The effects of Ar post-bombardment and heat treatment on hardness of N implanted iron

The hardness of N implanted iron submitted to Ar post-bombardment and subse quent thermal treatment up to 600 degreesC was measured using the nanoinden tation technique. The hardness of mechanically polished iron samples was 5. 5 GPa at shallow depths. After N implantation the hardness rised to 12 GPa. Ar post-irradiation produced dissolution and reprecipitation of nitrogen p recipitates and the hardness decreased to 10 GPa. Further annealing induced differences in hardness. The hardness decreased with thermal treatment sho wing the highest values for samples with Ar distribution deeper than the N initial profile. Pop-in (tip incursions) are observed in load displacement curves after 600 degreesC/l h thermal treatment. In Ar irradiated samples, this phenomenon is observed at a different depth than for iron. (C) 2001 El sevier Science B.V. All rights reserved.