Effect Of Rare Earth Ce On Microstructu And Properties Of Super304H Steel

With the development of thermal power generation in China and the need for energy conservation and emission reduction,improving the efficiency of thermal power generation has become an important trend in China's future thermal power generation,and improving the efficiency of power generation is mainly achieved by improving the unit parameters(namely steam pressure and steam temperature).However,the service conditions of boiler steels in ultra-supercritical units are relatively harsh,requiring high oxidation resistance and thermal strength.Inner Mongolia is rich in rare earth.In this paper,the influence of rare earth on the mechanical properties and high-temperature corrosion resistance of heat-resistant steel was explored by adding rare earth Ce to Super304H steel.Super304H steel was tested by mechanical performance test and microstructure observation.The experimental steel was aged at 650?and 700?for 25 h,50 h,100 h,200 h and 500 h,and then the structure of the experimental steel was observed after polishing.At the same time,Raman spectroscopy is used to analyze the oxide layer after aging.Draw the following conclusions:The addition of rare earth in the experimental steel can greatly increase the impact resistance of Super304H steel.Compared with the experimental steel without rare earth,the impact resistance of Super304H steel is greatly increased.After adding rare earth to Super304H steel,it is found that the deformation activation energy is lower than that when no rare earth is added.The high temperature aging experiments were carried out on the experimental steels at different aging temperatures.When the aging temperature was low,the hardness of the test steels without rare earth increased gradually with the increase of aging time,while the hardness of the test steels with rare earth remained basically stable.When the aging temperature is high,the hardness of all the test steels decreases gradually with the increase of time,indicating that with the increase of aging temperature,the content of precipitate in the steel also decreases,and the hardness of Super304H decreases.After adding rare earth to Super304H steel,it can inhibit the continuous extension of defects in the steel and enhance the high temperature corrosion resistance and thermal strength of Super304H steel.Rare earths are added to the experimental steel.The rare earths mainly exist in the grain boundaries in the form of cerium oxide and cerium oxy sulfide in the steel,and the inclusions are mainly spherical.It shows that after adding rare earth to Super304H steel,the inclusions are refined and the performance of the steel is enhanced.When rare earth is added to Super304H steel,the grains are significantly refined,indicating that the addition of rare earths can significantly refine the grains and increase the performance of the steel.The oxide layer of 1#experimental steel is mainly Fe₃O₄with a small amount of FeO coexisting,while the oxide layer of 2#and 3#experimental steel is mainly FeO,and there is also the presence of Fe₃O₄.It shows that after adding rare earth to Super304H steel,the rare earth Ce in the steel hinders the further oxidation of the steel during the aging process.