Editorial

Abstract

Thermal Barrier Coatings (TBCs) in current gas turbine engines routinely deliver metal tempera-ture reductions of 50 to 80°C under normal conditions and as much as 140°C temperature reduc-tions in hot spots (Ref 1). This temperature reduction can be used to lower metal component tem-peratures under constant operating conditions to achieve longer life, or to increase the performance of the engine through higher operating temperatures while maintaining constant life of the component, as indicated by the horizontal arrows in Fig. 1. A middle road of longer life and increased engine performance/efficiency is also possible. The choice of how to use the thermal benefits derived from TBCs is critical, especially if the intent is to follow the high economic pay-off path of increasing the operating temperatures to increase engine efficiency. In this case, large increases in operating temperature and engine efficiency are possible with the insulating capabil-ity of TBCs. The problem is that if the temperatures are increased to take full advantage of the TBC insulating ability, and a large frac-tion of the coating spalls, the remaining bare metallic component would be subjected to high temperatures and unacceptably rapid deg-radation (Fig. 1). Obviously, the risk of coating failure must be balanced against the benefit of coating use.