Structural modification and erosion of plasma-irradiated tungsten and molybdenum surfaces

Data for the structural modification and erosion of plasma-irradiated tungsten and molybdenum surfaces are reported. It has been found that the irradiated specimen surface shows a relief due to nonuniform etching. It has been shown using metallographic examination that the relief of a tungsten surface irradiated at 1000 and 1500$^\circ$C is less pronounced than after irradiation at 700$^\circ$C. The surface roughness of tungsten has been found to be the highest after irradiation at 1500$^\circ$C, which is related to the formation of fine cracks. It should be noted that after irradiation by plasma flows simulating steady-state conditions, considerable erosion on irradiated tungsten and molybdenum surfaces is observed only at high temperatures. Also, it has been established that the crack size grows when the ion energy rises from 1.5 to 2.0 keV. It has been shown that tungsten irradiation by a stationary plasma forms 100- to 500-nm etch pits inside grains, and when tungsten is irradiated by an accelerating voltage of 1.6 keV, a large amount of fine pores (from 0.2 to 1.0 $\mu$m across) appear as a result of surface etching.