Effects of helium implantation on hardness of pure iron and a reduced activation ferritic-martensitic steel

Helium was implanted into high purity Fe and F82H at room temperature up to 2000 appm to investigate helium effects on hardening. Ultra micro-indentation tests were performed on the specimens before and after helium implantation with loads that penetrate in 300 nm depth. After the indentation tests, the specimens were prepared with a focused ion beam (FIB) processing system for transmission electron microscopy (TEM) of the deformed regions. Results of the indentation tests indicated clearly that helium implantation caused hardening for both pure Fe and F82H. For pure Fe, it was also observed by TEM that the propagation of the plastic deformation zone formed during the indentation was limited to the helium-implanted layer, ranging from 600 to 800 nm from the incident surface.