Deposition and characterization of nanostructured WC–Co coating

Nanostructured WC–Co coatings were prepared with the vacuum plasma spraying process. The microstructure of the as-prepared coatings was determined with SEM, TEM and XRD. The results show that the main structure of the coatings is composed of WC grains with a mean particle size of 35 nm, which have a similar grain size to the primary powders. However, in some regions, the grain size of WC is reduced to about 10 nm due to the melting of the WC–Co powders. In some regions, WC grains are completely melted forming an amorphous phase. In some regions, WC grains have grown to 100 nm; in other regions, the second recrystallization occurred, strip-shaped and square-shaped structures are formed, which are as large as 500 nm. The main phase of the as-prepared WC–Co coating is WC with minor phases of α-W2C, β-WC1-x, and W3Co3C. The hardness of the coating is about 18 Gpa with a wide distribution.