Study on Long-term Water Corrosion Behaviors of Cr-coating on Zircaloy-4
Cr coating was prepared on the outer surface of the Zr-4 alloy by plasma enhanced physical vapor dep-osition technique.The corrosion resistance of Cr-coated Zr-4 alloy was studied in 360 ℃ high temperature and high pressure water for 300 days.The results show that the Cr-coating is dense and well combined with the sub-strate,and there are no cracks,holes and other defects on the coating.After 300 days of corrosion,an oxide layer of about 6 pm is formed on the surface of Zr-4,and the nano-scale ultra-thin Cr2 O3 passivation layer gen-erated on the surface of Cr-coating can prevent the diffusion of O atoms to the matrix,which greatly improves the corrosion resistance of zirconium cladding.At the same time,the Cr will be released in the form of HCrO4-in the neutral oxidizing water and after the corrosion test,the coating thickness will be reduced from the original 15 pm to 6.2 pm.The thickness of ZrO2 oxide layer generated at the interface between the coated zone and the uncoated zone of the half-coated Zr-4 tube is about 6.1 pm after the test,which is close to the thickness of the oxide layer of the uncoated Zr-4 tube.Therefore,there is no electrochemical accelerated corrosion between Cr and the substrate Zr-4.The corrosion hydrogen absorption of the Cr-coated sample is about 1/2 that of Zr-4 sample,and Cr coating obviously reduces the precipitation of hydride in cladding,which is beneficial to the improvement of the cladding performance.
Cr coatingZr-4 fuel cladding360 ℃ water corrosionhydrogen absorption
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