and the optimal spraying process need to further investigated.

“The MAX phase possesses properties that are different from other binary ceramics, allowing such ceramics to create stronger diffusion interfaces with metals and thus enhance the performance of the coatings,” explains senior author Yu Wenbo, a professor at the School of and Mechanical Electrical control Engineering at Beijing Jiaotong University. “Research on the process of preparing the coatings and the amount of Cr₂AlC content could be helpful to the application of other MAX phases in the field of plasma spray-prepared coatings.”

The researchers found that the lowest porosity and the highest hardness and adhesion strength could be obtained when the Ar gas flow rate is 125 L/min, the H₂ gas flow rate is 25 L/min, and the current is 385 A. When the mass fraction of Cr₂AlC is 15%, the composite coating exhibits strength, which is only slightly lower than the other coatings, and has better mechanical properties.

The findings are published in High-speed Railway.

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Contact the author: Wenbo Yu, a Center of Materials Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong University, Beijing 100044, China, E-mail address: wbyu@bjtu.edu.cn

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