A Study of the Effect of Long-Term Thermal Aging on the Creep-Rupture Properties of 18Cr-9Ni Steel
Experimental investigations of the creep-rupture properties of metal of intermediate heat exchangers (IHX) from fast breeder reactor BN-600 after its operation during ∼ 170 thousands hours over temperature range of 500–550°C were carried out. IHX was produced from 18Cr-9Ni steel. To study the role of thermal aging part of the IHX metal was annealed at 1000–1050°C for 0.5 hours. Comparison of experimental results of aging metal and annealed metal was carried out and the microstructure and fractography of both materials examined. The effect of aging on the creep-rupture properties of 18Cr-9Ni steel was revealed and described by the physical and mechanical model of intergranular fracture. On the basis of experimental and calculative results an explanation of the effect of long-term aging on the mechanical short-term and creep-rupture properties of 18Cr-9Ni steel has been provided.