Modification of Surfaces of Reduced-Activation Ferritic–Martensitic Steels upon Irradiation by Pulsed Deuterium Plasma with Parameters Typical for Peripheral Plasma Disruption

Reduced activation (with rapid activity decay) ferritic–martensitic steels are promising structural materials for fusion power engineering. This article discusses the capability of using them as a plasma-facing material in areas of relatively low energy load. Samples of Rusfer, Eurofer, CLAM, and F82H steels were irradiated with pulsed flows of deuterium plasma typical for peripheral plasma disruptions. Two variants of load were selected: 0.3 MJ/m2, 1 ms, i.e., the conditions under which the surfaces of these steels do not melt, and 0.6 MJ/m2, 1 ms, i.e., the conditions under which the surface layer melts. The samples were irradiated by 1–25 pulses during each load. The surface-layer modification was analyzed. It was established that if upon irradiation the surface layer of the samples melts, then already after one pulse the surface layer of Rusfer, CLAM, and F82H samples becomes wavy, and the surface of Eurofer steel remains flat until irradiation with 25 pulses with the following parameters: 0.6 MJ/m2, 1 ms. This can be related to the different compositions of the steels. The calculations demonstrate that the coefficient of surface tension in the molten layer of Eurofer steel is higher than that of Rusfer steel at the same temperature. Steel with a higher coefficient of surface tension keeps its shape better under the action of external forces.