Low-energy hydrogen ion irradiation effect on the surface defects of powder metallurgy molybdenum

Molybdenum (Mo) and its alloy materials are used for key components such as fuel containers and first walls in future fusion energy systems due to their high melting point and excellent high-temperature strength, creep resistance, thermal conductivity, corrosion resistance and low sputtering rate. During fusion reactions, hydrogen ions come into direct contact with Mo and its alloy materials. The injection of low-energy hydrogen ions can cause serious damage to the surface and subsurface of Mo. The injection of low-energy hydrogen ions can cause serious damage to the surface and subsurface of Mo, including changes in microstructure, surface defects and surface roughness. In this paper, the irradiation damage behavior of powder metallurgy (PM) Mo under 100 eV hydrogen ion irradiation is comprehensively analyzed by scanning electron microscope, atomic force microscope and X-ray diffractometer. The results indicate that surface bubbling, corrosion, surface protrusions, and fuzzing are the main damage forms of Mo under low-energy hydrogen ion irradiation. With the increase of ion dose, some defects resembling trap caps appear inside the grains and gradually evolve into melt pits, deepening the etching behavior of the Mo surface. The damage will first preferentially occur on its own defects (such as holes), and the required dose will be greatly reduced. The surface roughness of Mo decreases first and then increases with the increase of irradiation dose. XRD analysis shows that there is no new precipitated phase in Mo after hydrogen ion irradiation, and its diffraction peak shifts to high angles. The surface of Mo exhibits radiation hardening phenomenon, and the increase in radiation dose makes the radiation hardening effect more pronounced. As the irradiation depth increases, the hardening effect of Mo gradually weakens.