Effect of quenching temperature on microstructure,mechanical properties and low-cycle fatigue performance of 12Cr12Mo steel
Microstructure and mechanical properties of 12Cr12Mo steel for steam turbine blades after quenching at different temperatures and tempering at 680 ℃ were studied using optical microscope,scanning electron microscopy,X-ray diffraction,Brinell hardness tester and electronic universal testing machine.The low-cycle fatigue performance of the 12Cr12Mo steel after heat treatment by different processes was studied,and its life prediction model was established.The results show that with the increase of quenching temperature(940-1000 ℃),the austenite grain of the 12Cr12Mo steel continues to grow,the width of martensite lath gradually increases,more carbide particles are dissolved in the matrix,and the mechanical properties show a trend of first increasing and then decreasing.The microstructure of the 12Cr12Mo steel after quenching at 980 ℃ and tempering at 680 ℃ is the best,resulting in the best mechanical properties,maximum number of cyclic fractures,minimum ratcheting strain,and best low-cycle fatigue performance.After quenching at 1000 ℃ and tempering at 680 ℃,the 12Cr12Mo steel contains more amount of δ-ferrite leads to poor mechanical properties.When the stress ratio R=0.1,the low-cycle fatigue life prediction model for the 12Cr12Mo steel is:SeqN0.0134f=495.5072.
12Cr12Mo steelheat treatmentmicrostructuremechanical propertylow-cycle fatiguelife prediction model
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