Properties of plasma-sprayed bond coats

Increasing bond coat oxidation resistance has been clearly linked to increasing durability of the ceramic layer of thermal barrier coatings (TBCs), However, recent studies have shown that significant differences in TBC life can be achieved for different bond coats that exhibit little or no difference in oxidation behavior, These data suggest that bond coat properties other than oxidation resistance can also influence TBC life, Determination of which properties affect TBC life and how they do so could be valuable in designing new, more durable TBCs, This paper reviews the results of comparative studies of the properties of three bond coat compositions that have similar oxidation behavior but different TBC lives. An analysis of the properties indicates that the thermal cycle residual stress, calculated from the coefficient of thermal expansion and the stress relaxation behavior of the three alloys, is strongly correlated to the observed differences in TBC life.