Reactive plasma spray (RPS) is the promising solution among the thermal spray techniques to fabricate nitride coatings. It is a processing method which combines the in-situ synthesis and deposition of reaction products. Generally the RPS process depends on the reaction of the molten or semi-molten particles with the surrounding active species in the plasma jet followed by the deposition of the nitride coatings. Reactive plasma spray process was suitable technology to fabricate the aluminium nitride (AIN) coatings. This paper will discuss the influence of the particle diagnostics during reactive plasma spray process and as well as the properties of the fabricated AIN coatings as function of plasma gases. The N_2 gas flow rate increased the particles' velocity (reduced the particles residence time in the plasma), and thereby affected its melting, nitriding conversion, phase transformation, deposition efficiency and the coating thickness. Using H_2 gas with low flow rate is better for RPS of the fine Al_2O_3/AIN mixture. The H_2 gas flow increased the in-flight temperature and affected the in-flight vaporization, AIN content, phase transformation, deposition efficiency and the thickness of the coatings.
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