Tadashi Fukuda
Institute for Materials Research, Tohoku University, Sendai 980-8577Effects of morphology of carbide and nitride precipitates on the fatigue strength under pulsating tension of Fe-30 mass%Cr alloys containing 0.03 mass%C and 0.03 mass%N were investigated. Two kinds of heat treatments were adopted to obtain different types of morphology of grain boundary precipitates and that of precipitates within the grains.
The results obtained are summarized as follows:
(1) Fatigue strength of the specimens containing grain boundary carbide and nitride is lower than that of the specimens containing carbide and nitride within the grains. The difference of fatigue strength between above mentioned two different types of morphology of carbide and nitride precipitates increase with decreasing fatigue life.
(2) Fatigue strength of the specimen containing continuous, flat, and plate-like grain goundary nitride is lower than that of the specimen containing discontinuous grain boundary carbide around shorter fatigue life.
(3) Initiation of fatigue crack in the specimens containing grain boundary carbide and nitride precipitates is promoted by intergranular fracture of decohesion at the interfaces between the matrix and those precipitates.
(4) It is recommended to choose a heat treatment condition in which the formation of large, continuous, and flat grain boundary nitride is avoided.
high chromium ferritic steel, fatigue strength, carbide, nitride, morphology of second phase particle