Enhancing the irradiation resistance of Cr coating via periodic insertion of nanochannel CrAlSiN layers that act as elastic unsaturated “sponges”

Cr-based coatings, as protective coatings of Zr-alloy fuel claddings, inevitably suffer from irradiation damage under actual nuclear operating conditions. Here, Cr/CrAlSiN multilayer coatings were deposited on Zircaloy substrates by magnetron sputtering, followed by the evaluation of irradiation resistance using Fe ions. The insertion of nanochannel-CrAlSiN layers refined the columns/grains in Cr layers and increased the interface density, contributing to the greatly enhanced irradiation tolerance and mechanical properties. A low average swelling rate of Cr layers was estimated to be ∼0.015 %/dpa after the irradiation of Fe ions at 400 °C. Moreover, the coating became compacted with strengthening columnar boundaries after low-dose irradiation (∼0.8 dpa). Both nanoindentation and micropillar compression test showed the transformation of the deformation mechanism for the multilayer coating, as the irradiated samples relieved stress mainly depending on the plastic deformation under loading, while many cracks formed in the as-deposited ones. Furthermore, in 1200 °C steam, a significantly thinner and denser oxide scale formed on the irradiated Cr/CrAlSiN coating, indicative of improved oxidation resistance. The mechanism of radiation-decelerated oxidation was briefly discussed.