抄録
Near-threshold fatigue crack propagation properties were investigated for Cr-Mo-V steel at elevated temperature of 200, 300 and 400°C under testing frequencies f=0.5, 5 and 50Hz. The results were compared with those for SB42 and SUS304 steels in the previous work. The main conclusion obtained are as follows : (1) At f=50Hz, Aunique ΔK-value of about 2.8MPa·m1/2 was obtained, independently of material and temperature, at high stress ratios where the closure did not occur, while ΔK increased at low stress ratios due to oxide-induced closure. (2) The crack propagation rate exceeded the value at room temperature and generally with a more pronounced degree with increasing temperature and decreasing frequency. (3) Intergranular cracking, which might be related to creep damage, was not found even at the highest temperature of 400°C and the lowest frequency of 0.5Hz in this work.
