Research On Preparation And Corrosion Properties Of Fe-Cr Alloys Based On Electrodeposition Technology

The steel materials used in the nuclear power field have been exposed to extreme environments such as high temperature,high pressure,corrosion and ion irradiation for a long time,and are prone to failure and destruction.The stability and reliability of materials are the primary conditions for ensuring the safe operation of nuclear power plants.Fe-Cr alloys,due to their excellent corrosion resistance and high strength and toughness,have attracted widespread attention from scholars at home and abroad.The development of new Fe-Cr alloys in the field of nuclear power applications has more research value.Aiming at the problems of poor anti-irradiation performance and unstable corrosion resistance of traditional coarse-grained iron-based alloys in the application of nuclear power plants,this paper prepares Fe-Cr alloys with different microstructures through co-deposition based on electrodeposition technology.The ion-implantation method was used to produce Fe-Cr alloy layer on the surface of the pre-deposited nanocrystalline iron by Cr implantation.The corrosion resistance of the Fe-Cr alloy layer prepared under the two methods was investigated.Based on the literature reading and experimental exploration,this project has carried out the following work:(1)Fe-Cr alloy films were prepared by a direct current electrodeposition method using a trivalent chromium salt electrolyte.The cyclic voltammetry test method was used to clarify the reaction process of electrodeposition,and the effects of deposition voltage and CrCl₃ salt concentration on the morphology,structure and composition of the alloys were revealed by XRD,SEM and AFM.The chemical composition of the surface passivation film was analyzed by XPS.The corrosion performance of Fe-Cr alloy was analyzed by Tafel polarization curve and AC impedance spectrum.The cyclic voltammetry test results show that the electrodeposition process mainly involves the reduction of Fe²⁺and Cr³⁺under the glycine complexation,accompanied by the hydrogen evolution reaction under high deposition voltage.The increase of CrCl₃ salt concentration will cause negative shifts of Fe and Cr reduction peaks.The results show that the deposition voltage will have a significant effect on the crystal structure,morphology and composition of the alloys.At a deposition voltage of 1.9 V,an amorphous Fe-Cr alloy with a smooth and dense surface can be prepared.The CrCl₃ salt concentration in the bath will also affect the surface of the alloy,and high CrCl₃concentration will cause the alloy surface to become rough or even cracked.The best process parameters are an electrodeposition voltage of 1.9 V and a CrCl₃ concentration of 0.3 mol/L,where the Cr concentration can reach 40%.Electrochemical test results show that the deposited alloys have the lowest Icorr of 1.209*10^-5 A/cm²,the most positive Ecorr of-0.463 V,and the largest Rp of 10258??cm² under the best process parameters.The XPS analysis results show that the passivation film is primarily composed of Cr₂O₃ and Cr O₃,which contribute to maintain excellent corrosion resistance.(2)Nanocrystalline Fe was prepared by electrodeposition,and the effect of deposition voltage on the structure,grain size,and corrosion properties of the deposited films was studied.The results show that:Fe prepared by electrodeposition is a nanocrystalline material,and the grain size ranges from 10 to 20 nm,and a high density of boundaries results in the reduction of the corrosion performance of nanocrystalline Fe.The ion implantation technology is used to implant Cr ions into the pure iron substrate to form Fe-Cr alloy layer on the surface of the substrate,which improves the corrosion resistance of the alloy.Ion implantation has a flattening effect on the surface cells produced by electrodeposition and improves the surface quality.However,excessively high ion implantation can cause micro-cracks on the surface.The optimal injection time is 10 min with implantation rate of3.965*10¹⁴ ions/cm²?min.Under this process,the alloy has the best corrosion performance.Its self-corrosion current density Icorr and self-corrosion potential Ecorr are 9.751*10^-5 A/cm²;and-1.016 V,respectively.