Study On Creep Property And Oxidation Behavior Of 9Cr-15Co-2W-1Mo Ferrite Creep-resistant Steels

With the continuous consumption of fossil fuels and increasingly serious environmental problems,most countries have taken corresponding measures to deal with the occurrence of such problems.Among them,improving energy efficiency is an effective method.At present,the world's major economies are actively studying and developing ultra-supercritical thermal power generation units with higher steam parameters.The key to the realization of this goal is to develop suitable heat-resistant steel.Compare with austenitic heat resistant steel,9¹2%Cr ferrite heat resistant steel has become the main alternative material for high temperature components in the next generation thermal power units due to its advantages of small thermal expansion coefficient,good thermal conductivity,good welding performance and high cost performance.However,the present ferritic heat resistant steel can't meet the higher steam parameters of the ultra-supercritical thermal power generating set,therefore,we designed a new type of 9%Cr ferritic heat resistant steel,and its oxidation resistance performance and creep resistance performance were studied.The conclusions are as follows:?1?The microstructure of experimental steel is delta-ferrite and tempering martensite after normalizing and tempering to heat treatment.During the creep process,the martensite structure recovered and the lath characteristics gradually disappeared.Use three methods to evaluate the experimental steel under the condition of 650?/100 MPa the long-term life of less than 10⁵ hs.?2?The experimental steel at 625?,650?,675?,700?under the condition of creep fracture mode is ductile fracture;Laves phase was precipitated in the creep process.The M₂₃C₆and MX phases are precipitated in heat treatment process,with small size and dispersed in the matrix.?3?At 650?in air oxidation,the steel surfaced Fe₂O₃,Al₂O₃,forming first oxide film,in a2130 h after the oxide film in the new material?Fe,Cr?₂ O₃.?4?In 650?,containing 20%H₂O air oxidation,the steel surface SiO₂,because of the experimental steel does't contain Si,Therefore,the oxidation mechanism remains to be further studied.