Laser clad surfaces for shark-skin effect by high-temperature activation

Embedding ceramic particles with a negative thermal expansion coefficient into a metallic corrosion resistant coating can establish a reversible thermal activation of a defined surface microstructure with the aim of having a shark-skin at high temperatures (in use) and self-cleaning at low temperatures (out of use). For that, CoNiCrAlY alloy is intermixed with yttrium and tungsten oxide as powder and then laser cladded onto a substrate. This coating is implanted with energetic ions in order to incubate the formation of Y2W3O12 which is a ceramic with strong negative thermal expansion. Such prepared coatings are then exposed to high temperature and the effects are investigated in detail. Results of phase formation, surface micro-morphology, microstructure and properties of the coatings are presented.