High temperature oxidation performance and thermal shock resistance of TiN/Cr-coated zirconium alloy cladding
In order to study the high temperature oxidation properties and thermal shock resistance of TiN/Cr-coat-ed zirconium alloys,TiN/Cr-coated zirconium alloy samples were prepared by magnetron sputtering.High tempera-ture oxidation and thermal shock resistance experiments were carried out respectively,and the microstructure,phase and adhesion strength of the samples after high temperature oxidation and thermal shock resistance were characterized.The results show that there is a clear boundary between the TiN/Cr double-layer coatings prepared by magnetron sputtering,and there are round-like agglomeration protrusions on the surface of the samples,but the coating structure is dense and free of defects such as cracks and pores.After high-temperature oxidation,the sur-face Cr coating is partially oxidized to Cr2O3,which is an irregular polyhedral structure.Ti atoms from the TiN coat-ing diffuse to the surface and combine with O to form TiO2,which is a long-striped structure.The Cr2O3 aggrega-tion area is bubbling.At the interface between the coating and the substrate,the in-diffused Cr atoms and the out-diffused Zr atoms form a Cr-Zr diffusion layer with a thickness of about 5 pm.At the same time,O atoms continue to difuse into the sample and combine with Zr atoms to form ZrO2.Although the oxidation weight gain of the TiN/Cr coated zirconium alloy is smaller than that of the uncoated zirconium alloy,and the sample remains relative-ly intact,the internal zirconium alloy is oxidized due to the continuous diffusion of O atoms,indicating that the TiN/Cr coating cannot provide good long-term high temperature oxidation resistance for zirconium alloy.After the thermal shock test,the surface coating still completely covers the entire sample,but there is a molten pool-like area on the surface of the sample,accompanied by microcracks and pores,and the adhesion strength of the coating film/substrate is significantly reduced.
TiN/Cr-coated zirconium alloymagnetron sputteringhigh temperature oxidation performancether-mal shock resistancediffusion
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