Helium effect on the structure of Fe sbnd 0.6C sbnd 16Cr sbnd 15Ni sbnd 3Mo sbnd 0.5Nb steel

The microstructure of Fe sbnd 0.6C sbnd 16Cr sbnd 15Ni sbnd 3Mo sbnd 0.5Nb stainless steel was studied by transmission elelctron microscopy (TEM) after helium implantation to 0.5-1000 appm at temperature < 100°C and post-irradiation thermal treatments at 500-1100°C for 0.03-1000 h. The results show that the main peculiarity of microstructure evolution induced by aging of helium-implanted steel, compared to unirradiated material, is the formation of a large number of fine particles in the matrix. These particles represent, mainly, the Nb(C, N) type phase which is formed in the material at helium concentrations ≫ 5 appm and at temperatures of 600-900°C. Change in the aging temperature leads to changes in particle morphology caused by the evolution of interstitial type dislocation loops. Plate-shaped particles are formed in the matrix as a result of impurity segregation at the stacking faults of Frank loops, whereas globular particles are produced in the region of dislocation cores of unfaulted loops.