High Temperature Steam Oxidation Behavior of Cr-coated Zr-4 Alloy Prepared by Multi-arc Ion Plating at 1000 and 1100 ℃
Cr-coated zirconium alloy cladding is an important method to improve the high temperature oxidation resistance of light water reactor fuel assembly.The high temperature oxidation behavior of Cr-coated Zr-4 alloys was studied in steam environment.The Cr-coated Zr-4 alloy samples were prepared by multi-arc ion plating process.High temperature oxidation experiments were carried out in 1000 and 1100 ℃ steam environment.The oxidation mass gain of the samples was obtained by a high precision balance,and the surface and cross-section micro-morphologies,element distribution,as well as phase and thickness of the Cr-Zr diffusion layer were analyzed by scanning electron microscope(SEM),energy dispersive spectroscope(EDS)and X-ray diffractometer(XRD).The results show that there are a large number of droplets of different sizes on the surface of the Cr-coated Zr-4 alloy samples prepared by multi-arc ion plating,and the Cr coating grows preferentially along the(110)crystal plane.The oxidation mass gain per unit area and time approximately follows a parabolic law.The oxidation rate at 1100 ℃ is significantly higher than that at 1000 ℃.At the same temperature,the oxidation rate of the Cr-coated Zr-4 alloy is lower than that of the uncoated Zr-4 alloy.After high temperature steam oxidation,whisker-like oxides are formed on the surface of the samples,and there are a large number of micro-pores between the oxides.After high temperature steam oxidation at 1100 ℃ for 3 and 4 h,the surface of the samples is oxidized to form worm-like agglomerates.The cross section of the samples has a layered structure,consisting of Cr2O3 layer,Cr coating,Cr-Zr diffusion layer,and α-Zr(O)layer(ZrO2 layer).However,the thickness of the surface Cr2O3 layer does not increase synchronously with the increase in the oxidation time,while the thickness of the Cr-Zr diffusion layer increases with the increase in the oxidation temperature and oxidation time,which has a linear relationship with the oxidation time.Therefore,the Cr-coated Zr-4 alloy prepared by multi-arc ion plating shows good resistance to high temperature steam oxidation at 1000 and 1100 ℃.
Cr-coated Zr-4 alloyhigh temperature steam oxidationoxidation rateCr-Zr diffusionmulti-arc ion plating