On the rumpling mechanism in nickel-aluminide coatings. Part II: characterization of surface undulations and bond coat swelling

A quantitative characterization of the surface morphology of platinum-modified nickel aluminide bond coats that develops in the course of cyclic and isothermal oxidation at 1150 deg C is presented. The amplitude and wavelength of surface undulations and their evolution with oxidation time are evaluated. Surface roughening (rumpling) is accompanied by swelling of the bond coat, especially during the initial stages of oxidation. The experimental results indicate that the two processes may be related and a possible link between rumpling and swelling is suggested. It is expected that the data will be useful in developing refined models of rumpling. (Substrate: nickel base superalloy.)