Preparation And Oxidation Resistance Of Cr/CrN Composite Coating On Zr-4 Alloy

After the Fukushima nuclear accident,the safety of nuclear fuel cladding materials has received extensive attention from scientific researchers.Zr alloy has the advantages of low neutron absorption cross-section and good thermal conductivity.It is the most commonly used cladding material.However,the texture of Zr alloy is relatively soft,and the wear resistance needs to be further improved under normal working conditions.Zr alloy will interact with water under accident conditions.Steam reaction can cause an explosion,and certain measures must be taken to improve the safety of Zr alloy under normal operating conditions and accident conditions.The preparation of protective coating on the surface of Zr alloy is one of the effective means to solve this problem.Therefore,in this thesis,the Zr alloy surface composite coating design and preparation,protection performance and protection mechanism integrated research,to prepare the Zr alloy surface ceramic/metal composite coating,so that the coating has a certain degree of wear resistance and better performance under normal conditions.While strong binding force,it shows excellent oxidation resistance under accident conditions,providing technical support for improving the safety of nuclear reactors.Firstly,a Cr coating was prepared on Zr-4 alloy by DC magnetron sputtering technology.According to high temperature oxidation experiment and hydrophilicity test,the optimal substrate treatment process of the coating was determined to be 100,400,1200,2000 grit sandpaper in sequence.Sand and grind the base around into a circular arc.When the sputtering pressure is 0.5 Pa and the deposition time is 90 min,the Cr coating has better oxidation resistance and adhesion.In addition,vacuum heat treatment after coating can significantly enhance the bond between the coating and the substrate.In order to further improve the wear resistance of the coating,a ceramic wear-resistant and anti-oxidation coating was prepared on the Cr coating of the optimal process,and the composite coating materials were screened,and it was determined that Cr N was prepared by radio frequency magnetron sputtering technology as the upper layer.Coating material.The effects of sputtering pressure and substrate bias on the wear resistance,adhesion and oxidation resistance of Cr/CrN composite coatings were studied.The results show that when the sputtering pressure is 1 Pa and the substrate bias voltage is-100 V,the overall performance of the composite coating is the best,the coating surface is flat,the roughness is low,and it has excellent oxidation resistance and wear resistance..Since the surface of Cr and Cr N will generate thin and dense Cr₂O₃ at high temperature,it prevents further penetration of O₂ and achieves strong oxidation resistance.In this paper,Cr/CrN composite coating was prepared on Zr alloy by DC and RF magnetron sputtering technology.The coating has not only good adhesion and wear resistance,but also excellent oxidation resistance,which provides a new idea for the preparation of accident resistant Zr alloy cladding coating.