Preliminary fatigue and fracture tests of two stainless steels after high heat load application using various heat sources

The influence of high heat load by plasma disruption on the fatigue and fracture characteristics of first wall candidate materials was experimentally studied. In order to simulate above high load application, use was made of four high power heat sources, i.e. H+ beam, neutral beam, CO2 laser beam and electron beam generators. The materials used are austenitic stainless steels type 304 and 316. The high heat load application caused many solidification cracks to the H+ and neutral beam irradiated specimens' surfaces while few solidification cracks and blow holes were observed on and just below the laser beam irradiated specimen surface. As a result of a 3-point-bend fatigue test, the fatigue strength for irradiated specimens was degraded to some extent in comparison with unirradiated ones. In spite of the difference in beam properties and radiation conditions, the fatigue strength for the irradiated specimens seemed to be within a small scatter band. The fracture test was also conducted using 3-point-bend specimens on which only the laser beam was irradiated. The fracture toughness for the irradiated specimen was the same as for the unirradiated one since the microscopic examination of the fracture surface showed no clear difference between the two of them. (orig.)