Spallation and transient oxide growth on PWA 1484 superalloy

Re-heating of the alumina-covered, low-sulfur alloy (0.2 ppmw) indicates that outward grain boundary diffusion of aluminum and tantalum occurs through the α-alumina but not nickel. Also, no new Ni-rich oxides reform confirming that they are indeed transient oxides formed during the initial stages of oxidation of the bare alloy.