Surface modification of air plasma spraying WC–12%Co cermet coating by laser melting technique

• The surface of WC–12%Co cermet sprayed by air plasma spraying technique has been modified by using CO2-laser.
• All the inherent coating defects have been vanished and good surface properties were achieved.
• New phases were observed after the re-melting of surfaces which are discussed in detail.

Tungsten carbide cermet powder with 12%Co was deposited on stainless steel substrate by air plasma spraying method. Two types of coatings were produced i.e. thick (430 µm) and thin (260 µm) with varying porosity and splat morphology. The coated samples were treated with CO2 laser under the shroud of inert atmosphere. A series of experimentation was done in this regard, to optimize the laser parameters. The plasma sprayed coated surfaces were then laser treated on the same parameters. After laser melting the treated surfaces were characterized and compared with as-sprayed surfaces. It was observed that the thickness of the sprayed coatings affected the melt depth and the achieved microstructures. It was noted that phases like Co3W3C, Co3W9C4 and W were formed during the laser melting in both samples. The increase in hardness was attributed to the formation of these phases.