Quantitative Characterization of Carbide Loss and Correlation with Microstructure and Performance of Plasma-Sprayed NiCr-Cr3C2 Metal Carbide Coatings

Abstract

The aim of this work is to quantitatively describe the carbide loss during plasma deposition of metal carbide coatings and link it to the microstructure and performance of the as-sprayed coatings. To do this, a carbide loss index is defined. The results suggest that the microstructure and performance of such coatings can be tailored by controlling the content of carbides based on the proposed carbide loss index. The size of the particles in flight had the most significant effect on the carbide loss during the processing of the powder in the plasma jet. When the carbide loss index decreased from 0.028 to 0.014, the carbide content in the NiCr-Cr3C2 coating increased from 23.18 to 34.43 vol.%, effectively improving the microhardness of the coating and eliminating the formation of cluster cracks between the carbides and metal binder. In ball-on-disk friction testing with a Si3N4 ball, the coating with the highest content of carbides showed the lowest friction coefficient and best tribological properties. This study provides in-depth understanding of the nature of carbide loss and the factors that affect it under plasma spray conditions.