Preparation And Corrosion Resistance Of SiC Multilayer Thin Films On The Lead Cold Reactor Shell

15-15 Ti austenitic steel is the candidate cladding materialon lead-cooled fast reacto.To improve the corrosion resistance of 15-15 Ti austenitic steel in the reactor complex environment,theSiC thin film are prepared on it by the magnetron sputtering such as SiC/AlN bilayer films,SiC/TiN/Ti three thin films and?SiC/AlN?₂ multilayer films.The 15-15 Ti austenitic steelscoated and uncoatedare immersed in Pb-Bi alloy solutionof oxygen concentration 10^-6 wt.%and 10^-8 wt.%for 1000 hrsat 500?.By using XRD,AFM,FESEM,EDS and microhardness tester,the structure,morphology and composition of the thin films are analysed.The results show?1?SiC/AlN bilayer films,SiC/TiN/Ti three layer filmsand?SiC/AlN?₂ multilayer filmshave been deposited on the 15-15 Ti austenitic steel by magnetron sputtering methods.Three kinds of SiC thin films with different buffer layer are continuous dense and higher crystallinity.The film hardness of SiC/AlN double-layer films and SiC/TiN/Ti films is 12.6Gpa and 17.2Gpa respectively.?2?In the Pb-Bi alloy of oxygen concentration 10^-6 wt.%for 1000 hrsat 500?,the thickness of oxide layer on 15-15 Ti steel uncoated is 1.9 um.The outer oxide layer is Fe₃O₄,and the inner is Fe-Cr spinel oxides.However in the Pb-Bi alloy of oxygen concentration10^-8 wt.%for 1000 hrsat 500?,the thickness of oxide layeron 15-15 Ti steel is about600 nm,and it is Fe-Cr spinel oxides.?3?There is the Pb-Bi permeation on 15-15 Ti steel coated with SiC/AlNbilayer films in oxygen concentration of 10^-6 wt.%after1000 hrsat 500?,but the AlN films can prevent the Pb-Bi corrosion.When oxygen concentration is decreased to10^-8 wt.%,the SiC layer is permeated by Pb-Bi solution,moreover AlN layer is alsoinfiltrated about 100 nm byPb-Bi solution,finally,AlN film preventes the Pb-Bicorrosion,there is no corrosion oxide on15-15 Ti steel coated with SiC/AlNbilayer films.?4?15-15 Ti steelcoated with SiC/TiN/Tiis penetrated about 200nmin Pb-Bi solution of oxygen concentration 10^-6 wt.%after 1000 hrs at 500?,therefore,the corrosion resistance of SiC/AlN bilayer films in Pb-Bi solution is superior to thatof SiC/TiN/Tithree layer films.?5?Under the same experimental conditions,the corrosion resistance of?SiC/AlN?₂ multilayer films is superior to that of the SiC/AlN bilayer films.Compared with thecorrosion resistance of three kinds of films,?SiC/AlN?₂ multilayer filmsare the best,SiC/AlNbilayer filmsare second and theSiC/TiN/Ti three layer films are the worse.However,the three kinds of filmson15-15 Ti steel are good protective coating for Pb-Bi solution.The results provide the theoretical basis and experimental data for further improving the corrosion resistance of 15-15Ti cladding material in Pb-Bi solution.