Characteristics and strengthening mechanism of precipitated phase of a new type of pressure vessel steel 25CrMo3NiTiVNbZr
In order to further improve the room temperature mechanical properties of 25Cr3Mo3NiNbZr steel,composition optimization was carried out for it,and 25CrMo3NiTiVNbZr steel was designed and prepared.The room temperature mechanical properties,precipitated phase characteristics and strengthening mechanisms of the two experimental steels quenched at 1050℃ and tempered at 640℃ for 2 h were studied by means of field emission scanning electron microscopy(SEM),transmission electron microscopy(TEM),electron backscatter diffraction(EBSD)technique and tensile testing machines.The results show that the main precipitated phase in the 25Cr3Mo3NiNbZr steel is spindle-shaped Mo-rich M2C phase,with an average diameter of 18 nm.Finer M2C and MC carbides are precipitated in the 25CrMo3NiTiVNbZr steel,with an average diameter of 7.93 nm.The room temperature tensile strength of the 25CrMo3NiTiVNbZr steel reaches 1412 Mpa,and the yield strength reaches 1279 Mpa,which is 283 and 336 Mpa higher than the 25Cr3Mo3NiNbZr steel,respectively.Through theoretical calculations,the strengthening mechanisms of the both experimental steels at room temperature are mainly precipitation strengthening,grain refinement strengthening and dislocation strengthening.Among them,the dislocation strengthening increment and precipitation strengthening increment of the 25CrMo3NiTiVNbZr steel are significantly increased compared to the 25Cr3Mo3NiNbZr steel,with an increase of 174 and 205 Mpa,respectively.
25CrMo3NiTiVNbZr steelcomposition optimizationstrengthen the mechanismnano precipitation phase
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