Steam oxidation resistance of plasma sprayed chromium‐containing coatings at 1200 °C

Abstract

In order to improve the high‐temperature steam oxidation resistance of Zircaloy fuel claddings, chromium‐containing coatings (Cr3C2‐NiCr and NiCr) were deposited on a Zr‐4 substrate by air plasma spray. The steam oxidation resistance of the two coatings was evaluated at 1200 °C under atmospheric pressure. The weight changes, phase compositions, and microstructures of the coatings before and after the oxidation test of 1 h were characterized. Results revealed that the Cr3C2‐NiCr coating effectively protected Zr‐4 from oxidation. A protective Cr2O3 scale with a thickness of about 7 µm was formed on the surface of the Cr3C2‐NiCr coating after 1 h duration and the formed oxide layer was about 100 times thinner than that formed on the uncoated sample. A none protective oxide scale was formed on the surface of the NiCr coated Zr‐4 samples. Severe inter‐diffusion between the NiCr coating and the Zr‐4 substrate was observed. The oxidation mechanisms of the two types of chromium‐containing coatings were analyzed and compared in detail.