Effect of Laser Remelting on the Tribological Performance of Thermal Barrier Coatings

Abstract

Gas turbine's efficiency improves as operating temperature is increased. For this reason, metallic components used in turbine engines, for propulsion and power generation, are protected by thermal barrier coatings (TBC). Laser glazing has been used to enhance the oxidation and corrosion resistance of thermally sprayed TBC, but there is no information about the effect of this treatment on the tribological performance. ZrO2(CaO) top coat and NiAIMo bond coating were flame sprayed onto an AlSI 1045 carbon steel. The top coat was laser remelted and a densified ceramic layer was induced in the top surface of the ceramic coating. Both, the as sprayed and the laser remelted top coatings, were formed by cubic ZrO2 with some tetragonal precipitates. The grain size was reduced by the laser treatment. The mechanical properties and the local wear rate were evaluated by depth sensing indentation and scratch tests respectively. The nanoscale wear behaviour was always improved by the laser treatment.

Revestimentos para barreira térmica: evolução e perspectivas

“…As trincas são devidas às tensões residuais provocadas pela oxidação da camada de ligação metálica em altas temperaturas (formação e crescimento da TGO), devido à permeabilidade da camada cerâmica porosa, e às diferenças de expansão térmica cíclica (fadiga térmica no aquecimento e resfriamento dos componentes, durante o serviço), resultantes da diferença de cerca de 30 % no coeficiente de expansão térmica entre a zircônia parcialmente estabilizada e a camada de ligação metálica [2,3,4]. Diversas pesquisas têm sido realizadas na busca de solucionar estes problemas, envolvendo, inclusive, o conceito de revestimentos graduados [19,20], pré ou pós-tratamentos dos revestimentos [21,22,23] e adição de dopantes [24,25].…”