Effect of Pulsed Fluxes of Deuterium Ions and Deuterium Plasma on Oxide Dispersion Strengthened Ferritic Steels

The effect of high-power pulsed fluxes of deuterium ions and deuterium plasma generated in the Plasma Focus PF-1000U device on oxide dispersion strengthened ferritic steel KP4-ODS (Fe–15 Cr–4 Al–2 W–0.35 Y2O3) was experimentally studied. When the samples were irradiated with two pulses (N = 2), the plasma flux power density was qpl ≈ 108 W/cm2 and that of ion beam qi × 109 W/cm2. At N = 9, qpl ≈ 2 ×108 W/cm2 and qi ≈ 5 × 109 W/cm2. The pulse duration of the plasma beams was τpl ≈ 100 ns and that of the ion beams τi ≈ 50 ns. It was shown that irradiation of the material in the soft mode (N = 2) leads to surface erosion due to evaporation of the material and is accompanied by the surface polishing effect. In this case, there is no significant change in the initial structural phase state of steel; only a small change in the crystal lattice parameters of solid solutions based on iron and chromium is observed. In the hard irradiation mode (N = 9), owing to the high heating of the surface layer, in addition to erosion, the material melts. In the structure of the surface layer of the ODS steel, a chromium-based solid solution disappears and only an iron-based solid solution remains, while the number of second-phase nanoparticles increases. The presence of a liquid phase formed upon exposure to fluxes of deuterium ions and deuterium plasma stimulates the possibility of complete dissolution of small (less than ~20 nm) nanoparticles of Y2O3 oxide and partial dissolution of larger (tens of nanometers) nanoparticles. Enhanced in comparison with the solid phase, the diffusion redistribution of elements in the molten surface layer contributes to the formation of Y2O3 nanoparticles and oxides of other elements that make up the ODS steel (Al2O3, Y–Al–O) upon cooling of the melt.