マルテンサイト・ステンレス鋼SUS403-Bの回転曲げ高温疲労現象

抄録

Rotating bending fatigue tests were carried out on a martensitic stainless steel (Type 403) at room temperature, 200, 300, 400, 450 and 500°C with a frequency of 7500 r. p. m. and the fatigue strength at 10⁸ cycles was obtained by the staircase method.
The results obtained are summarized as follows:
(1) The endurance limits were found, and the fatigue strength at 10⁷ and 10⁸ cycles were identical at 200 and 300°C and were nearly equal at room temperature and 400°C. At 450 and 500°C, the number of cycles to failure continued to increase with decreasing stress amplitude up to 108 cycles.
(2) The ratio of fatigue strength at 10⁸ cycles to 0.2% proof stress was 0.64∼0.69 at R. T.∼500°C.
(3) The coaxing effect was slightly observed in the temperature range from room temperature to 400°C.
(4) The room temperature hardness at the surface of the specimens endured 10⁸ cycles at high temperatures from 200 to 400°C was larger than that of a virgin specimen.
(5) The strengthening of the material is considered to be caused by dynamic aging during the fatigue test at 200∼400°C. This phenomenon can be pointed out as a reason why endurance limits were found and the coaxing effect was observed in this temperature range.