It has long been known that the addition of so-called reactive elements, such as Y, to alloys forming chromia scales improves the protectiveness of those scales by reducing the rate of scale growth and by reducing the tendency of the scales to spall during thermal cycling. It has been suggested that reduced spallation might arise from better scale adherence or from improved resistance to fracture.In this study Ni-30Cr and Ni-30Cr-0.5Y alloy samples were oxidized at 1000°C in pure O2for various times, then were either furnace cooled to room temperature, or thermally cycled between 1000°C and different lower temperatures. Scale fracture events, which are detected by acoustic emission, were collected throughout the experiment. Anin situX-ray diffraction technique was used to measure the elastic strains in the oxide scales at the isothermal scale growth temperature and at several temperatures during cooling.These measurements found higher elastic strains in the Cr2O3scales, during both isothermal oxidation and cooling, but for fewer cracking events, on the yttrium-containing alloy than on Ni-30Cr. We infer that the addition of yttrium increased the adherence of the scale to the substrate, since the scale was able to withstand higher elastic stresses.