Preparation of thermal barrier coatings for gas turbine blades by EB-PVD

Thermal barrier coatings for gas turbine blades have been coated by the EB- PVD method. This paper will mainly focus on two aspects of thermal barrier coatings: (i) the formation mechanism of the initial cracks during thermal cycle process; and (ii) the thermal barrier effect. The microcracks were on ly discovered inside the ceramic top coat of the thermalcycled TBCs. SEM/ED S observations indicated that some different oxides exist at the point just below the cracks. It seems that the formation of initial cracks resulted f rom oxidation stress as well as thermal stress. A simulated test facility h as been designed to investigate the thermal barrier effect. Based on the he at transfer theory of one-dimensional steady-state heat conduction, the the rmal barrier effect (Delta T) of two-layer structure TBCs was theoretically and experimentally studied as a function of the thickness of the coatings, the thermal conductivity, lambda, and the temperatures of the operating co nditions. (C) 1998 Elsevier Science S.A. All rights reserved.