Abstract
Metallic Cr and multilayer CrN/Cr coatings with a thickness of 2.5 µm were deposited onto E110 alloy by magnetron sputtering. Oxidation tests in air were performed at 1100 °C for 10–40 min. The gravimetric measurements showed better protective properties of multilayer CrN/Cr coatings in comparison with metallic Cr coating. Multilayer coating prevented fast Cr–Zr inter-diffusion by the formation of a ZrN layer beneath the coating. The appearance of ZrN is caused by interaction with nitrogen formed from the decomposition of CrN to Cr2N phases. Optical microscopy revealed a residual Cr layer for the multilayer CrN (0.25 µm)/Cr (0.25 µm) coating for all the oxidation periods. Additional in situ X-ray diffraction (XRD) studies of coated alloy during linear heating up to 1400 °C showed that the formation of the Cr2Zr phase in the case of multilayer coatings occurred at a higher (~150 °C) temperature compared to metallic Cr. Multilayer coatings can decrease the nitrogen effect for Zr alloy oxidation. Uniform and thinner oxide layers of Zr alloy were observed when the multilayer coatings were applied. The highest oxidation resistance belonged to the CrN/Cr coating with a multilayer step of 0.25 µm.
Highlights
Nowadays, a wide variety of materials have been studied as protective coatings on zirconium fuel claddings to improve its resistance under normal operation (~360 ◦C, 18.6 MPa) and design-based accident (DBA, up to 1200 ◦C) conditions
Cr–Zr inter-diffusion, while a chromium coating deposited on top of the multilayers can act as the main protective layer that prevents inward diffusion of oxygen to Zr alloy similar to single layer metallic Cr coatings
In situ X-ray diffraction (XRD) measurements were performed on E110 alloy with the metallic Cr and multilayer CrN/Cr-250 coatings during linear heating in vacuum from room temperature to 1400 ◦C (Figures 9 and 10)
Summary
A wide variety of materials have been studied as protective coatings on zirconium fuel claddings to improve its resistance under normal operation (~360 ◦C, 18.6 MPa) and design-based accident (DBA, up to 1200 ◦C) conditions. During oxidation, Cr coatings can be consumed by diffusion into Zr alloys with subsequent formation of an eutectic Cr–Zr phase with low melting temperature (~1332 ◦C). To improve the oxidation resistance of coated Zr alloys, especially under beyond DBA conditions, a new coating preventing Cr–Zr inter-diffusion should be developed. Cr–Zr inter-diffusion, while a chromium coating deposited on top of the multilayers can act as the main protective layer that prevents inward diffusion of oxygen to Zr alloy similar to single layer metallic Cr coatings. Oxidation behavior of the coatings was discussed based on the analysis of the samples after oxidation, and in situ XRD studies at high-temperature heating up to 1400 ◦C were performed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
