High-Temperature Stress Measurements During the Oxidation of NiAl

The growth stresses in α-alumina scales growing on stoichiometric NiAlduring oxidation in air at 1100°C have been measured by two X-raydiffraction techniques: the classic rocking technique and a newly developedfixed-incidence multiplane (FIM) technique. The growth stresses were foundto be within the experimental uncertainty of the measurements, i.e., nearzero. Measurement of the residual stresses using an optical-fluorescencespectroscopy (OFS) technique in adherent regions of the scale, after coolingto room temperature, were consistent with the growth stresses having beennegligibly small. These measurements contrast with previous measurements ofgrowth stresses in α-alumina growing on Fe–Cr–Al alloys,using the FIM technique, which indicated compressive growth stresses on theorder of 1 GPa. Possible reasons for these differences are discussed.