With the soaring prices of Ni and Mo,it is necessary to develop new high-performance and Ni-and Mo-saving stainless steel.Based on the composition of the S32654,a new type of super austenitic stainless steel(SASS)with 24.5％Cr-17％Ni-5％Mn-6.3％Mo-0.7％N was prepared by pressure metallurgy and element synergistic control methods.The precipitation behavior and mechanical properties of the steel were studied.The results indicate that during isothermal aging at 800-1 050 ℃,as the temperature increased,the cellar precipitates composed of Cr2N and σ phases first increased and then decreased,and 900 ℃ was confirmed to be the precipitation nose temperature of the steel.The ultimate tensile strength(UTS),yield strength(YS)and elongation of solid solution sample(1 200 ℃-30 min)can reach 958 MPa,517 MPa and 77.4％.With the prolongation of aging time at 900 ℃,the cellular precipitates underwent nucleation and growth,which promoted intergranular cracking,resulting in a decrease in UTS and elongation(797 MPa and 13％,respectively,after aging for 120 min),and the yield strength(YS)first decreased and then increased.After 5 min of aging,the formation of intergranular precipitates consumed solid solution strengthening elements such as Cr,Mo,and N,leading to the reduction of YS to 492 MPa.After aging for 30 min and longer,the number and size of cellular precipitates increased,leading to an increase in YS(535 MPa,after aging for 120 min).
super austenitic stainless steelprecipitation behaviormechanical propertyσ phaseCr2N precipitate
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