Effect of Cr particle size on the development of a chromia scale on Ni-Cr composites

Abstract The nanocystalline Ni-base composites dispersing Cr particles in different size range were deliberately fabricated. It showed that the Cr content for chromia scale formation at 900 °C decreased from above 20 wt% required by the microparticle (~4 µm in size) dispersed composite to much lower values of 13 wt% and 7.8 wt% required by the composites dispersing submicron- (~0.8 µm) and nanoparticles (~25 nm), respectively. The particle size effect on oxidation, primarily resulting from the finer Cr dispersions which favor more ubiquitous chromia nucleation when oxidation starts, offers a guideline for designing and manufacturing low-Cr containing but oxidation-resistant alloys.