Study On Electrochemical Corrosion And Hydrogen Embrittlement Sensitivity Of FeCrMn_1.3NiAl_x High Entropy Alloy

As a new type of alloy,high entropy alloy has various excellent properties,such as high strength,high hardness,corrosion resistance,wear resistance and so on.It has great development prospects in petrochemical industry,aerospace,pipeline transportation and so on.Taking FeCrMn_1.3NiAl_xhigh entropy alloy as the research object,the law and mechanism of the effect of Al addition on its corrosion behavior were explored by electrochemical test.The effect of heat treatment time on hydrogen embrittlement sensitivity of FeCrMn_1.3NiAl_0.75high entropy alloy was investigated by means of hydrogen evolution and hydrogen osmotic kinetics parameters.In order to be used in the transportation pipeline in H₂S environment,the corrosion behavior,hydrogen embrittlement sensitivity and the influence of corrosion products on the above behavior of the alloy in H₂S environment are also studied,so as to provide theoretical guidance and data support for its further development and practical application.The main research progress is as follows:（1）With the increase of Al addition,the crystal structure of high entropy alloy changes from fcc to bcc,and finally evolves into Al-Ni-Mn as granular and belt b2phase,which is fine and evenly distributed in the Fe-Cr-Mn matrix of bcc structure.With the increase of Al addition,the corrosion current density of the alloy will increase.In the alloy system,although the Al₀、Al_0.25、Al_0.5samples have a low corrosion current density,due to the large difference between the two phases,it will lead to serious local corrosion,and the Al_0.75sample has a two-phase structure with similar electrochemical activity and uniform corrosion.（2）Aging heat treatment did not change the bcc+b2 structure of high entropy alloy,but changed the proportion of b2 phase in granular and belt phase.The granular phase has stronger hydrogen capture ability than the belt phase.In addition,the granular phase is small in size,has a larger critical saturated hydrogen concentration than the belt phase,and is evenly distributed on the matrix.Therefore,the T₃sample with more granular phase has the smaller hydrogen diffusion coefficient and hydrogen embrittlement sensitivity.（3）As the potential moves to the anode zone,a dense protective film is formed on the surface of the four samples and they enter the electrochemical passivation state.In addition,The corrosion products produced in H₂S environment prevent hydrogen atoms from entering the alloy and reduce the hydrogen diffusion coefficient of the alloy.Due to the higher Cr content in the corrosion products formed on the granular phase and the stronger ability to capture H,the sample containing the most granular phases for 3 hours of aging heat treatment is less sensitive to hydrogen embrittlement than other samples.