Development of growth and thermal stresses in NiO scale on pure Ni: The metal nanocrystallization effect

Ni sheet samples with one side normally coarse-grained and the other side nano-grained have been prepared for two-sided oxidation deflection testing. The sample is sharply deflected during heating up to 800 °C in air, because of a significant nano-grain growth. Deflection also occurs during the subsequent isothermal oxidation and cooling, due to the difference in the development of the growth and thermal stresses in the thermally-grown NiO on the nanocrystalline Ni. The latter is interpreted based on the investigation of the Ni nanocrystallization effect on the evolution of the microstructure of the NiO scale with time.