This paper presents recent developments in thermal spray coating technology for thermal power plants. As for thermal barrier coatings for gas turbines, to accommodate the high gas temperatures required to improve thermal efficiency, a new ceramic topcoat material with low conductivity was developed. As for wear-resistant coatings for boiler parts, a C-Cr-Fe alloy coating was developed that is lower in cost than conventional chromium carbide cermet. Field tests of boiler parts show that the erosion wear rates of these coatings are as good or better than that of conventional cermet.

Yttria stabilized zirconia particles are plasma sprayed on polished stainless steel substrate. Starting powders are fused and crushed powder, and hollow spherical powder. Four types of the splat morphology, which are splash, rugged, gravel mounted, and disk splats, are observed. Splash and disk splats are fully melted particles, but rugged and gravel mounted like splats are partially melted particles Gravel mounted like splat is observed from only hollow spherical powder, and disk splat is observed in the case of high substrate temperature. It is found that the ratio of splat morphology changes with spraying parameters. Porosity of the coating from fused and crushed powder is higher and Young's modulus of that is lower than that from hollow spherical powder. The ratio of rugged and gravel mounted splats affect porosity and Young's modulus. Adhesive strength increases with the increase in the ratio of disk splat. So, the coating properties are improved by controlling splat morphology. KEYWORDS: Splat Morphology, Partially Melted Particle, Disk Splat, Porosity, Young's Modulus, Adhesive Strength