The microstructure evolution of VC coatings on AISI H13 and 9Cr18 steel by thermo-reactive deposition process

The microstructures of VC coatings on AISI H13 and 9Cr18 steel obtained by thermo-reactive deposition at 920 °C for 4 h were studied. The coating on AISI H13 was composed of equiaxed grains with an average size of 0.27 ± 0.12 μm; the coating on 9Cr18 was composed of elongated grains. The average size was 1.56 ± 0.54 μm in the direction parallel to coating/substrate interface and 0.69 ± 0.09 μm perpendicular to coating/substrate interface. The increase in grain size of the coating formed on 9Cr18 was caused by the poor-supplying of carbon atoms for the formation reaction of vanadium carbide. These tendencies of the formation of equiaxed and elongated grains were attributed to the high and low carbon activities in the substrates, respectively.