It is important to investigate the effect of irradiation on the fatigue damage of high heat flux components which directly face a fusion plasma. The materials tested are 316SS and 304SS. The former is the reference first wall plate for the fusion experimental reactor. The specimen was irradiated with a high power laser beam and then a cyclic load was applied to the specimen up to fracture. The laser beam can provide only a heat flux because it is effective as a microwave only. The melt layer surface looks rough and seems to be oxidized. Although there exists no difference in fatigue strength between the irradiated 316SS and 304SS, the fatigue strength for the irradiated specimen is greatly decreased according to the quantity of irradiation. The microscopic observation was made on the section including the melt layer and on the fracture surface. The near melt surface is characterized by a blow hole, solidification cracking, and a columnar structure. This means that the melt layer was quickly cooled by heat loss under atmospheric conditions. In conclusion, the microscopic defects can cause the fatigue strength to be much degraded. Other factors such as surface roughness could be attributed to the reduction of strength.
Study of material response in disruption simulation experiments with variable irradiation duration