Diffusion Behavior Of Carbide Forming Elements(Cr?Mo?W?V) In Alloy Steel Under High Magnetic Field

In the 21st century,the demand for clean renewable energy is becoming more and more urgent.Nuclear fusion and nuclear fission will replace traditional thermal power generation.Superconducting magnetic confinement Tokamak is the most effective way to achieve controlled thermonuclear fusion,such as ESAT in China.As an important structural material in the energy field,heat-resistant steel materials will face extreme conditions of ultra-high temperature and strong magnetic fields.This extreme condition can significantly change the service life of steel.The behavior of precipitation and evolution of alloy carbides is closely related to the diffusion of alloying elements.Therefore,the diffusion behavior of alloy carbide forming elements under the action of strong magnetic field and high temperature is studied.It has important theoretical guiding significance and potential practical application prospects for improving the service life and mechanical properties of heat-resistant steel under extreme conditions and developing new heat-resistant steel materials by using strong magnetic fields.In this paper,ternary heat-resistant steel(Fe-C-Cr,Fe-C-Mo,Fe-C-W)and quaternary heat-resistant steel(Fe-C-Cr-V)and high-purity metal elements(Cr,Mo,W,V)are experimental materials,which are made by diffusion bonding.The solid-state diffusion behavior of carbide forming elements(Cr,Mo,W,V)in different phase regions of heat-resistant steel under different magnetic field strength(0 T,6 T,12 T)was studied.And characterized by SEM,EPMA,mathematical simulation calculation and other means.The Boltzmann-Matano method is used to calculate the diffusion coefficient of each diffusion component in the diffusion couple with or without magnetic field.The results of solid diffusion behavior of Fe-C-Cr/C r diffusion couple under strong magnetic field show that the strong magnetic field promotes the mutual interaction of Fe and Cr atoms in the austenite phase region of Fe-C-Cr heat-resistant steel.The greater the magnetic field strength,the stronger the promotion.When annealing in the paramagnetic ferrite phase region,the strong magnetic field hinders the interdiffusion of Fe and Cr atoms.And the diffusion distance and diffusion coefficient of Cr atoms in the steel are significantly reduced.The greater the strength of the magnetic field,the stronger the blocking effect.In two different phase regions,the applied magnetic field has no significant effect on the phase composition and microstructure of the diffusion layer.The results of solid-state diffusion behavior of Fe-C-Mo/Mo diffusion couple under strong magnetic field show that the strong magnetic field promotes the mutual interaction of Fe and Mo atoms in the austenite phase region of Fe-C-Mo heat-resistant steel.diffusion.The greater the magnetic field strength,the stronger the promotion.When annealing in the paramagnetic ferrite phase region,the strong magnetic field hinders the interdiffusion of Fe and Mo atoms.And the diffusion distance and diffusion coefficient of Mo atoms in the steel are significantly reduced.The greater the strength of the magnetic field,the stronger the blocking effect.In two different phase regions,the applied magnetic field has no significant effect on the phase composition and microstructure of the diffusion layer.The results of solid-state diffusion behavior of Fe-CW/W diffusion couple under strong magnetic field show that the strong magnetic field promotes the interdiffusion of Fe and W atoms during annealing of the austenite phase region of Fe-CW/W heat-resistant steel.The diffusion distance and diffusion coefficient of W atoms in steel are significantly increased.The greater the magnetic field strength,the stronger the promotion.The applied magnetic field has no significant effect on the phase composition and microstructure of the diffusion layer.When annealing in the paramagnetic ferrite phase region,the strong magnetic field hinders the interdiffusion of Fe and W atoms,and the diffusion distance and diffusion coefficient of W atoms in steel are significantly reduced.The greater the strength of the magnetic field,the stronger the blocking effect.The application of the strengthening magnetic field did not significantly change the phase composition of the diffusion layer,but changed the microstructure of the diffusion layer,resulting in a significant increase in the number and size of the bulk WC particles.The results of solid-state diffusion behavior of Fe-C-Cr-V/V diffusion couple under strong magnetic field show that the applied magnetic field significantly hinders V during annealing of the austenite phase region of FeC-Cr-V heat-resistant steel.The greater the strength of the magnetic field,the stronger the blocking effect.The applied magnetic field significantly changes the phase composition and microscopic morphology of the diffusion layer.When the paramagnetic ferrite phase region of Fe-C-Cr-V heat-resistant steel is annealed,Fe,Cr,V atoms have no obvious interdiffusion.The application of a magnetic field suppresses the diffusion of C atoms.And the carbide diffusion layer is significantly reduced.