Abstract
Fatigue tests were carried out on S15CK tufftrided specimens at room temperature, 100, 300, 400, and 500°C under reversed axial stress.
The results obtained were summarized as follows;
(1) The fatigue limit of tufftrided steel at room temperature is about 1.4 times the value of untufftrided one.
(2) The fatigue strength of tufftrided steel at 300°C is higher than that at room temperature, but when the temperature is over 300°C, the fatigue strength becomes lower that at room temperature. The fatigue strength at 500°C is close to that of untufftrided steel at room temperature.
(3) The hardness of tufftrided steel increases after the fatigue test at every temperature tested. Especially, the increase in hardness is remarkable at the core of specimen.
(4) The microstructural observation after the fatigue test at 300°C revealed a remarkable precipitation of nitride from the position 1mm inside of the surface to the center of core.
