Effect of heat treatment on corrosion resistance of supersonic atmospheric plasma-sprayed Cr3C2-NiCr coating

Supersonic atmospheric plasma spraying (SAPS) is a newly developed technique in preparing high-performance Cr3C2-NiCr coatings with a high deposition efficiency. In this work, the effect of post-heat treatment on carbide precipitation and corrosion property of the SAPS Cr3C2-NiCr coatings was investigated. The results suggested that heat treatment induced the precipitation of secondary carbide grains, and the size of these carbides increased with the increasing heat treatment temperature. In addition, the self-corrosion current density of the coatings thermally treated at 500 degrees C was seven times smaller than that of the coating without heat treatment. The corrosion morphology showed that significant corrosion cracks were present on the as-sprayed coating. In contrast, the heat-treated coatings demonstrated small corrosion holes due to the formation of small corrosion galvanic cells between the precipitation of carbides and the substrate.