Oxidation protection dynamics of NiAl droplet by inflight in-situ carbon deoxidation during atmospheric plasma spraying for high performance NiAl coatings
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY(2023)
摘要
The oxidation of the metallic particles in plasma spraying leads to poor inter-lamellar bonding and thereby lower corrosion and high temperature oxidation resistance. In this study, a novel approach is proposed to exclude the oxide of in-flight Ni-Al droplets by introducing diamond as a deoxidizer in Ni/Al powder during plasma spraying. NiAl coatings were deposited with Ni/Al/diamond composite powder prepared by mechanical alloying by at-mospheric plasma spraying at different spray distances to study the effect of the diamond addition on the oxidation behavior of in-flight droplets. The results show that the oxygen content in APS NiAl coating (3.23 wt%) was significantly reduced to 0.61 wt% by adding 2 wt% diamond to the Ni/Al powder. The measurement yields particle temperatures of higher than 2200 degrees C. Such high temperature contributes to the in-situ deoxidizing effect of C-containing droplets, resulting in oxide-free NiAl droplets for the deposition of the coating with low oxide content. This enhances both inter-lamellar cohesion and coating-substrate adhesion. Moreover, it was found that the size effect of a molten droplet on its oxidation kinetics significantly influences deoxidizing efficiency. Smaller particles require higher diamond content to ensure the in-flight deoxidizing to form oxide-free metal droplets. The result was further confirmed theoretically by numerical simulation. The present work provides a new approach to control the in-flight oxidation of metallic elements during plasma spraying, which has significant implications for the preparation of high-performance protective metallic coatings.
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关键词
Diamond,NiAl coatings,Atmospheric plasma spraying,Oxidation,In-situ deoxidizing effect
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