Combined effect of thermal fatigue and creep on structure and fracture mode in the 12Kh1MF steel

Changes in the 12Kh1MF steel structure in the process of thermal fatigue were studied along with the effect of this changes on creep. Thermal fatigUe tests were carried out with 565 → 100 deg C temperature gradient in a cycle. Creep tests were conducted at 565 deg C under 15x107 Pa stress. It has been shown that thermal cycling 1.5 times drops specimen durability. This fact is explained by the instability created by substructure thermal cycling leading to acceleration of recrystallization in a cold worked matrix under the conditions of secondary creep. The material density in the process of thermal cycling increases. A sharp density decrease is observed during the long-term strength tests because of precipitation of carbides