Microstructure and properties of plasma sprayed NbC-Al2O3 composite coatings.

Niobium carbide has received widespread attention due to its high melting point, high strength, high chemical stability and high wear resistance, but the current preparation of niobium carbide coatings using plasma spraying technology suffers from low deposition efficiency, poor fusibility of the composite powders, high porosity, and high defects in the coating microstructure. Therefore, the microstructure and properties of NbC-Al 2 O 3 composite coatings prepared by plasma spraying NbC-Al 2 O 3 -SiC composite powder and reactive plasma spraying Nb 2 O 5 -SiC-Al composite powder were comparatively investigated in this paper. The reaction mechanism of Nb 2 O 5 -SiC-Al composite powder during plasma spraying as well as the mechanism of the formation of coatings were analyzed in detail. The results showed that compared with the ex-situ NbC-Al 2 O 3 -SiC coating fabricated by plasma spraying, the in-situ Nb 2 O 5 -SiC-Al composite coating prepared by reactive plasma spraying had an obvious layer structure, low porosity (5.8 %), high hardness (1141 HV 0.1), high toughness (22.94 J/m2), and good scratch resistance properties. [ABSTRACT FROM AUTHOR]