Properties of Tungsten Coatings Deposited on Graphite by Vacuum Plasma Spraying Method

Tungsten coatings of 409 mu m (without an interlayer) and 378 mu m (with an interlayer) thickness were successfully deposited by the vacuum plasma spraying method on a graphite (CX-2320) substrate. An optimum coating procedure consisting of a sand blast and a pre-heating to increase the substrate wettability, and a post-heating to stabilize microstructures of the coating layer was developed for a good coating quality. The mechanical characteristics and microstructure of the tungsten coating layers were investigated using a Vickers hardness tester, FE-SEM, EDS, and XRD. It was shown that the Ti interlayer prevented the diffusion of carbon to the tungsten layer, thereby suppressing the formation of tungsten carbide. High heat load tests performed on the coating samples showed that pores grew and propagated in the coating layer but nor cracks nor signs of delamination were seen.at the bonding layer.