科研之友
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摘要
In this paper, we consider the origin of high-temperature strength of heat-resistant steels belonging to martensitic class developed on the basis of the Fe-9% Cr alloy for the boiler pipes and steam pipelines of power plants at steam temperatures of up to 620 degrees C and pressures to 300 atm. In addition, we give a brief information on the physical processes that determine the creep strength and consider the alloying philosophy of traditional heat-resistant steels. The effect of the chemical and phase composition of heat-resistant steels and their structure on creep strength is analyzed in detail. It is shown that the combination of the solid-solution alloying by elements such as W and Mo, as well as the introduction of carbides of the MX type into the matrix with the formation of a dislocation structure of tempered martensite, ensures a significant increase in creep resistance. The steels of the martensitic class withstand creep until an extensive polygonization starts in the dislocation structure of the tempered martensite("troostomartensite"), which is suppressed by V(C,N) and Nb(C,N) dispersoids. Correspondingly, the service life of these steels is determined by the time during which the dispersed nanocarbonitrides withstand coalescence, while tungsten and molybdenum remain in the solid solution. The precipitation of the Laves phases Fe(2)(W,Mo) and the coalescence of carbides lead to the development of migration of low-angle boundaries, and the steel loses its ability to resist creep.
- 出版日期2010-2
